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STORMWATER MANAGEMENT REPORT
AND
EROSION CONTROL RESULTS
7-ELEVEN
STORE 42957 – SITE 1056904
HOLLY SHELTER ROAD & BARBADOS BLVD
CASTLE HAYNE
NEW HANOVER COUNTY, NORTH CAROLINA
ORIGINAL DATE: MARCH 16, 2026
FREELAND AND KAUFFMAN, INC.
ENGINEERS * LANDSCAPE ARCHITECTS
209 WEST STONE AVE.
GREENVILLE, SC 29609
864-233-5497
TABLE OF CONTENTS
I. PROJECT NARRATIVE ...................................................................... 1
A. Executive Summary ............................................................................................................... 2
B. Construction Sequence .......................................................................................................... 3
C. Coordinating Permits ............................................................................................................ 5
D. Easements .............................................................................................................................. 5
E. Downstream Analysis ............................................................................................................ 5
II. RAINFALL DATA & METHODOLOGY ................................................ 6
III. PRE-DEVELOPMENT SUMMARY ...................................................... 7
F. Pre-Dev Weighted Curve Number Calculations ................................................................... 8
G. Pre-Dev Time of Concentration Calculations ....................................................................... 9
H. Pre-Dev Peak Flow Calculations ......................................................................................... 10
IV. POST-DEVELOPMENT SUMMARY ................................................... 11
A. Post-Dev Weighted Curve Number Calculations ............................................................... 12
B. Post-Dev Time of Concentration Calculations ................................................................... 13
C. Post-Dev Peak Flow Calculations ........................................................................................ 14
V. DETENTION POND SUMMARY ....................................................... 15
A. Water Quantity Calculations ............................................................................................... 16
B. Water Quality Calculations .................................................................................................. 17
VI. EROSION & SEDIMENT CONTROL SUMMARY ............................... 18
A. Skimmer Basin Calculations ............................................................................................... 19
VII. STORM DRAIN CALCULATIONS ..................................................... 21
A. NCDOT Calculations ........................................................................................................... 21
VIII. MISCELLANEOUS CALCULATIONS................................................. 23
APPENDIX A ............................................................................................... 1
APPENDIX B ............................................................................................... 2
APPENDIX C ............................................................................................... 3
APPENDIX D .............................................................................................. 4
APPENDIX INDEX
APPENDIX A (Site Conditions & Rainfall Data) .............................................
GIS Vicinity Map
Location Map
Site Plan
USGS 7.5-Minute Topographic Map
FEMA FIRM Flood Map
NRCS Soil Survey
NOAA Precipitation Atlas – Depth
NOAA Precipitation Atlas – Intensity
APPENDIX B (Drainage Basin Summaries) ...................................................
Pre-Development Map
Post-Development Map
Pond Section Detail
Hydraflow Results –2-YR, 10-YR, 25-YR, and 100-YR
Hydraflow Results – 1.5” WQ and 100-YR Clogged Condition
APPENDIX C (Inlet and Pipe Summaries) .....................................................
Storm Plan
Inlet Area Map
StormSewers Results – 4 in/hr, 25-YR, and 100-YR
StormSewers HGL/Profiles – 25-YR and 100-YR
NCDOT Ditch Calculations – 10-YR Design Year
NCDOT Driveway Pipe Calculations – 10-YR Design Year
APPENDIX D (Erosion Control Summaries) .................................................
Erosion Control Phase Sheets
ESC Hydraflow Results – 10-YR
ESC Hydraflow Express – Temporary Diversion
Stormwater Facility Operation & Maintenance Agreement
Page | 1
I. PROJECT NARRATIVE
This report details the stormwater management system for the proposed 7-Eleven store located
in the southwest quadrant of Holly Shelter Road and Barbados Blvd in Castle Hayne, NC within
New Hanover County (PID: R01100-008-015-000). The full lot is a recorded ±6.42 acres, with a
±5.45-acre portion set to be considered in this proposed development. The property is zoned B-2
(Regional Business District) and is within New Hanover County jurisdiction. The site is proposed
to contain a new 7-Eleven convenience store with automotive and truck fueling. Development will
include a 5,373 square foot building, fuel facilities, parking areas, driveways, utilities, stormwater
management systems, and landscaping.
The property is bordered by wooded undeveloped property to the west, commercial property to
the south, Holly Shelter Road to the north, and Barbados Blvd to the east. One full-movement
automotive only access is proposed along Barbados Blvd. Two one-way truck-only access points
are also proposed along Barbados Blvd. Offsite roadway improvements are required with this
development per direction from NCDOT and WMPO based on a traffic impact analysis.
Under existing pre-development conditions, the mostly flat parcel is divided into three drainage
areas. A majority of the runoff collects in a ditch along the eastern boundary of the property, where
an existing pipe conveys it across Barbados Blvd. Some runoff along the northern portion of the
property is collected in a roadside ditch which flows east along Holly Shelter Road. A minimal
amount of runoff sheet flows onto the adjacent western parcel. Under the proposed post-
development conditions, runoff from the site is captured by a proposed storm system, routed
through a wet detention basin, and discharged to the same pre-development collection points.
The closest downstream point of discharge would ultimately be Prince George Creek (SI-18-74-
53) within the Cape Fear watershed (HUC-030300070807). Per FEMA mapping, the site is in
Flood Zone X. The nearest water quality monitoring station is B9600000 within Prince George
Creek. The Cape Fear River Basin does not present a nutrient management strategy. There are no
404 wetlands present within the project area. No negative downstream impacts are expected with
this development.
This report also discusses the erosion control measures planned for the proposed development.
The wet detention basin footprint will serve as a temporary sediment basin for the duration of
construction.
Page | 2
A. Executive Summary
This hydraulic study for the proposed site is developed to meet New Hanover County, NCDEQ,
and NCDOT standards through the application of criteria set forth in the respective stormwater
management design manuals. As required by NCDEQ criteria, the post-development conditions
provide extended detention of the first one-and-half inch (1.5”) of runoff to be released over a
period of 2-5 days. As required by New Hanover County criteria, the post-development conditions
provide peak discharge control of the 2-year, 10-year, and 25-year, 24-hour storm events with a
peak flow rate less than the pre-development rate. As required by NCDOT criteria, the post-
development conditions provide peak discharge control of the 100-year, 24-hour storm event with
a peak flow rate less than the pre-development rate. Adherence to these standards supports that
adjacent property or downstream facilities will not be negatively impacted.
Provided is a summary of peak flow rates (cfs) in pre and post-development conditions:
Storm Event
Pre-Development Post-Development
Analysis
Point #1
Analysis
Point #2
Analysis
Point #3
Analysis
Point #1
Analysis
Point #2
Analysis
Point #3
2-year 1.43 0.00 0.00 1.37 0.00 0.00
10-Year 4.29 0.05 0.09 4.22 0.07 0.12
25-Year 6.72 0.25 0.26 5.69 0.19 0.34
100-Year 11.82 1.13 0.77 10.42 0.51 0.92
Provided is a summary of the wet detention pond during post-development conditions:
Storm Event
Post-Development Pond
Max Elevation
(ft.)
Max
Storage
(cf)
Peak Flow Rate
(cfs)
1.5" WQ 23.16 11,857 0.08
2-year 23.66 22,048 1.31
10-Year 24.35 37,639 4.07
25-Year 24.83 49,687 5.43
100-Year 25.63 71,455 10.02
100-Year Clogged 25.79 75,930 19.31
Complete storage is provided for the 1.5” rainfall water quality event, with a provided drawdown
time of 2-5 days, to adhere to water quality standards. A staged concrete outlet structure will
regulate discharge from the wet detention basin for larger storm events, providing overbank flood
protection and extreme flood protection. As indicated in the above table, the post-development
discharge for Analysis Point #1 will be managed, as required, under post-development conditions
for the 2-yr, 10-yr, 25-yr, and 100-yr, 24-hr duration storm events. Other analysis points present
minimal increases which should fall within an acceptable range due to the low volumes.
Onsite pipe sizing was performed using the 25-yr storm event. Culvert sizing was performed using
the 25-yr storm event. The 100-yr storm event was checked to ensure no hazardous conditions for
proposed buildings, structures, roadways, or downstream facilities. Since the overall site presents
no increase in post-development discharge, no adverse downstream impacts are expected.
Page | 3
B. Construction Sequence
PHASE IA
1. CONTRACTOR SHALL OBTAIN ALL APPROPRIATE PERMITS REQUIRED FOR
DEMOLITION AND LAND DISTURBANCE ACTIVITIES.
2. CONTRACTOR SHALL CONTACT NEW HANOVER COUNTY TO SCHEDULE A PRE-
CONSTRUCTION MEETING AT (252)-636-6618.
3. INSTALL TEMPORARY DRIVEWAY CULVERT AND STABILIZED CONSTRUCTION
ENTRANCE/EXIT.
4. INSTALL SWPPP ENTRANCE SIGN, WHICH SHALL PROVIDE A PERMIT DOCUMENT
BOX AND RAIN GUAGE.
5. INSTALL TREE PROTECTION FENCE.
6. CLEAR & GRUB ONLY AS NECESSARY TO INSTALL SILT FENCE AND SILT FENCE
OUTLETS. INSTALL SILT FENCE AND SILT FENCE OUTLETS AS SHOWN.
7. NO CLEARING SHOULD OCCUR UNTIL ALL PERIMETER CONTROLS ARE INSTALLED.
8. LOCATE (AND MARK ON THE SWPPP PLAN) THE LOCATION OF THE TOPSOIL
STOCKPILE AREA. PROVIDE SILT FENCE AND TEMPORARY SEEDING AS NOTED ONCE
CLEARED IN PHASE 1B.
9. CLEAR & GRUB SITE ONLY AS NECESSARY TO INSTALL THE SEDIMENT BASIN IN
PHASE 1B.
10. CONTINUALLY INSPECT AND MAINTAIN ALL BMPS. REPAIR, REPLACE, AND ADD
BMPS AS NEEDED.
PHASE 1B
1. INSTALL OUTFALL PIPE, STRUCTURES, AND CONNECTING DRIVEWAY CULVERTS.
UTILIZE A TEMPORARY GRATE ON THE OUTLET MANHOLE UNTIL THE SEDIMENT
BASIN IS INSTALLED. INSTALL INLET PROTECTION. TRANSITION TO MANHOLE COVER
IMMEDIATELY UPON SEDIMENT BASIN COMPLETION.
2. INSTALL SEDIMENT BASIN WITH PERMANENT OUTFALL STRUCTURE, OUTFALL
PIPE, ANTI-SEEP COLLARS, AND EMERGENCY SPILLWAY AS INDICATED ON THE PLANS.
UTILIZE DEWATERING AS NECESSARY BASED ON PROVIDED DETAILS.
3. IMMEDIATELY STABILIZE ALL SEDIMENT BASIN SLOPES WITH EROSION CONTROL
BLANKETS AND TEMPORARY SEEDING.
4. CONTACT NEW HANOVER COUNTY TO SCHEDULE AN INSPECTION AT (910) 798-7139
PRIOR TO ANY ADDITIONAL CLEARING & GRUBBING.
5. INSTALL BERMS TO DIRECT RUNOFF TOWARDS THE SEDIMENT BASIN AS
NECESSARY. INSTALL ROCK CHECKS FOR ANY CONCENTRATED FLOWS.
6. CLEAR & GRUB SITE, ENSURING ANY TEMPORARY STOCKPILES FOLLOW DESIGN
GUIDANCE.
7. INSTALL TEMPORARY DIVERSION DITCHES TO DIRECT RUNOFF TOWARDS THE
SEDIMENT BASIN AS SHOWN, ADJUST GRADE TO FILL LOW AREAS AND DIRECT
RUNOFF TOWARDS SEDIMENT BASIN OR DIVERSION DITCHES.
8. INSTALL CONCRETE WASHOUT ONCE CLEARING ALLOWS.
9. CONTINUALLY INSPECT AND MAINTAIN ALL BMPS. REPAIR, REPLACE, AND ADD
BMPS AS NEEDED.
10. AS GRADING PROGRESSES, ADJUST DIVERSION DITCHES AND ANY TEMPORARY
BERMS TO DIRECT RUNOFF TOWARDS THE SEDIMENT BASIN.
Page | 4
PHASE 2
1. BEGIN MASS GRADING OF SITE. APPLY PERMANENT SEEDING & SODDING TO ANY
AREAS THAT ARE BROUGHT TO THEIR FINAL GRADE, AS SOON AS THEY ARE
COMPLETE. DO NOT WAIT UNTIL JOB COMPLETION TO PERMANENTLY STABILIZE
DISTURBED AREAS. ADD EROSION CONTROL BLANKETS AS NEEDED FOR ALL AREAS
WITH SLOPES THAT EXCEED 3:1.
