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HomeMy WebLinkAboutNHC_Floodplain Program Technical Report_04_2025 New Hanover County Floodplain Program 2025 Prepared by Ken Vafier, 2025 New Hanover County Floodplain Program 1 Background, Purpose and Need of Floodplain Management Program In 1968, Congress authorized creation of the National Flood Insurance Program (NFIP) to reduce the impact of flooding in the United States by providing flood insurance, encouraging floodplain management, mapping flood hazards, and providing federal assistance when necessary to participating communities who agree to adopt and enforce floodplain management regulations and Flood Insurance Rate Maps (FIRMs). New Hanover County entered the NFIP in 1978 and continues to operate a floodplain management program consistent with the principles set forth in the NFIP. Article 9 of the county’s Unified Development Ordinance contains the applicable floodplain management regulations, and the county has updated FIRM’s that were largely updated in 2018, with some panels with neighboring jurisdictions that became effective in 2019 and 2025, respectively. The county’s direct proximity to multiple large water bodies necessitates a sound floodplain management program. Overview of Concerns and Types of Flooding The county has a unique geographic location directly on the Atlantic Coast and adjacent to the Cape Fear River with several watersheds characterized by tidal creeks which drain to either the ocean or river. The area largely consists of low-lying topography with significant wetland areas, thus much of the land area in New Hanover County is susceptible to flooding from a variety of sources during severe weather and significant rainfall events. Tropical cyclones and other coastal storms with potential for heavy rainfall can cause regular, rapid inundation of lower lying areas during these events. Larger events may also bring inundation via storm surge, and areas along the oceanfront, intracoastal waterway, and tidal creeks are susceptible to inundation, erosion, and damage from storm surge and increased wave action. Flooding may also be exacerbated during rainfall events in areas with poor local drainage, outdated or damaged stormwater infrastructure. Current Special Flood Hazard Area Designations As required through the County’s participation in the NFIP, Special Flood Hazard Areas (SFHAs) are delineated areas that have the potential to be inundated to the base flood elevation, defined as the water surface elevation that can be expected during a flood event having a1% or greater annual chance of occurring. The SFHA zones in New Hanover County include AE, AE floodway Coastal A, and VE. The flood zone designations are generally based on characteristics of flooding within and contain different