2. UTILIZE TEMPORARY SWALES, BERMS, AND ROCK CHECKS, AS NECESSARY, TO
DIRECT RUNOFF TO SEDIMENT BASIN. IT IS EXPECTED THESE WOULD ONLY BE
NECESSARY PRIOR TO RAIN EVENTS.
3. INSTALL STORM DRAIN (WITH INLET PROTECTION) AND UTILITIES OF SEWER,
WATER, ELECTRIC, COMMUNICATION, & NATURAL GAS.
4. BEGIN CONSTRUCTION OF BUILDING PAD & STRUCTURES.
5. IMMEDIATELY PLACE STONE BASE ON FUTURE IMPERVIOUS AREAS ONCE SUB-
GRADE ELEVATIONS ARE ACHIEVED.
6. INSTALL SIDEWALKS AND CURB & GUTTER. PREPARE SITE FOR PAVING.
7. PAVE AND STRIPE SITE.
8. TRANSITION TO APPROPRIATE INLET PROTECTION DEVICES AS DIRECTED WHEN
SURROUNDING GROUND COVER CHANGES FROM PERVIOUS TO IMPERVIOUS.
9. ENSURE PERMANENT SEEDING & PLANTING IS APPLIED PER LANDSCAPE PLAN.
10. CONTINUALLY INSPECT AND MAINTAIN ALL BMPS. REPAIR, REPLACE, AND ADD
BMPS AS NEEDED.
11. INITIATE PERMIT CLOSURE PROCEDURES WITH NEW HANOVER COUNTY AT (910)
798-7139 PRIOR TO CONVERTING POND TO FINAL CONFIGURATION.
12. UPON STABILIZATION OF THE SITE, INSPECT ALL STORM DRAIN SYSTEMS FOR
SEDIMENT ACCUMULATION AND REMOVE ANY SEDIMENT, TRASH, BUILDUP, ETC.
13. CONVERT TEMPORARY SEDIMENT BASIN TO PERMANENT STORMWATER BASIN
PER POND SECTION DETAIL. REMOVE SEDIMENT FROM THE POND, PERFORM AS-
BUILT SURVEY, SCHEDULE FINAL INSPECTION, AND COORDINATE ANY REPAIRS OR
SERVICES NECESSARY TO FILE NOTICE OF TERMINATION (NOT).
14. ENSURE PERMANENT SEEDING & PLANTING IS INSTALLED PER LANDSCAPE PLAN,
INCLUDING THE VEGETATED SHELF WITHIN THE POND.
11. CONTINUE PERMIT CLOSURE PROCEDURES WITH NEW HANOVER COUNTY AT (910)
798-7139 PER NCG01 CERTIFICATE OF CLOSURE REQUIREMENTS.
12. CONTACT NEW HANOVER COUNTY FOR FINAL INSPECTION AND OWNER FOR
COORDINATION OF FILING THE NOTICE OF TERMINATION (NOT).
Page | 5
C. Coordinating Permits
This Stormwater Management Report and appropriate plan sets have been submitted to multiple
entities for required permitting related to hydraulics and hydrology:
NCDEQ Erosion and Sediment Control Plan Review
NCDEQ eNOI
NCDEQ Post-Construction Stormwater Plan Review
New Hanover County MS4 Permitting (Land Disturbance & Stormwater)
NCDOT Driveway Encroachment Permit
D. Easements
There is a right-of-way (ROW) dedication tied to the NCDOT Driveway Encroachment Permit, as
required by the roadway improvements presented. There are no other stormwater related
easements for this project.
E. Downstream Analysis
There is no downstream analysis presented, as the proposed stormwater features appropriately
manage bankfull and flooding conditions. Analysis of the 100-yr storm event presents no
immediate danger to structures or downstream facilities.
Page | 6
II. RAINFALL DATA & METHODOLOGY
The calculations within this report are based on rainfall data as determined by the National
Oceanic and Atmospheric Administration (NOAA) Precipitation Frequency Data Server (PFDS).
The 24-hour precipitation amounts for the site, as outlined by NOAA Atlas 14, Volume 2, Version
3 for Castle Hayne, NC:
2-Year Storm Event: 4.62 inches
10- Year Storm Event: 7.17 inches
25- Year Storm Event: 9.00 inches
100- Year Storm Event: 12.50 inches
NOAA Atlas tables are provided for reference in Appendix A.
Based on the U.S. Soil Conservation Service (SCS) the rainfall pattern for this area is considered
Type III, which represents areas bordering the Gulf of Mexico and Atlantic seaboard where
tropical storms and hurricanes generate heavy runoff.
Software and Calculation Tools
TR-55 (Win TR-55, Version 1.00.00): TR-55 is used to calculate the Runoff Curve Number and
the Time of Concentration for each of the drainage basins in both the pre- and post-development
conditions. TR-55 allows for several distinct land-use characteristics and runoff flow properties
to be considered.
Hydraflow Hydrographs (Version 2024): Hydraflow Hydrographs, a computer model based on
the SCS Method, is used to generate the pre-developed and post-developed runoff hydrographs,
using the runoff curve number and time of concentration values generated by TR-55.
Hydrographs also models extended detention basins, outlet structures, and provides the routing
for each storm event through the pond system.
Hydraflow StormSewers (Version 2024): Hydraflow StormSewers, a computer model based on
the Standard Step Method and the Rational Method, is used to analyze storm sewer systems,
including pipe data, inlet data, and hydraulic grade line information. The program uses
anticipated flows, inlet configurations, pipe features, and downstream qualities to provide full
analysis.
Hydraflow Express (Version 2024): Hydraflow Express, a computer model based Manning’s
Equation and HDS-5 (Hydraulic Design of Highway Culverts), is used to analyze storm sewer
systems, including culverts, channels, and inlets. The program uses provided geometry to
calculate capacity.
Page | 7
III. PRE-DEVELOPMENT SUMMARY
The proposed development is situated on a ±6.42-acre tract at the southwest quadrant of Holly
Shelter Road and Barbados Blvd in Castle Hayne, NC within New Hanover County (PID: R01100-
008-015-000). Per a topographic survey by LJA Surveying, the property is undeveloped. Site
elevation contours vary from 11’ to 32’ with a majority of the property being flat, except for an
existing ditch along the eastern boundary of the property. The highest elevation is an outlier,
where a small mound is present. The lowest site elevation is also an outlier, found at the
northwestern boundary, where a pocket depression exists. A majority of the site drains towards
an existing low point and 30”RCP pipe at the eastern boundary along Barbados Blvd. This low
point and other areas representative of runoff leaving the site along the property boundary act as
the Analysis Points for pre-development and post-development analysis. Runoff eventually leads
to Prince George Creek within the Cape Fear watershed (HUC-030300070807). There are no 404
wetlands within the project area.
The land cover consists entirely of wooded areas with light underbrush in good condition. Soil
conditions vary throughout the site, with mostly sandy soil that presents hydrologic qualities of
HSG A or HSG D. USDA Soil Mapping is provided in Appendix A.
The pre-development conditions have been analyzed as three drainage areas and three analysis
points. These drainage areas include the entire project site:
Pre-Development Area 1: This drainage area consists of ±2.55-acres, covering the
southern half of the project site. The ground cover is comprised of wooded area. This area
drains via sheet flow and shallow concentrated flow to Analysis Point #1 along the eastern
boundary. Beyond the Analysis Point, this flow would be conveyed through an existing 30”
RCP culvert.
Pre-Development Area 2: This drainage area consists of ±1.64-acres, covering the
northern boundary of the project site. The ground cover is comprised of wooded area. This
area mostly drains via sheet flow to an existing low point that would impound runoff.
Minimal runoff would flow to the roadside ditch along Holly Shelter Road, considered
Analysis Point #2. Beyond the Analysis Point this flow would be conveyed via roadside
ditch.
Pre-Development Area 3: This drainage area consists of ±0.28-acres, covering a
portion of the western boundary of the project site. The ground cover is comprised of
wooded area. This area drains via sheet flow onto the adjacent property, considered
Analysis Point #3.
A Pre-Development Area Map is provided in Appendix A.
Page | 8
F. Pre-Dev Weighted Curve Number Calculations
A weighted Curve Number (CN) has been determined for each drainage area in this report. CN
values are assigned based on TR-55 guidance, which estimates the CN as a function of hydrologic
soil group (HSG), cover type, treatment, hydrologic condition, antecedent runoff condition (ARC),
and impervious area in the catchment. A weighted average of CN components within the drainage
boundary is calculated so that a single CN is representative of the entire drainage basin. Provided
are the individual components and the weighted curve number for each drainage basin:
Pre-Development Area 1 :
Woods
Good condition
HSG A: 1.06 Ac
Woods
Good condition
HSG D: 1.50 Ac
CN = 30 CN = 77
Total Land Area = 2.55 Acres
Weighted Runoff Curve Number = 58
Pre-Development Area 2 :
Woods
Good condition
HSG A: 1.64 Ac
CN = 30
Total Land Area = 1.64 Acres
Weighted Runoff Curve Number = 30
Pre-Development Area 3 :
Woods
Good condition
HSG A: 0.23 Ac
Woods
Good condition
HSG D: 0.05 Ac
CN = 30 CN = 77
Total Land Area = 0.28 Acres
Weighted Runoff Curve Number = 37
Page | 9
G. Pre-Dev Time of Concentration Calculations
A time of concentration has been determined for each drainage area in this report. Runoff times
are assigned based on TR-55 guidance, which consider three separate flow characteristics to
determine the longest timed path. Sheet flow defines typical overland flow over open areas.
Shallow concentrated flow is used for any overland flow over 100’, assuming the flow has
concentrated. Open-channel flow describes flow through ditches and pipes. TR-55 calculates
travel times for each type of flow, given parameters including slope, cover/roughness, and cross-
sectional area. Provided are the individual components and the time of concentration for each
drainage basin:
Pre-Development Area 1 :
Sheet Flow
100 feet @ 1.00%
Light Underbrush n=0.40
Shallow Concentrated Flow
286 feet @ 1.00%
Unpaved Surface
No Channel Flow
Tc = 24.50 min. Tc = 2.95 min. Tc = 0.00 min.
Total Time of Concentration = 27.45 min.
Pre-Development Area 2 :
Sheet Flow
100 feet @ 3.50%
Light Underbrush n=0.40
Shallow Concentrated Flow
238 feet @ 5.78%
Unpaved Surface
No Channel Flow
Tc = 14.29 min. Tc = 1.02 min. Tc = 0.00 min.
Total Time of Concentration = 15.3 min.; User time of 60 min. to account for
minimal flow that would leave site
Pre-Development Area 3 :
Sheet Flow
62 feet @ 3.00%
Light Underbrush n=0.40
No Shallow Concentrated
Flow
No Channel Flow
Tc = 10.37 min. Tc = 0.00 min. Tc = 0.00 min.
Total Time of Concentration = 10.37 min.
Page | 10
H. Pre-Dev Peak Flow Calculations
The NRCS hydrograph method is used to calculate runoff volume, size detention facilities, and
determine peak flow from storm rainfall. This widely accepted method considers curve numbers,
time of concentrations, and rainfall-runoff relationships to estimate direct runoff. A hydrograph
is generated showing rate of flow versus time for each drainage area. Drainage areas are
considered individually or combined and can be routed through ponds or reaches as necessary.
Drainage areas, pond outfalls, and reaches can be combined at an analysis point to allow for
comparison. For this project, the 1.5” WQ, 2-yr, 10-yr, 25-yr, and 100-yr storm events were
considered for analysis. Provided are the peak flow rates of runoff for each drainage basin and
analysis point.
Storm Event
Pre-Development
Pre-Dev
Area 1
Pre-Dev
Area 2
Pre-Dev
Area 3
2-year 1.43 0.00 0.00
10-Year 4.29 0.05 0.09
25-Year 6.72 0.25 0.26
100-Year 11.82 1.13 0.77
Pre-Development hydrographs are provided in Appendix B.
Page | 11
IV. POST-DEVELOPMENT SUMMARY
The proposed development places FFE at 29.00’ and presents contours varying from 29’ to 18’.
The building will sit on the highest elevation. The lowest site elevations will be the bottom of a wet
pond, which will be below the water table elevation. The existing low point in the northwest corner
will be filled during early phases, as runoff will be captured and directed to a wet detention pond.
The outfall location will be the existing 30” RCP culvert along the eastern boundary. The same
Analysis Points are considered for pre-development and post-development analysis. Runoff
eventually leads to Prince George Creek within the Cape Fear watershed (HUC-030300070807).
There are no 404 wetlands within the project area.
The land cover consists entirely of impervious or Bermuda grassed areas as good condition. Soil
conditions vary throughout the site, with mostly sandy soil that presents hydrologic qualities of
HSG A or HSG D. It is assumed that the fill material will improve hydrologic qualities within the
on-site areas. USDA Soil Mapping is provided in Appendix A.
The post-development conditions have been analyzed as four drainage areas and three analysis
points. These drainage areas include the entire project site:
Post-Development Area 1A: This drainage area consists of ±3.80-acres, including the
portion of the built upon area set to be captured and routed to the proposed SCM. The
ground cover is comprised of Bermuda grass and impervious area. This area drains via
sheet flow, shallow concentrated flow, and pipe flow to the wet detention pond, Pond A.
Post-Development Area 1B: This drainage area consists of ±0.28-acres, including the
eastern portion of the built upon area set to bypass the proposed SCM. The ground cover
is comprised of Bermuda grass and impervious area. This area drains via sheet flow to
Analysis Point #1. Beyond the Analysis Point, this flow would be conveyed through an
existing 30” RCP culvert.
Post-Development Area 2: This drainage area consists of ±0.14-acres, including the
northern portion of the built upon area set to bypass the proposed SCM. The ground cover
is comprised of Bermuda grass. This area drains via sheet flow to an existing roadside ditch
along Holly Shelter Road, considered Analysis Point #2. Beyond the Analysis Point this
flow would be conveyed via roadside ditch.
Post-Development Area 3: This drainage area consists of ±0.25-acres, including the
western portion of the built upon area set to bypass the proposed SCM. The ground cover
is comprised of Bermuda grass. This area drains via sheet flow onto the adjacent property,
considered Analysis Point #3.
The bulk of analysis is concerning Analysis Point #1, as it acts as the primary outfall for
the wet detention pond and all impervious built upon areas. Beyond this point, runoff is
conveyed via a 30” RCP culvert, eventually leading to Prince George Creek.
A Post-Development Area Map is provided in Appendix A.
Page | 12
A. Post-Dev Weighted Curve Number Calculations
A weighted Curve Number (CN) has been determined for each drainage area in this report. CN
values are assigned based on TR-55 guidance, which estimates the CN as a function of hydrologic
soil group (HSG), cover type, treatment, hydrologic condition, antecedent runoff condition (ARC),
and impervious area in the catchment. A weighted average of CN components within the drainage
boundary is calculated so that a single CN is representative of the entire drainage basin. Provided
are the individual components and the weighted curve number for each drainage basin:
Post-Development Area 1A :
Open Space/Grass,
Good condition
HSG A: 0.97 Ac
Impervious
2.83 Ac
CN = 39 CN = 98
Total Land Area = 3.80 Acres
Weighted Runoff Curve Number = 83
Post-Development Area 1B :
Open Space/Grass,
Good condition
HSG A: 0.12 Ac
Open Space/Grass,
Good condition
HSG D: 0.11 Ac
Impervious
0.04 Ac
CN = 39 CN = 80 CN = 98
Total Land Area = 0.28 Acres
Weighted Runoff Curve Number = 65
Post-Development Area 2:
Open Space/Grass,
Good condition
HSG A: 0.14 Ac
CN = 39
Total Land Area = 0.14 Acres
Weighted Runoff Curve Number = 39
Post-Development Area 3:
Open Space/Grass,
Good condition
HSG A: 0.25 Ac
CN = 39
Total Land Area = 0.25 Acres
Weighted Runoff Curve Number = 39
Page | 13
B. Post-Dev Time of Concentration Calculations
A time of concentration has been determined for each drainage area in this report. Runoff times
are assigned based on TR-55 guidance, which consider three separate flow characteristics to
determine the longest timed path. Sheet flow defines typical overland flow over open areas.
Shallow concentrated flow is used for any overland flow over 100’, assuming the flow has
concentrated. Open-channel flow describes flow through ditches and pipes. TR-55 calculates
travel times for each type of flow, given parameters including slope, cover/roughness, and cross-
sectional area. Provided are the individual components and the time of concentration for each
drainage basin:
Post-Development Area 1A :
Sheet Flow
73 feet @ 3.22%
Bermuda n=0.41
No Shallow Concentrated
Flow
No Channel Flow
Tc = 11.71 min. Tc = 0.00 min. Tc = 0.00 min.
Total Time of Concentration = 11.71 min.
Post-Development Area 1B:
Minimal Sheet Flow No Shallow Concentrated
Flow
No Channel Flow
Tc = 5.00 min. Tc = 0.00 min. Tc = 0.00 min.
Total Time of Concentration = 5.00 min. minimum used
Post-Development Area 2 :
Minimal Sheet Flow No Shallow Concentrated
Flow
No Channel Flow
Tc = 5.00 min. Tc = 0.00 min. Tc = 0.00 min.
Total Time of Concentration = 5.00 min. minimum used
Post-Development Area 3 :
Minimal Sheet Flow No Shallow Concentrated
Flow
No Channel Flow
Tc = 5.00 min. Tc = 0.00 min. Tc = 0.00 min.
Total Time of Concentration = 5.00 min. minimum used
Page | 14
C. Post-Dev Peak Flow Calculations
The NRCS hydrograph method is used to calculate runoff volume, size detention facilities, and
determine peak flow from storm rainfall. This widely accepted method considers curve numbers,
time of concentrations, and rainfall-runoff relationships to estimate direct runoff. A hydrograph
is generated showing rate of flow versus time for each drainage area. Drainage areas are
considered individually or combined and can be routed through ponds or reaches as necessary.
Drainage areas, pond outfalls, and reaches can be combined at an analysis point to allow for
comparison. For this project, the 2-yr, 10-yr, 25-yr, and 100-yr storm events were considered for
analysis. Provided are the peak flow rates of runoff for each drainage basin and analysis point.
Storm Event
Post-Development
Post-Dev
Area 1A Pond A Post-Dev
Area 1B
Post-Dev
Area 1
Post-Dev
Area 2
Post-Dev
Area 3
2-year 10.50 1.31 0.42 1.37 0.00 0.00
10-Year 18.94 4.07 1.02 4.22 0.07 0.12
25-Year 25.00 5.43 1.50 5.69 0.19 0.34
100-Year 36.50 10.02 2.46 10.42 0.51 0.92
Post-Development hydrographs are provided in Appendix B.
Page | 15
V. DETENTION POND SUMMARY
A wet pond is proposed to detain stormwater runoff and control the peak discharge rate. As a
Stormwater Control Measure (SCM), this facility also provides water quality treatment. The wet
pond SCM has been designed according to the technical specification and design criteria provided
in the NCDEQ Stormwater Design Manual and the state’s Minimum Design Criteria (MDC). This
SCM is also designed in accordance with the minimum water quality and quantity performance
standards of New Hanover County, as outlined in the Stormwater Design Manual.
The wet pond is designed to capture and provide extended detention of the first one and half inch
(1.5” WQv) of runoff, to be released over a period of 2-5 days, allowing for the treatment of TSS
through dilution and settling at a 90% removal rate. The wet pond also provides over-detention
of captured drainage areas (Post-Dev Area 1A), controlling the peak discharge rates for the 2-yr,
10-yr, and 25-yr, 24-hour storm events to protect downstream channels. Additional storm events
have been provided as further support. The proposed SCM manages the 100-yr, 24-hour storm
without negatively impacting adjacent property or downstream facilities. The proposed SCM also
manages the 100-yr, 24-hour storm event in a clogged condition, with the emergency spillway
handling the critical situation.
Provided is a summary of peak flow rates (cfs) in pre and post-development conditions:
Storm Event
Pre-Development Post-Development
Analysis
Point #1
Analysis
Point #2
Analysis
Point #3
Analysis
Point #1
Analysis
Point #2
Analysis
Point #3
2-year 1.43 0.00 0.00 1.37 0.00 0.00
10-Year 4.29 0.05 0.09 4.22 0.07 0.12
25-Year 6.72 0.25 0.26 5.69 0.19 0.34
100-Year 11.82 1.13 0.77 10.42 0.51 0.92
Provided is a summary of the wet detention pond during post-development conditions:
Storm Event
Post-Development Pond
Max Elevation
(ft.)
Max
Storage
(cf)
Peak Flow Rate
(cfs)
1.5" WQ 23.16 11,857 0.08
2-year 23.66 22,048 1.31
10-Year 24.35 37,639 4.07
25-Year 24.83 49,687 5.43
100-Year 25.63 71,455 10.02
100-Year Clogged 25.79 75,930 19.31
A Pond Section Detail is provided in Appendix B.
Page | 16
A. Water Quantity Calculations
SCMs are designed to meet NCDEQ and New Hanover criteria. New Hanover criteria is outlined
in Table 2-10 within the stormwater manual. SCMs shall be constructed and maintained
according to NCDEQ and New Hanover County criteria, as outlined in the ordinance.
Key Pond Dimensions:
o Bottom of Pond: 17.00’
o Main Pool: 22.50’
o Vegetated Shelf: 22.50’-23.00’; 6’ wide
o Top of Pond: 26.50’
o Spillway: 25.58’; 75’ wide
o Forebay: Area = 2,164 sf, Volume = 3,748 cf
o Main Pool: Area = 8,213 sf, Volume = 29,218 cf
Calculations:
Main Pool Surface Area & Volume (SA/DA Method)
o ℎ = % .
. = 76.08%
o Using Table 2: Coastal SA/DA Table (Adapted from Driscoll, 1986):
3.5’ main pool depth and linear interpolation provides SA/DA = 4.90%
o
= 4.90% ,#ℎ $% = 3.72 (), * +() % ( ,*%- = 7,983 +, . /
Main Pool Depth
o $ 01 =022
22 ,#ℎ 344 5 + . 5 (6/ %44 ( ( + . 5
o 7 (55 4 6/: $ 01 = 9, :
, : = 3.56
<, meeting 3’ depth required for SA/DA method
o Bottom of pond elevation provided is 17.0’, providing one foot beyond the design bottom
elevation for sediment storage.
Forebay Sizing
o Forebay volume shall be 15-20% of the volume in the main pool
o 7 (55 4 6/:3% =
, =
9, : = 13%, although slightly below the desired percentages, the
auxiliary ponds feeding into the forebay will act as additional attenuation, allowing the
desired sedimentation to occur.
Stage Storage:
Elevation Surface
Area (SF)
Cumulative
Volume (CF)
22.50 16,834 0
23.00 17,541 8,594
24.00 23,311 29,020
25.00 26,307 53,829
26.00 29,418 81,691
26.50 31,290 96,868
Page | 17
B. Water Quality Calculations
SCMs that are designed, constructed, and maintained in accordance with the NCDEQ and MDC
criteria are presumed to meet the minimum water quality and quantity performance standards of
New Hanover County, as outlined in the ordinance.
Calculations:
The Simple Method ?0 = 0.05 + 0.9 = 0.05 + ,0.9 ∗ 0.7447- = 0.7203
ℎ = % B2.83 ()
3.80 ()= 74.47%C
$3 = ?0 ∗ ?D ∗ % ∗ 3630 = 0.7203 ∗ 1.5 ∗ 3.80 ∗ 3630 = 14,903 +E
, . / ℎ ?D = $ F6 E / Eℎ ,1.5"-
Drawdown Narrative
The design volume, DV, is the volume of runoff that must be controlled for the design storm. A
hydrograph producing this volume was generated for modeling purposes. The resulting maximum
pond elevation was 23.16’, with a low-flow 2” orifice controlling drawdown. According to
Hydraflow analysis, low-flow orifice presents a peak flow of 0.075 cfs and will drain the design
volume 64.3 hours after peak detention, or approximately 2.7 days.
TSS Removal
Wet ponds designed with 24-hours of extended detention and a 3:1 ratio of permanent pool
volume to the WQv runoff volume provide a 90% TSS removal rate, per NCDEQ and supported
by NJDEP guidance.
Page | 18
VI. EROSION & SEDIMENT CONTROL SUMMARY
Installation and maintenance of sufficient erosion control practices is required by law to retain
sediment within the boundaries of the project site. During construction, the person financially
responsible for site development is responsible for maintenance of the erosion and sedimentation
control practices installed. After construction is complete, responsibility passes to the landowner
or the person managing the land. The erosion and sedimentation control plan provides
information regarding construction sequencing, soil types, best-management practices (BMPs),
and maintenance requirements. Design and implementation is based on the NCDEQ Erosion and
Sediment Control and Design Manual. The 10-yr, 24-hour duration storm is the basis for design.
Erosion and sediment control is presented through a 3 Phase construction sequence. The total
disturbed area, inclusive of both on-site and offsite areas, is ±5.03-acres. Phase IA involves
installation of perimeter controls and initial site preparation practices, including but not limited
to: a construction entrance, silt fence, silt fence outlets, and tree protection fencing. Phase IB
involves installation of sediment control devices meant to provide impoundment and peak flow
control, which includes: temporary diversions and skimmer basins. Additional measures are also
installed, including a stockpile area and concrete washout structure. Phase II involves transition
to mass grading, installation of storm drains, installation of utilities, and transition to final ground
cover. As the site is brought to grade, temporary seeding and permanent ground cover shall be
installed. Inlet protection should be installed and then adjusted as necessary in paved areas. All
BMPs shall be maintained and inspected as noted in the plan set. All inspections and ESC closeout
documentation shall be completed before transitioning to the final pond configuration. All
stormwater facilities shall be cleared of sediment during the transition, and final groundcover
should be established per the Landscape Plan.
Page | 19
A. Skimmer Basin Calculations
Sediment basins are designed during construction phases to provide an area for runoff to pool,
allowing sediment to settle. Dewatering is achieved by draining from the top of the water column
at a controlled rate slower than incoming runoff. Runoff during construction will be directed to a
proposed skimmer basin, which will match the footprint of the final detention pond for ease of
construction. Upon installation of the skimmer basin in Phase IB, the storm drain system and site
grading will proceed. As inlets are installed, inlet protection shall be provided. Once the site is
substantially stabilized with stone and vegetation per the landscape plan, the skimmer basin can
be cleared of sediment and converted to a wet detention pond. The storm system shall be
thoroughly cleared of sediment accumulation before final inspection.
Key Skimmer Pond Dimensions:
o Bottom of Pond: 22.50’
o Top of Pond: 26.00’
o Surface Area: 17,464 sf
o Volume: 52,055 cf
Baffles are proposed per sediment basin design standards. The L/W ratio of the primary pond
section is approximately 4.5:1. Additional details are provided within the plan sheet, including but
not limited to: spillway location, cleanout elevation, outlet structure details, and outlet protection.
Calculations:
Minimum Volume 3 = 1,800 )+ () = 1,800 )+ ∗ 4.06 () = 7,308 )+, . /
The skimmer basin provides the required sediment storage at elevation 23.10’.
Minimum Surface Area *% = 325 + )+ + H:I (J 6+5 #
H:I = K :I% = 0.50 ,L( Fℎ 5-∗ 9.61
6
ℎ ∗ 4.06 () = 19.51 )+
*% = 325 + ∗ 19.51 = 6,341 +, . /
The skimmer basin provides a surface area of 17,464 sf.
Drawdown Rate
M(N $ (#/ #6 ?(E =7,308 )+
3 /(O = 2,436
)+
/(O = 0.028 )+
A 2” Faircloth skimmer with a 1.5” orifice has been selected to provide this rate.
Any skimmer design that dewaters from the surface at this controlled rate is acceptable.
Basin Capacity
The system must control the 10-yr storm event, utilizing the spillway if necessary. An ‘Erosion
Control Configuration’ is provided for the outlet control structure. Based on Hydraflow analysis,
the 10-yr storm event is managed with a maximum elevation of 25.21, supplying sufficient
capacity to ensure proper sedimentation.
Erosion control hydrographs are provided in Appendix D
Page | 20
Temporary Diversion
Temporary Diversion A:
H:I = K :I% = 0.50 ,L( Fℎ 5-∗ 9.61
6
ℎ ∗ 2.34 () = 11.25 )+
Temporary Diversion B:
H:I = K :I% = 0.50 ,L( Fℎ 5-∗ 9.61
6
ℎ ∗ 0.325() = 1.56 )+
The above peak flows were used to design an appropriately sized temporary diversion.
Hydraflow Express analysis is provided in Appendix E.
Page | 21
VII. STORM DRAIN CALCULATIONS
A pipe modeling program, Hydraflow Storm Sewers, has been used to generate sizing calculations
for all stormwater pipes and inlets. Per New Hanover County, inlet design is based on the rational
method during a 4-in/hr and 25-year storm event. These calculations show total flow for each
pipe section, velocity, hydraulic grade elevations, and spreads at each inlet. The 100-year storm
event was checked to ensure no adverse impacts are presented as related to local flooding and
hazards to adjacent structures and/or property.
An Inlet Area Map has been provided in Appendix C. Note that the Inlet Area Map provides the
rational runoff coefficient per inlet area. New Hanover County utilizes a frequency factor of 1.1 for
25-year events and 1.25 for 100-year events up to a maximum coefficient of 1.0.
The outfall pipes have been assumed to present a starting HGL equal to the wet pond elevation of
the 25-yr, 24-hr storm event, which is 25.08. All HGL elevations are below the rim elevations.
Hydraflow Storm Sewers calculates ‘Capacity Full’ using Manning’s equation for full flow. This
equation assumes the slope of the Energy Grade Line (EGL) is equal to the slope of the pipe and
the flow depth is equal to the diameter of the pipe. As proposed, certain pipes may flow under a
surcharged condition, meaning the HGL is above the crown of the pipe. This creates a head and
puts these sections under pressure – meaning EGL becomes greater than the pipe slope and a
flow greater than the calculated ‘Capacity Full’ is observed. This phenomenon is common and
expected under these conservative conditions.
A. NCDOT Calculations
According to the NCDOT Guidelines for Drainage Studies and Hydraulic Design, Section 11.2,
roadside ditches should provide capacity for the 10-yr, 24-hr storm event. These ditches also need
to be evaluated for stability using shear stress analysis. The downstream ditch section should be
checked to ensure there is a smooth transition and capacity for flow.
Ditch Calculations:
Capacity
M(66 6F< P. (E 6: H =B1.49
6 C ∗ % ∗ ?
∗ *
: ,
Ditch A:
Q10 = 3.53 cfs – Q25 = 4.01 cfs – Q100 = 4.68 cfs (D4 + D6 Inlet Areas)
Trapezoidal–1’ bottom; 3:1 side slopes; 2.4’ depth; 0.30% slope; n=0.24; Qcap = 7.61 cfs
Capacity provided.
Ditch B:
Q10 = 1.71 cfs – Q25 = 1.94 cfs – Q100 = 2.26 cfs (D1 + D3 Inlet Areas)
Trapezoidal–2’ bottom; 2:1 side slopes; 2.5’ depth; 0.34% slope; n=0.24; Qcap = 7.63 cfs
Capacity provided.
Ditch C:
Q10 = 1.06 cfs – Q25 = 1.20 cfs – Q100 = 1.40 cfs (D3 Inlet Area)
Triangular – 0’ bottom; 2:1 side slopes; 1.4’ depth; 1.48% slope; n=0.24; Qcap = 2.16 cfs
Capacity provided.
Capacity was calculated using Hydraflow Express and results are presented in Appendix C.
Page | 22
Shear Stress
M(N *ℎ ( *E : Q/ = R/* ,#ℎ R = 62.4
5L
+E ,/ = / Eℎ,* = 5
Ditch A:
D10 = 1.77; Slope = 0.30%; Max Shear Stress = 0.33 lb/ft2
Velocity calculated as 0.32 ft/s.
Grass vegetation will suffice.
Ditch B:
D10 = 1.27’; Slope = 0.34%; Max Shear Stress = 0.27 lb/ft2
Velocity calculated as 0.30 ft/s.
Grass vegetation will suffice.
Ditch C:
D10 = 1.08’; Slope = 1.48%; Max Shear Stress = 1.00 lb/ft2
Velocity calculated as 0.45 ft/s.
Grass vegetation will suffice.
According to the NCDOT Guidelines for Drainage Studies and Hydraulic Design, Section 11.2,
driveway pipes should convey the same discharge as that for which the ditch is designed. These
requirements apply to the four (4) driveway crossing pipes. Capacity was also calculated for the
existing cross pipe that carries all conveyance across Barbados Blvd.
Driveway Pipe Calculations:
Capacity
M(66 6F< P. (E 6: H =B1.49
6 C ∗ % ∗ ?
∗ *
: ,
Pipe D5-D6 (Conveys Offsite Ditch):
Q10 = 1.37 cfs – Q25 = 1.56 cfs – Q100 = 1.82 cfs (D6 Inlet Area)
15” RCP; 0.23% slope; n=.013; Qcap = 3.10 cfs
Capacity provided.
Pipe D4-OA1 (Conveys Ditch A):
Q10 = 3.53 cfs – Q25 = 4.01 cfs – Q100 = 4.68 cfs (D4 + D6 Inlet Areas)
15” RCP; 0.32% slope; n=.013; Qcap = 3.65 cfs
Capacity provided.
Pipe D1-OA1 (Conveys Ditch B):
Q10 = 1.71 cfs – Q25 = 1.94 cfs – Q100 = 2.26 cfs (D1 + D3 Inlet Areas)
15” RCP; 0.31% slope; n=.013; Qcap = 3.60 cfs
Capacity provided.
Pipe D2-D3 (Conveys Ditch C):
Q10 = 1.06 cfs – Q25 = 1.20 cfs – Q100 = 1.40 cfs (D3 Inlet Area)
15” RCP; 0.32% slope; n=.013; Qcap = 3.65 cfs
Capacity provided.
Existing Pipe (Conveys Ditches & Pond Outfall)
Q10 = 9.31 cfs – Q25 = 10.64 cfs – Q100 = 16.96 cfs (D1 + D3 + D4 + D6 + Pond Outfall)
30” RCP; 0.36% slope; n=.013; Qcap = 24.61 cfs
Capacity provided.
Capacity was calculated using Hydraflow Express and results are presented in Appendix C.
Page | 23
VIII. MISCELLANEOUS CALCULATIONS
Buoyancy Narrative
Buoyancy calculations were completed to determine the anchoring requirements to prevent
flotation from the outlet structures, with a factor of safety of 1. 5 used.
Anti-Seep Narrative
The anti-seep collars shall be installed within the saturated zone and extend a minimum of 2 feet
around each of the outlet pipes. Connection between the collars and the outlet pipes shall be
watertight and not be closer than 2 feet to a pipe joint.
APPENDIX A
Parcel Map
The information made available by this service originates from the county'sbuilding permitting and inspections records. This GIS rendering is refreshed
on a monthly basis., New Hanover County NC, New Hanover County, NC
Property Owners
Addresses
Roads
Major Roads
Municipal Boundaries
Parcel Boundaries
5/1/2025, 4:05:35 PM
0 0.07 0.130.03 mi
0 0.1 0.20.05 km
1:4,000
NHC GIS Services
New Hanover County, NC
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National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOODHAZARD AREAS
Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or Depth Zone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone X
Future Conditions 1% Annual
Chance Flood Hazard Zone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood Hazard Zone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards
The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 5/1/2025 at 2:13 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
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unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location.
1:6,000
77°53'7"W 34°21'27"N
77°52'29"W 34°20'58"N
Basemap Imagery Source: USGS National Map 2023
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2026
Page 1 of 4
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234780 234850 234920 234990 235060 235130 235200
234780 234850 234920 234990 235060 235130 235200
34° 21' 17'' N
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84
0 100 200 400 600
Feet
0 40 80 160 240
Meters
Map Scale: 1:2,890 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:15,800.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: New Hanover County, North Carolina
Survey Area Data: Version 27, Aug 27, 2025
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Nov 8, 2022—Dec 1,
2022
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2026
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
Be Baymeade fine sand, 1
to 6 percent slopes
A 3.0 7.7%
DO Dorovan soils B/D 0.1 0.3%
Kr Kureb sand, 1 to 8
percent slopes
A 13.4 34.4%
Le Leon sand A/D 13.2 33.9%
Ly Lynn Haven fine sand A/D 4.3 11.0%
Mu Murville fine sand A/D 0.6 1.4%
Se Seagate fine sand B 4.4 11.3%
W Water 0.0 0.0%
Totals for Area of Interest 39.0 100.0%
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2026
Page 3 of 4
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2026
Page 4 of 4
NOAA Atlas 14, Volume 2, Version 3
Location name: Castle Hayne, North Carolina,
USA*
Latitude: 34.3524°, Longitude: -77.8814°
Elevation: 26 ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 0.518
(0.483‑0.559)
0.616
(0.573‑0.664)
0.720
(0.669‑0.776)
0.801
(0.742‑0.863)
0.905
(0.834‑0.972)
0.982
(0.901‑1.06)
1.06
(0.969‑1.14)
1.14
(1.03‑1.23)
1.24
(1.12‑1.34)
1.33
(1.18‑1.44)
10-min 0.827
(0.771‑0.893)
0.985
(0.916‑1.06)
1.15
(1.07‑1.24)
1.28
(1.19‑1.38)
1.44
(1.33‑1.55)
1.56
(1.44‑1.68)
1.69
(1.54‑1.82)
1.81
(1.64‑1.95)
1.97
(1.77‑2.13)
2.10
(1.86‑2.26)
15-min 1.03
(0.963‑1.12)
1.24
(1.15‑1.34)
1.46
(1.35‑1.57)
1.62
(1.50‑1.75)
1.83
(1.68‑1.96)
1.98
(1.82‑2.13)
2.13
(1.95‑2.30)
2.28
(2.07‑2.46)
2.48
(2.22‑2.68)
2.63
(2.34‑2.84)
30-min 1.42
(1.32‑1.53)
1.71
(1.59‑1.84)
2.07
(1.92‑2.23)
2.35
(2.18‑2.53)
2.71
(2.49‑2.91)
2.98
(2.74‑3.21)
3.27
(2.98‑3.52)
3.55
(3.22‑3.83)
3.95
(3.54‑4.26)
4.26
(3.79‑4.60)
60-min 1.77
(1.65‑1.91)
2.14
(2.00‑2.31)
2.66
(2.47‑2.86)
3.06
(2.83‑3.29)
3.60
(3.32‑3.87)
4.04
(3.71‑4.35)
4.50
(4.10‑4.84)
4.98
(4.52‑5.37)
5.66
(5.08‑6.11)
6.22
(5.53‑6.72)
2-hr 2.10
(1.94‑2.29)
2.56
(2.36‑2.80)
3.26
(3.00‑3.56)
3.84
(3.53‑4.19)
4.68
(4.27‑5.10)
5.40
(4.91‑5.88)
6.19
(5.59‑6.73)
7.05
(6.32‑7.66)
8.32
(7.37‑9.06)
9.41
(8.28‑10.3)
3-hr 2.25
(2.07‑2.46)
2.74
(2.52‑3.00)
3.50
(3.22‑3.83)
4.16
(3.80‑4.55)
5.14
(4.67‑5.60)
5.99
(5.42‑6.54)
6.94
(6.23‑7.57)
8.00
(7.12‑8.70)
9.61
(8.45‑10.5)
11.0
(9.57‑12.0)
6-hr 2.78
(2.56‑3.06)
3.39
(3.12‑3.72)
4.34
(3.98‑4.76)
5.16
(4.72‑5.66)
6.40
(5.81‑6.99)
7.48
(6.75‑8.17)
8.70
(7.80‑9.48)
10.1
(8.91‑11.0)
12.2
(10.6‑13.2)
14.0
(12.1‑15.3)
12-hr 3.26
(2.97‑3.61)
3.97
(3.62‑4.39)
5.12
(4.66‑5.66)
6.12
(5.55‑6.75)
7.64
(6.87‑8.41)
8.99
(8.04‑9.87)
10.5
(9.32‑11.5)
12.3
(10.7‑13.4)
14.9
(12.9‑16.4)
17.3
(14.7‑19.0)
24-hr 3.81
(3.45‑4.27)
4.62
(4.19‑5.19)
5.98
(5.41‑6.70)
7.17
(6.47‑8.02)
9.00
(8.03‑10.1)
10.6
(9.41‑11.9)
12.5
(10.9‑14.0)
14.6
(12.6‑16.3)
17.9
(15.1‑20.1)
20.8
(17.2‑23.5)
2-day 4.50
(4.09‑5.02)
5.44
(4.95‑6.07)
6.97
(6.33‑7.78)
8.31
(7.52‑9.27)
10.4
(9.28‑11.6)
12.1
(10.8‑13.6)
14.2
(12.4‑15.9)
16.5
(14.2‑18.5)
20.0
(16.9‑22.6)
23.0
(19.2‑26.2)
3-day 4.80
(4.37‑5.35)
5.79
(5.27‑6.46)
7.38
(6.70‑8.23)
8.75
(7.91‑9.75)
10.8
(9.69‑12.1)
12.6
(11.2‑14.1)
14.6
(12.9‑16.4)
16.9
(14.7‑19.0)
20.3
(17.3‑23.0)
23.3
(19.5‑26.5)
4-day 5.10
(4.64‑5.68)
6.15
(5.60‑6.86)
7.79
(7.07‑8.68)
9.19
(8.31‑10.2)
11.3
(10.1‑12.6)
13.1
(11.6‑14.6)
15.1
(13.3‑16.9)
17.3
(15.1‑19.4)
20.7
(17.7‑23.4)
23.6
(19.8‑26.8)
7-day 5.88
(5.41‑6.47)
7.09
(6.52‑7.80)
8.92
(8.18‑9.80)
10.4
(9.54‑11.5)
12.7
(11.5‑13.9)
14.6
(13.1‑16.0)
16.6
(14.8‑18.3)
18.9
(16.7‑20.8)
22.1
(19.2‑24.7)
24.9
(21.3‑27.9)
10-day 6.65
(6.12‑7.27)
7.96
(7.33‑8.72)
9.86
(9.07‑10.8)
11.5
(10.5‑12.5)
13.8
(12.6‑15.1)
15.7
(14.2‑17.2)
17.8
(16.0‑19.5)
20.1
(17.9‑22.1)
23.4
(20.5‑25.9)
26.1
(22.6‑29.2)
20-day 8.92
(8.28‑9.66)
10.6
(9.87‑11.5)
12.9
(12.0‑14.0)
14.9
(13.8‑16.1)
17.6
(16.2‑19.0)
19.9
(18.2‑21.5)
22.3
(20.2‑24.2)
24.8
(22.4‑27.1)
28.4
(25.3‑31.2)
31.4
(27.6‑34.7)
30-day 10.9
(10.3‑11.7)
13.0
(12.2‑14.0)
15.6
(14.6‑16.7)
17.7
(16.6‑19.0)
20.7
(19.2‑22.1)
23.0
(21.3‑24.7)
25.5
(23.4‑27.4)
28.0
(25.6‑30.2)
31.4
(28.4‑34.2)
34.2
(30.6‑37.3)
45-day 13.7
(12.9‑14.6)
16.2
(15.2‑17.2)
19.2
(18.0‑20.4)
21.6
(20.3‑23.0)
25.0
(23.4‑26.6)
27.6
(25.7‑29.5)
30.4
(28.1‑32.5)
33.2
(30.6‑35.7)
37.1
(33.7‑40.0)
40.1
(36.2‑43.6)
60-day 16.4
(15.5‑17.4)
19.3
(18.2‑20.6)
22.6
(21.3‑24.0)
25.2
(23.8‑26.8)
28.7
(27.0‑30.6)
31.5
(29.5‑33.5)
34.2
(31.9‑36.5)
37.0
(34.2‑39.6)
40.6
(37.3‑43.7)
43.4
(39.6‑47.0)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequencyestimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimatesat upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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Large scale aerial
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1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions@noaa.gov
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NOAA Atlas 14, Volume 2, Version 3
Location name: Castle Hayne, North Carolina,
USA*
Latitude: 34.3524°, Longitude: -77.8814°
Elevation: 26 ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1
Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 6.22
(5.80‑6.71)
7.39
(6.88‑7.97)
8.64
(8.03‑9.31)
9.61
(8.90‑10.4)
10.9
(10.0‑11.7)
11.8
(10.8‑12.7)
12.7
(11.6‑13.7)
13.7
(12.4‑14.7)
14.9
(13.4‑16.1)
16.0
(14.2‑17.3)
10-min 4.96
(4.63‑5.36)
5.91
(5.50‑6.37)
6.92
(6.43‑7.45)
7.69
(7.12‑8.28)
8.65
(7.97‑9.29)
9.39
(8.61‑10.1)
10.1
(9.23‑10.9)
10.9
(9.83‑11.7)
11.8
(10.6‑12.8)
12.6
(11.2‑13.6)
15-min 4.14
(3.85‑4.46)
4.95
(4.60‑5.34)
5.83
(5.42‑6.28)
6.48
(6.00‑6.98)
7.31
(6.74‑7.86)
7.92
(7.26‑8.52)
8.53
(7.78‑9.18)
9.13
(8.27‑9.83)
9.92
(8.90‑10.7)
10.5
(9.35‑11.4)
30-min 2.84
(2.64‑3.06)
3.42
(3.18‑3.69)
4.14
(3.85‑4.46)
4.70
(4.35‑5.06)
5.41
(4.99‑5.82)
5.97
(5.47‑6.42)
6.54
(5.96‑7.03)
7.11
(6.44‑7.65)
7.89
(7.08‑8.52)
8.52
(7.57‑9.21)
60-min 1.77
(1.65‑1.91)
2.14
(2.00‑2.31)
2.66
(2.47‑2.86)
3.06
(2.83‑3.29)
3.60
(3.32‑3.87)
4.04
(3.71‑4.35)
4.50
(4.10‑4.84)
4.98
(4.52‑5.37)
5.66
(5.08‑6.11)
6.22
(5.53‑6.72)
2-hr 1.05
(0.967‑1.15)
1.28
(1.18‑1.40)
1.63
(1.50‑1.78)
1.92
(1.76‑2.10)
2.34
(2.14‑2.55)
2.70
(2.45‑2.94)
3.09
(2.79‑3.37)
3.52
(3.16‑3.83)
4.16
(3.69‑4.53)
4.70
(4.14‑5.14)
3-hr 0.748
(0.690‑0.820)
0.911
(0.839‑0.999)
1.17
(1.07‑1.28)
1.38
(1.27‑1.52)
1.71
(1.56‑1.87)
2.00
(1.80‑2.18)
2.31
(2.07‑2.52)
2.66
(2.37‑2.90)
3.20
(2.81‑3.48)
3.67
(3.19‑4.00)
6-hr 0.464
(0.427‑0.510)
0.565
(0.521‑0.621)
0.724
(0.665‑0.795)
0.862
(0.788‑0.944)
1.07
(0.970‑1.17)
1.25
(1.13‑1.36)
1.45
(1.30‑1.58)
1.68
(1.49‑1.83)
2.03
(1.77‑2.21)
2.34
(2.02‑2.55)
12-hr 0.270
(0.246‑0.299)
0.329
(0.300‑0.364)
0.424
(0.386‑0.469)
0.508
(0.460‑0.560)
0.634
(0.570‑0.697)
0.746
(0.666‑0.819)
0.873
(0.773‑0.958)
1.02
(0.891‑1.12)
1.24
(1.07‑1.36)
1.44
(1.22‑1.58)
24-hr 0.158
(0.143‑0.177)
0.192
(0.174‑0.216)
0.248
(0.225‑0.279)
0.298
(0.269‑0.334)
0.375
(0.334‑0.419)
0.443
(0.392‑0.495)
0.520
(0.455‑0.582)
0.608
(0.524‑0.680)
0.744
(0.628‑0.838)
0.865
(0.717‑0.978)
2-day 0.093
(0.085‑0.104)
0.113
(0.103‑0.126)
0.145
(0.131‑0.162)
0.173
(0.156‑0.193)
0.215
(0.193‑0.240)
0.253
(0.224‑0.283)
0.295
(0.258‑0.330)
0.342
(0.296‑0.386)
0.416
(0.352‑0.470)
0.480
(0.399‑0.546)
3-day 0.066
(0.060‑0.074)
0.080
(0.073‑0.089)
0.102
(0.093‑0.114)
0.121
(0.109‑0.135)
0.150
(0.134‑0.167)
0.175
(0.155‑0.195)
0.203
(0.178‑0.227)
0.234
(0.203‑0.263)
0.282
(0.240‑0.319)
0.323
(0.271‑0.368)
4-day 0.053
(0.048‑0.059)
0.064
(0.058‑0.071)
0.081
(0.073‑0.090)
0.095
(0.086‑0.106)
0.117
(0.105‑0.130)
0.136
(0.121‑0.152)
0.157
(0.138‑0.175)
0.180
(0.156‑0.202)
0.215
(0.184‑0.243)
0.245
(0.206‑0.279)
7-day 0.035
(0.032‑0.038)
0.042
(0.038‑0.046)
0.053
(0.048‑0.058)
0.062
(0.056‑0.068)
0.075
(0.068‑0.082)
0.086
(0.078‑0.095)
0.098
(0.088‑0.109)
0.112
(0.099‑0.123)
0.131
(0.114‑0.146)
0.148
(0.126‑0.166)
10-day 0.027
(0.025‑0.030)
0.033
(0.030‑0.036)
0.041
(0.037‑0.045)
0.047
(0.043‑0.052)
0.057
(0.052‑0.062)
0.065
(0.059‑0.071)
0.074
(0.066‑0.081)
0.083
(0.074‑0.092)
0.097
(0.085‑0.108)
0.108
(0.094‑0.121)
20-day 0.018
(0.017‑0.020)
0.022
(0.020‑0.023)
0.026
(0.025‑0.029)
0.030
(0.028‑0.033)
0.036
(0.033‑0.039)
0.041
(0.037‑0.044)
0.046
(0.042‑0.050)
0.051
(0.046‑0.056)
0.059
(0.052‑0.065)
0.065
(0.057‑0.072)
30-day 0.015
(0.014‑0.016)
0.018
(0.016‑0.019)
0.021
(0.020‑0.023)
0.024
(0.023‑0.026)
0.028
(0.026‑0.030)
0.031
(0.029‑0.034)
0.035
(0.032‑0.037)
0.038
(0.035‑0.041)
0.043
(0.039‑0.047)
0.047
(0.042‑0.051)
45-day 0.012
(0.011‑0.013)
0.014
(0.014‑0.015)
0.017
(0.016‑0.018)
0.020
(0.018‑0.021)
0.023
(0.021‑0.024)
0.025
(0.023‑0.027)
0.028
(0.026‑0.030)
0.030
(0.028‑0.033)
0.034
(0.031‑0.037)
0.037
(0.033‑0.040)
60-day 0.011
(0.010‑0.012)
0.013
(0.012‑0.014)
0.015
(0.014‑0.016)
0.017
(0.016‑0.018)
0.019
(0.018‑0.021)
0.021
(0.020‑0.023)
0.023
(0.022‑0.025)
0.025
(0.023‑0.027)
0.028
(0.025‑0.030)
0.030
(0.027‑0.032)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (fora given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are notchecked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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National Weather Service
National Water Center
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions@noaa.gov
Disclaimer
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APPENDIX B
·
·
·
·
·
·
·
·
·
·
·
20
,
0
0
0
G
A
L
DS
L
7,0
0
0
G
A
L
DE
F
20
,
0
0
0
G
A
L
DS
L12
,
0
0
0
G
A
L
DS
L
PU
L
8,0
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Hydraflow Table of Contents 7-11CastleHayneNC_Hydraflow.gpw
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Watershed Model Schematic...................................................................................... 1
2 - Year
Summary Report......................................................................................................................... 2
Hydrograph Reports................................................................................................................... 3
Hydrograph No. 1, SCS Runoff, Pre-Dev Area 1..................................................................... 3
Hydrograph No. 2, SCS Runoff, Pre-Dev Area 2..................................................................... 4
Hydrograph No. 3, SCS Runoff, Pre-Dev Area 3..................................................................... 5
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A.................................................................. 6
Hydrograph No. 6, Reservoir, POND A.................................................................................... 7
Pond Report - POND A........................................................................................................ 8
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B............................................................... 10
Hydrograph No. 8, Combine, Post-Dev Area 1...................................................................... 11
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................. 12
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3................................................................ 13
10 - Year
Summary Report....................................................................................................................... 14
Hydrograph Reports................................................................................................................. 15
Hydrograph No. 1, SCS Runoff, Pre-Dev Area 1................................................................... 15
Hydrograph No. 2, SCS Runoff, Pre-Dev Area 2................................................................... 16
Hydrograph No. 3, SCS Runoff, Pre-Dev Area 3................................................................... 17
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A................................................................ 18
Hydrograph No. 6, Reservoir, POND A.................................................................................. 19
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B............................................................... 20
Hydrograph No. 8, Combine, Post-Dev Area 1...................................................................... 21
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................. 22
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3................................................................ 23
25 - Year
Summary Report....................................................................................................................... 24
Hydrograph Reports................................................................................................................. 25
Hydrograph No. 1, SCS Runoff, Pre-Dev Area 1................................................................... 25
Hydrograph No. 2, SCS Runoff, Pre-Dev Area 2................................................................... 26
Hydrograph No. 3, SCS Runoff, Pre-Dev Area 3................................................................... 27
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A................................................................ 28
Hydrograph No. 6, Reservoir, POND A.................................................................................. 29
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B............................................................... 30
Hydrograph No. 8, Combine, Post-Dev Area 1...................................................................... 31
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................. 32
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3................................................................ 33
100 - Year
Summary Report....................................................................................................................... 34
Hydrograph Reports................................................................................................................. 35
Hydrograph No. 1, SCS Runoff, Pre-Dev Area 1................................................................... 35
Hydrograph No. 2, SCS Runoff, Pre-Dev Area 2................................................................... 36
Hydrograph No. 3, SCS Runoff, Pre-Dev Area 3................................................................... 37
Contents continued...7-11CastleHayneNC_Hydraflow.gpw
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A................................................................ 38
Hydrograph No. 6, Reservoir, POND A.................................................................................. 39
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B............................................................... 40
Hydrograph No. 8, Combine, Post-Dev Area 1...................................................................... 41
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................. 42
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3................................................................ 43
IDF Report.................................................................................................................. 44
1 2 3 5
6
7
8
9 10
1
Watershed Model Schematic Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Project: 7-11CastleHayneNC_Hydraflow.gpw Wednesday, 02 / 25 / 2026
Hyd.Origin Description
Legend
1 SCS Runoff Pre-Dev Area 1
2 SCS Runoff Pre-Dev Area 2
3 SCS Runoff Pre-Dev Area 3
5 SCS Runoff Post-Dev Area 1A
6 Reservoir POND A
7 SCS Runoff Post-Dev Area 1B
8 Combine Post-Dev Area 1
9 SCS Runoff Post-Dev Area 2
10 SCS Runoff Post-Dev Area 3
Hydrograph Summary Report
2
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 0.572 2 756 5,844 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.000 2 n/a 0 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.004 2 892 97 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 10.60 2 728 40,730 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 0.535 2 928 37,515 5 24.02 27,750 POND A
7 SCS Runoff 0.446 2 734 2,051 ------ ------ ------ Post-Dev Area 1B
8 Combine 0.572 2 914 39,565 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.002 2 872 62 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.004 2 872 102 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow.gpw Return Period: 2 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 1
Pre-Dev Area 1
Hydrograph type = SCS Runoff Peak discharge = 0.572 cfs
Storm frequency = 2 yrs Time to peak = 12.60 hrs
Time interval = 2 min Hyd. volume = 5,844 cuft
Drainage area = 3.930 ac Curve number = 47
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 27.50 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
3
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Pre-Dev Area 1
Hyd. No. 1 -- 2 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 2
Pre-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.000 cfs
Storm frequency = 2 yrs Time to peak = n/a
Time interval = 2 min Hyd. volume = 0 cuft
Drainage area = 0.260 ac Curve number = 30
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 12.50 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
4
0.0 0.3 0.7 1.0 1.3 1.7 2.0
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Pre-Dev Area 2
Hyd. No. 2 -- 2 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 3
Pre-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.004 cfs
Storm frequency = 2 yrs Time to peak = 14.87 hrs
Time interval = 2 min Hyd. volume = 97 cuft
Drainage area = 0.250 ac Curve number = 38
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 10.40 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
5
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Pre-Dev Area 3
Hyd. No. 3 -- 2 Year
Hyd No. 3
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 10.60 cfs
Storm frequency = 2 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 40,730 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Post-Dev Area 1A
Hyd. No. 5 -- 2 Year
Hyd No. 5
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 0.535 cfs
Storm frequency = 2 yrs Time to peak = 15.47 hrs
Time interval = 2 min Hyd. volume = 37,515 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 24.02 ft
Reservoir name = POND A Max. Storage = 27,750 cuft
Storage Indication method used.
7
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
POND A
Hyd. No. 6 -- 2 Year
Hyd No. 6 Hyd No. 5 Total storage used = 27,750 cuft
Pond Report 8
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Pond No. 1 - POND A
Pond Data
Contours -User-defined contour areas. Average end area method used for volume calculation. Begining Elevation = 22.50 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 22.50 15,874 0 0
0.50 23.00 16,447 8,080 8,080
1.50 24.00 21,910 19,178 27,258
2.50 25.00 24,565 23,237 50,496
3.50 26.00 27,321 25,943 76,439
4.00 26.50 28,816 14,034 90,473
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr] [A] [B] [C] [D]
Rise (in)= 15.00 2.00 Inactive 0.00
Span (in)= 15.00 2.00 0.00 0.00
No. Barrels = 1 1 1 0
Invert El. (ft)= 22.50 22.50 0.00 0.00
Length (ft)= 105.00 0.00 0.00 0.00
Slope (%)= 0.14 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a Yes Yes No
Crest Len (ft)= 18.67 0.33 1.33 75.00
Crest El. (ft)= 25.00 23.50 24.05 25.58
Weir Coeff.= 3.33 3.33 3.33 2.60
Weir Type = 1 Rect Rect Broad
Multi-Stage = Yes Yes Yes No
Exfil.(in/hr)= 0.000 (by Contour)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Storage / Discharge Table
Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
0.00 0 22.50 0.00 0.00 --- --- 0.00 0.00 0.00 0.00 --- --- 0.000
0.05 808 22.55 0.00 oc 0.00 ic --- --- 0.00 0.00 0.00 0.00 ------ 0.003
0.10 1,616 22.60 0.01 oc 0.01 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.013
0.15 2,424 22.65 0.03 oc 0.03 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.025
0.20 3,232 22.70 0.04 oc 0.03 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.033
0.25 4,040 22.75 0.04 oc 0.04 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.040
0.30 4,848 22.80 0.05 oc 0.04 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.045
0.35 5,656 22.85 0.05 oc 0.05 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.050
0.40 6,464 22.90 0.06 oc 0.05 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.054
0.45 7,272 22.95 0.06 oc 0.06 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.059
0.50 8,080 23.00 0.06 oc 0.06 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.063
0.60 9,998 23.10 0.08 oc 0.07 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.070
0.70 11,916 23.20 0.08 oc 0.08 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.077
0.80 13,834 23.30 0.09 oc 0.08 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.084
0.90 15,751 23.40 0.10 oc 0.09 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.090
1.00 17,669 23.50 0.10 oc 0.10 ic --- --- 0.00 0.00 0.00 0.00 --- --- 0.096
1.10 19,587 23.60 0.14 oc 0.10 ic --- --- 0.00 0.03 0.00 0.00 --- --- 0.134
1.20 21,505 23.70 0.20 oc 0.10 ic --- --- 0.00 0.10 0.00 0.00 --- --- 0.201
1.30 23,423 23.80 0.30 oc 0.10 ic --- --- 0.00 0.18 0.00 0.00 --- --- 0.285
1.40 25,341 23.90 0.39 oc 0.11 ic --- --- 0.00 0.28 0.00 0.00 --- --- 0.385
1.50 27,258 24.00 0.50 oc 0.11 ic --- --- 0.00 0.39 0.00 0.00 --- --- 0.498
1.60 29,582 24.10 0.68 oc 0.11 ic --- --- 0.00 0.51 0.05 0.00 --- --- 0.670
1.70 31,906 24.20 1.02 oc 0.11 ic --- --- 0.00 0.64 0.26 0.00 --- --- 1.009
1.80 34,230 24.30 1.46 oc 0.10 ic --- --- 0.00 0.79 0.55 0.00 --- --- 1.443
1.90 36,553 24.40 1.93 oc 0.09 ic --- --- 0.00 0.92 s 0.92 0.00 --- --- 1.931
2.00 38,877 24.50 2.43 oc 0.09 ic --- --- 0.00 1.01 s 1.34 0.00 --- --- 2.431
2.10 41,201 24.60 3.01 oc 0.08 ic --- --- 0.00 1.12 s 1.81 0.00 --- --- 3.008
2.20 43,525 24.70 3.58 oc 0.08 ic --- --- 0.00 1.21 s 2.29 s 0.00 --- --- 3.577
2.30 45,848 24.80 4.06 oc 0.08 ic --- --- 0.00 1.29 s 2.69 s 0.00 --- --- 4.059
2.40 48,172 24.90 4.49 oc 0.07 ic --- --- 0.00 1.36 s 3.05 s 0.00 --- --- 4.487
2.50 50,496 25.00 4.87 oc 0.07 ic --- --- 0.00 1.42 s 3.38 s 0.00 --- --- 4.872
2.60 53,090 25.10 5.75 oc 0.04 ic --- --- 1.97 1.07 s 2.67 s 0.00 --- --- 5.747
2.70 55,684 25.20 6.20 oc 0.02 ic --- --- 3.61 s 0.71 s 1.85 s 0.00 --- --- 6.191
2.80 58,279 25.30 6.44 oc 0.02 ic --- --- 4.33 s 0.57 s 1.52 s 0.00 --- --- 6.433
2.90 60,873 25.40 6.65 oc 0.01 ic --- --- 4.81 s 0.48 s 1.33 s 0.00 --- --- 6.641
3.00 63,467 25.50 6.84 oc 0.01 ic --- --- 5.17 s 0.43 s 1.21 s 0.00 --- --- 6.817
3.10 66,062 25.60 7.02 oc 0.01 ic --- --- 5.46 s 0.39 s 1.12 s 0.55 --- --- 7.534
Continues on next page...
9
POND A
Stage / Storage / Discharge Table
Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
3.20 68,656 25.70 7.20 oc 0.01 ic --- --- 5.71 s 0.36 s 1.06 s 8.11 --- --- 15.24
3.30 71,250 25.80 7.37 oc 0.01 ic --- --- 5.97 s 0.34 s 1.02 s 20.12 --- --- 27.46
3.40 73,845 25.90 7.54 oc 0.00 ic --- --- 6.12 s 0.32 s 0.97 s 35.30 --- --- 42.72
3.50 76,439 26.00 7.70 oc 0.00 ic --- --- 6.37 s 0.31 s 0.96 s 53.08 --- --- 60.72
3.55 77,842 26.05 7.78 oc 0.00 ic --- --- 6.43 s 0.31 s 0.94 s 62.83 --- --- 70.51
3.60 79,246 26.10 7.86 oc 0.00 ic --- --- 6.61 s 0.30 s 0.94 s 73.12 --- --- 80.98
3.65 80,649 26.15 7.94 oc 0.00 ic --- --- 6.57 s 0.29 s 0.92 s 83.92 --- --- 91.70
3.70 82,053 26.20 8.02 oc 0.00 ic --- --- 6.68 s 0.29 s 0.91 s 95.20 --- --- 103.09
3.75 83,456 26.25 8.09 oc 0.00 ic --- --- 6.76 s 0.29 s 0.90 s 106.94 --- --- 114.90
3.80 84,859 26.30 8.17 oc 0.00 ic --- --- 6.81 s 0.28 s 0.89 s 119.13 --- --- 127.13
3.85 86,263 26.35 8.24 oc 0.00 ic --- --- 6.80 s 0.28 s 0.88 s 131.75 --- --- 139.71
3.90 87,666 26.40 8.32 oc 0.00 ic --- --- 7.08 s 0.28 s 0.90 s 144.79 --- --- 153.06
3.95 89,070 26.45 8.39 oc 0.00 ic --- --- 7.03 s 0.27 s 0.88 s 158.24 --- --- 166.43
4.00 90,473 26.50 8.47 oc 0.00 ic --- --- 6.98 s 0.27 s 0.86 s 172.07 --- --- 180.18
...End
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 0.446 cfs
Storm frequency = 2 yrs Time to peak = 12.23 hrs
Time interval = 2 min Hyd. volume = 2,051 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
10
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Post-Dev Area 1B
Hyd. No. 7 -- 2 Year
Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 0.572 cfs
Storm frequency = 2 yrs Time to peak = 15.23 hrs
Time interval = 2 min Hyd. volume = 39,565 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
11
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Post-Dev Area 1
Hyd. No. 8 -- 2 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.002 cfs
Storm frequency = 2 yrs Time to peak = 14.53 hrs
Time interval = 2 min Hyd. volume = 62 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
12
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Post-Dev Area 2
Hyd. No. 9 -- 2 Year
Hyd No. 9
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.004 cfs
Storm frequency = 2 yrs Time to peak = 14.53 hrs
Time interval = 2 min Hyd. volume = 102 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 4.62 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
13
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Post-Dev Area 3
Hyd. No. 10 -- 2 Year
Hyd No. 10
Hydrograph Summary Report
14
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 3.406 2 746 21,282 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.009 2 824 236 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.098 2 738 706 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 18.87 2 728 73,828 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 3.040 2 764 70,362 5 24.61 41,331 POND A
7 SCS Runoff 1.018 2 734 4,508 ------ ------ ------ Post-Dev Area 1B
8 Combine 3.394 2 756 74,870 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.069 2 726 395 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.113 2 726 650 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow.gpw Return Period: 10 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 1
Pre-Dev Area 1
Hydrograph type = SCS Runoff Peak discharge = 3.406 cfs
Storm frequency = 10 yrs Time to peak = 12.43 hrs
Time interval = 2 min Hyd. volume = 21,282 cuft
Drainage area = 3.930 ac Curve number = 47
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 27.50 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
15
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (hrs)
Pre-Dev Area 1
Hyd. No. 1 -- 10 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 2
Pre-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.009 cfs
Storm frequency = 10 yrs Time to peak = 13.73 hrs
Time interval = 2 min Hyd. volume = 236 cuft
Drainage area = 0.260 ac Curve number = 30
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 12.50 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
16
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Pre-Dev Area 2
Hyd. No. 2 -- 10 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 3
Pre-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.098 cfs
Storm frequency = 10 yrs Time to peak = 12.30 hrs
Time interval = 2 min Hyd. volume = 706 cuft
Drainage area = 0.250 ac Curve number = 38
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 10.40 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
17
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Pre-Dev Area 3
Hyd. No. 3 -- 10 Year
Hyd No. 3
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 18.87 cfs
Storm frequency = 10 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 73,828 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
18
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
3.00 3.00
6.00 6.00
9.00 9.00
12.00 12.00
15.00 15.00
18.00 18.00
21.00 21.00
Q (cfs)
Time (hrs)
Post-Dev Area 1A
Hyd. No. 5 -- 10 Year
Hyd No. 5
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 3.040 cfs
Storm frequency = 10 yrs Time to peak = 12.73 hrs
Time interval = 2 min Hyd. volume = 70,362 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 24.61 ft
Reservoir name = POND A Max. Storage = 41,331 cuft
Storage Indication method used.
19
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
3.00 3.00
6.00 6.00
9.00 9.00
12.00 12.00
15.00 15.00
18.00 18.00
21.00 21.00
Q (cfs)
Time (hrs)
POND A
Hyd. No. 6 -- 10 Year
Hyd No. 6 Hyd No. 5 Total storage used = 41,331 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 1.018 cfs
Storm frequency = 10 yrs Time to peak = 12.23 hrs
Time interval = 2 min Hyd. volume = 4,508 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
20
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (hrs)
Post-Dev Area 1B
Hyd. No. 7 -- 10 Year
Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 3.394 cfs
Storm frequency = 10 yrs Time to peak = 12.60 hrs
Time interval = 2 min Hyd. volume = 74,870 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
21
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (hrs)
Post-Dev Area 1
Hyd. No. 8 -- 10 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.069 cfs
Storm frequency = 10 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 395 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
22
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Post-Dev Area 2
Hyd. No. 9 -- 10 Year
Hyd No. 9
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.113 cfs
Storm frequency = 10 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 650 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 7.17 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
23
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Post-Dev Area 3
Hyd. No. 10 -- 10 Year
Hyd No. 10
Hydrograph Summary Report
24
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 6.307 2 744 36,011 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.071 2 744 660 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.267 2 732 1,397 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 24.80 2 728 98,301 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 5.557 2 756 94,742 5 25.08 52,526 POND A
7 SCS Runoff 1.463 2 734 6,464 ------ ------ ------ Post-Dev Area 1B
8 Combine 6.201 2 752 101,207 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.193 2 726 764 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.316 2 726 1,254 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow.gpw Return Period: 25 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 1
Pre-Dev Area 1
Hydrograph type = SCS Runoff Peak discharge = 6.307 cfs
Storm frequency = 25 yrs Time to peak = 12.40 hrs
Time interval = 2 min Hyd. volume = 36,011 cuft
Drainage area = 3.930 ac Curve number = 47
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 27.50 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
25
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (hrs)
Pre-Dev Area 1
Hyd. No. 1 -- 25 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 2
Pre-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.071 cfs
Storm frequency = 25 yrs Time to peak = 12.40 hrs
Time interval = 2 min Hyd. volume = 660 cuft
Drainage area = 0.260 ac Curve number = 30
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 12.50 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
26
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (hrs)
Pre-Dev Area 2
Hyd. No. 2 -- 25 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 3
Pre-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.267 cfs
Storm frequency = 25 yrs Time to peak = 12.20 hrs
Time interval = 2 min Hyd. volume = 1,397 cuft
Drainage area = 0.250 ac Curve number = 38
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 10.40 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
27
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Pre-Dev Area 3
Hyd. No. 3 -- 25 Year
Hyd No. 3
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 24.80 cfs
Storm frequency = 25 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 98,301 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
28
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (hrs)
Post-Dev Area 1A
Hyd. No. 5 -- 25 Year
Hyd No. 5
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 5.557 cfs
Storm frequency = 25 yrs Time to peak = 12.60 hrs
Time interval = 2 min Hyd. volume = 94,742 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 25.08 ft
Reservoir name = POND A Max. Storage = 52,526 cuft
Storage Indication method used.
29
0 8 16 24 32 40 48 56 64 72 80
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (hrs)
POND A
Hyd. No. 6 -- 25 Year
Hyd No. 6 Hyd No. 5 Total storage used = 52,526 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 1.463 cfs
Storm frequency = 25 yrs Time to peak = 12.23 hrs
Time interval = 2 min Hyd. volume = 6,464 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
30
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (hrs)
Post-Dev Area 1B
Hyd. No. 7 -- 25 Year
Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 6.201 cfs
Storm frequency = 25 yrs Time to peak = 12.53 hrs
Time interval = 2 min Hyd. volume = 101,207 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
31
0 8 16 24 32 40 48 56 64 72
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (hrs)
Post-Dev Area 1
Hyd. No. 8 -- 25 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.193 cfs
Storm frequency = 25 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 764 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
32
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Post-Dev Area 2
Hyd. No. 9 -- 25 Year
Hyd No. 9
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.316 cfs
Storm frequency = 25 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 1,254 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 9.00 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
33
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Post-Dev Area 3
Hyd. No. 10 -- 25 Year
Hyd No. 10
Hydrograph Summary Report
34
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 12.96 2 742 69,571 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.354 2 732 1,916 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.737 2 730 3,125 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 36.02 2 728 145,843 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 17.55 2 742 142,165 5 25.72 69,146 POND A
7 SCS Runoff 2.350 2 732 10,437 ------ ------ ------ Post-Dev Area 1B
8 Combine 19.46 2 742 152,601 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.513 2 724 1,673 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.843 2 724 2,748 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow.gpw Return Period: 100 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 1
Pre-Dev Area 1
Hydrograph type = SCS Runoff Peak discharge = 12.96 cfs
Storm frequency = 100 yrs Time to peak = 12.37 hrs
Time interval = 2 min Hyd. volume = 69,571 cuft
Drainage area = 3.930 ac Curve number = 47
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 27.50 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
35
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
14.00 14.00
Q (cfs)
Time (hrs)
Pre-Dev Area 1
Hyd. No. 1 -- 100 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 2
Pre-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.354 cfs
Storm frequency = 100 yrs Time to peak = 12.20 hrs
Time interval = 2 min Hyd. volume = 1,916 cuft
Drainage area = 0.260 ac Curve number = 30
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 12.50 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
36
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (hrs)
Pre-Dev Area 2
Hyd. No. 2 -- 100 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 3
Pre-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.737 cfs
Storm frequency = 100 yrs Time to peak = 12.17 hrs
Time interval = 2 min Hyd. volume = 3,125 cuft
Drainage area = 0.250 ac Curve number = 38
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 10.40 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
37
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Pre-Dev Area 3
Hyd. No. 3 -- 100 Year
Hyd No. 3
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 36.02 cfs
Storm frequency = 100 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 145,843 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
38
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
Q (cfs)
Time (hrs)
Post-Dev Area 1A
Hyd. No. 5 -- 100 Year
Hyd No. 5
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 17.55 cfs
Storm frequency = 100 yrs Time to peak = 12.37 hrs
Time interval = 2 min Hyd. volume = 142,165 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 25.72 ft
Reservoir name = POND A Max. Storage = 69,146 cuft
Storage Indication method used.
39
0 4 8 12 16 20 24 28 32
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
Q (cfs)
Time (hrs)
POND A
Hyd. No. 6 -- 100 Year
Hyd No. 6 Hyd No. 5 Total storage used = 69,146 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 2.350 cfs
Storm frequency = 100 yrs Time to peak = 12.20 hrs
Time interval = 2 min Hyd. volume = 10,437 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
40
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Q (cfs)
Time (hrs)
Post-Dev Area 1B
Hyd. No. 7 -- 100 Year
Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 19.46 cfs
Storm frequency = 100 yrs Time to peak = 12.37 hrs
Time interval = 2 min Hyd. volume = 152,601 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
41
0 4 8 12 16 20 24 28 32
Q (cfs)
0.00 0.00
3.00 3.00
6.00 6.00
9.00 9.00
12.00 12.00
15.00 15.00
18.00 18.00
21.00 21.00
Q (cfs)
Time (hrs)
Post-Dev Area 1
Hyd. No. 8 -- 100 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.513 cfs
Storm frequency = 100 yrs Time to peak = 12.07 hrs
Time interval = 2 min Hyd. volume = 1,673 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
42
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Post-Dev Area 2
Hyd. No. 9 -- 100 Year
Hyd No. 9
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.843 cfs
Storm frequency = 100 yrs Time to peak = 12.07 hrs
Time interval = 2 min Hyd. volume = 2,748 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
43
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Post-Dev Area 3
Hyd. No. 10 -- 100 Year
Hyd No. 10
Hydraflow Rainfall Report 44
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Return Intensity-Duration-Frequency Equation Coefficients (FHA)
Period
(Yrs) B D E (N/A)
1 79.7999 12.7000 0.8885 --------
2 96.4968 13.1000 0.8874 --------
3 0.0000 0.0000 0.0000 --------
5 92.4190 12.5000 0.8283 --------
10 94.9161 12.4000 0.8021 --------
25 84.4290 10.9000 0.7404 --------
50 79.3773 10.2000 0.7005 --------
100 74.4724 9.5000 0.6617 --------
File name: CastleHayne_IDF.IDF
Intensity = B / (Tc + D)^E
Return Intensity Values (in/hr)
Period
(Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60
1 6.21 4.98 4.17 3.60 3.17 2.84 2.57 2.36 2.17 2.02 1.89 1.77
2 7.39 5.95 5.00 4.32 3.82 3.42 3.10 2.84 2.62 2.44 2.28 2.14
3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
5 8.63 7.01 5.94 5.17 4.59 4.14 3.78 3.48 3.22 3.01 2.82 2.66
10 9.60 7.84 6.67 5.83 5.20 4.70 4.30 3.97 3.69 3.45 3.24 3.06
25 10.89 8.89 7.59 6.66 5.96 5.41 4.97 4.60 4.29 4.03 3.80 3.60
50 11.80 9.67 8.28 7.29 6.55 5.97 5.50 5.11 4.78 4.50 4.25 4.04
100 12.69 10.43 8.97 7.93 7.15 6.54 6.04 5.63 5.29 4.99 4.73 4.50
Tc = time in minutes. Values may exceed 60.
Rainfall Precipitation Table (in)
Precip. file name: H:\Developer\Crosland\7-11\Castle Hayne NC\Documents\SWM Design\Stormwater Model\CastleHayne_PCP.pcp
Storm
Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
SCS 24-hour 3.81 4.62 2.44 5.98 7.17 9.00 10.60 12.50
SCS 6-Hr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-1st 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Custom 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Hydraflow Table of Contents 7-11CastleHayneNC_Hydraflow.gpw
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Watershed Model Schematic...................................................................................... 1
3 - Year
Summary Report......................................................................................................................... 2
Hydrograph Reports................................................................................................................... 3
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A.................................................................. 3
Hydrograph No. 6, Reservoir, POND A.................................................................................... 4
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B................................................................. 5
Hydrograph No. 8, Combine, Post-Dev Area 1........................................................................ 6
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................... 7
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3.................................................................. 8
1.5" Water Quality Event
1 2 3 5
6
7
8
9 10
1
Watershed Model Schematic Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Project: 7-11CastleHayneNC_Hydraflow.gpw Wednesday, 02 / 25 / 2026
Hyd.Origin Description
Legend
1 SCS Runoff Pre-Dev Area 1
2 SCS Runoff Pre-Dev Area 2
3 SCS Runoff Pre-Dev Area 3
5 SCS Runoff Post-Dev Area 1A
6 Reservoir POND A
7 SCS Runoff Post-Dev Area 1B
8 Combine Post-Dev Area 1
9 SCS Runoff Post-Dev Area 2
10 SCS Runoff Post-Dev Area 3
Hydrograph Summary Report
2
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 0.003 2 1338 42 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.000 2 n/a 0 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.000 2 n/a 0 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 3.828 2 730 14,895 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 0.077 2 1342 13,618 5 23.19 11,754 POND A
7 SCS Runoff 0.074 2 742 460 ------ ------ ------ Post-Dev Area 1B
8 Combine 0.126 2 744 14,078 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.000 2 n/a 0 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.000 2 n/a 0 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow.gpw Return Period: 3 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
1.5" Water
Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 3.828 cfs
Storm frequency = 3 yrs Time to peak = 730 min
Time interval = 2 min Hyd. volume = 14,895 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 2.44 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
3
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (min)
Post-Dev Area 1A
Hyd. No. 5 -- 3 Year
Hyd No. 5
1.5" Water Quality Event
1.5" Water Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 0.077 cfs
Storm frequency = 3 yrs Time to peak = 1342 min
Time interval = 2 min Hyd. volume = 13,618 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 23.19 ft
Reservoir name = POND A Max. Storage = 11,754 cuft
Storage Indication method used.
4
0 600 1200 1800 2400 3000 3600 4200 4800 5400 6000
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (min)
POND A
Hyd. No. 6 -- 3 Year
Hyd No. 6 Hyd No. 5 Total storage used = 11,754 cuft
1.5" Water Quality Event
1.5" Water Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 0.074 cfs
Storm frequency = 3 yrs Time to peak = 742 min
Time interval = 2 min Hyd. volume = 460 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 2.44 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
5
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
Post-Dev Area 1B
Hyd. No. 7 -- 3 Year
Hyd No. 7
1.5" Water Quality Event
1.5" Water Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 0.126 cfs
Storm frequency = 3 yrs Time to peak = 744 min
Time interval = 2 min Hyd. volume = 14,078 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
6
0 600 1200 1800 2400 3000 3600 4200 4800 5400 6000
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
Post-Dev Area 1
Hyd. No. 8 -- 3 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
1.5" Water Quality Event
1.5" Water Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.000 cfs
Storm frequency = 3 yrs Time to peak = n/a
Time interval = 2 min Hyd. volume = 0 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 2.44 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
7
0 20 40 60 80 100 120
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
Post-Dev Area 2
Hyd. No. 9 -- 3 Year
Hyd No. 9
1.5" Water Quality Event
1.5" Water Quality Event
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.000 cfs
Storm frequency = 3 yrs Time to peak = n/a
Time interval = 2 min Hyd. volume = 0 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 2.44 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
8
0 20 40 60 80 100 120
Q (cfs)
0.00 0.00
0.01 0.01
0.02 0.02
0.03 0.03
0.04 0.04
0.05 0.05
0.06 0.06
0.07 0.07
0.08 0.08
0.09 0.09
0.10 0.10
Q (cfs)
Time (min)
Post-Dev Area 3
Hyd. No. 10 -- 3 Year
Hyd No. 10
1.5" Water Quality Event
1.5" Water Quality Event
Hydraflow Table of Contents 7-11CastleHayneNC_Hydraflow_Clogged.gpw
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Watershed Model Schematic...................................................................................... 1
100 - Year
Summary Report......................................................................................................................... 2
Hydrograph Reports................................................................................................................... 3
Hydrograph No. 5, SCS Runoff, Post-Dev Area 1A.................................................................. 3
Hydrograph No. 6, Reservoir, POND A.................................................................................... 4
Hydrograph No. 7, SCS Runoff, Post-Dev Area 1B................................................................. 5
Hydrograph No. 8, Combine, Post-Dev Area 1........................................................................ 6
Hydrograph No. 9, SCS Runoff, Post-Dev Area 2.................................................................... 7
Hydrograph No. 10, SCS Runoff, Post-Dev Area 3.................................................................. 8
Clogged Condition
1 2 3 5
6
7
8
9 10
1
Watershed Model Schematic Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
Project: 7-11CastleHayneNC_Hydraflow_Clogged.gpw Wednesday, 02 / 25 / 2026
Hyd.Origin Description
Legend
1 SCS Runoff Pre-Dev Area 1
2 SCS Runoff Pre-Dev Area 2
3 SCS Runoff Pre-Dev Area 3
5 SCS Runoff Post-Dev Area 1A
6 Reservoir POND A
7 SCS Runoff Post-Dev Area 1B
8 Combine Post-Dev Area 1
9 SCS Runoff Post-Dev Area 2
10 SCS Runoff Post-Dev Area 3
Hydrograph Summary Report
2
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 12.96 2 742 69,571 ------ ------ ------ Pre-Dev Area 1
2 SCS Runoff 0.354 2 732 1,916 ------ ------ ------ Pre-Dev Area 2
3 SCS Runoff 0.737 2 730 3,125 ------ ------ ------ Pre-Dev Area 3
5 SCS Runoff 36.02 2 728 145,843 ------ ------ ------ Post-Dev Area 1A
6 Reservoir 23.24 2 738 82,371 5 25.82 71,784 POND A
7 SCS Runoff 2.350 2 732 10,437 ------ ------ ------ Post-Dev Area 1B
8 Combine 25.41 2 738 92,807 6, 7 ------ ------ Post-Dev Area 1
9 SCS Runoff 0.513 2 724 1,673 ------ ------ ------ Post-Dev Area 2
10 SCS Runoff 0.843 2 724 2,748 ------ ------ ------ Post-Dev Area 3
7-11CastleHayneNC_Hydraflow_Clogged.gpwReturn Period: 100 Year Wednesday, 02 / 25 / 2026
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024
100 Year
Clogged Cond.
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 5
Post-Dev Area 1A
Hydrograph type = SCS Runoff Peak discharge = 36.02 cfs
Storm frequency = 100 yrs Time to peak = 728 min
Time interval = 2 min Hyd. volume = 145,843 cuft
Drainage area = 3.720 ac Curve number = 84
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 11.70 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
3
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
Q (cfs)
Time (min)
Post-Dev Area 1A
Hyd. No. 5 -- 100 Year
Hyd No. 5
Clogged Condition
Clogged Condition
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 6
POND A
Hydrograph type = Reservoir Peak discharge = 23.24 cfs
Storm frequency = 100 yrs Time to peak = 738 min
Time interval = 2 min Hyd. volume = 82,371 cuft
Inflow hyd. No. = 5 - Post-Dev Area 1A Max. Elevation = 25.82 ft
Reservoir name = POND A Max. Storage = 71,784 cuft
Storage Indication method used.
4
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
Q (cfs)
Time (min)
POND A
Hyd. No. 6 -- 100 Year
Hyd No. 6 Hyd No. 5 Total storage used = 71,784 cuft
Clogged Condition
Clogged Condition
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 7
Post-Dev Area 1B
Hydrograph type = SCS Runoff Peak discharge = 2.350 cfs
Storm frequency = 100 yrs Time to peak = 732 min
Time interval = 2 min Hyd. volume = 10,437 cuft
Drainage area = 0.350 ac Curve number = 68
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 16.80 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
5
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Q (cfs)
Time (min)
Post-Dev Area 1B
Hyd. No. 7 -- 100 Year
Hyd No. 7
Clogged Condition
Clogged Condition
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 8
Post-Dev Area 1
Hydrograph type = Combine Peak discharge = 25.41 cfs
Storm frequency = 100 yrs Time to peak = 738 min
Time interval = 2 min Hyd. volume = 92,807 cuft
Inflow hyds. = 6, 7 Contrib. drain. area = 0.350 ac
6
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
4.00 4.00
8.00 8.00
12.00 12.00
16.00 16.00
20.00 20.00
24.00 24.00
28.00 28.00
Q (cfs)
Time (min)
Post-Dev Area 1
Hyd. No. 8 -- 100 Year
Hyd No. 8 Hyd No. 6 Hyd No. 7
Clogged Condition
Clogged Condition
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 9
Post-Dev Area 2
Hydrograph type = SCS Runoff Peak discharge = 0.513 cfs
Storm frequency = 100 yrs Time to peak = 724 min
Time interval = 2 min Hyd. volume = 1,673 cuft
Drainage area = 0.140 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
7
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (min)
Post-Dev Area 2
Hyd. No. 9 -- 100 Year
Hyd No. 9
Clogged Condition
Clogged Condition
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2024 Wednesday, 02 / 25 / 2026
Hyd. No. 10
Post-Dev Area 3
Hydrograph type = SCS Runoff Peak discharge = 0.843 cfs
Storm frequency = 100 yrs Time to peak = 724 min
Time interval = 2 min Hyd. volume = 2,748 cuft
Drainage area = 0.230 ac Curve number = 39
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 12.50 in Distribution = Type III
Storm duration = 24 hrs Shape factor = 484
8
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (min)
Post-Dev Area 3
Hyd. No. 10 -- 100 Year
Hyd No. 10
Clogged Condition
Clogged Condition
APPENDIX C
20
,
0
0
0
G
A
L
DS
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7,0
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G
A
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G
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DS
L12
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PU
L
8,0
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G
A
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G
A
L
RU
L
F
F
F F
F
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·
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·
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·
20
,
0
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0
G
A
L
DS
L
7,0
0
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G
A
L
DE
F
20
,
0
0
0
G
A
L
DS
L12
,
0
0
0
G
A
L
DS
L
PU
L
8,0
0
0
G
A
L
20
,
0
0
0
G
A
L
RU
L
F
F
F F
F
·
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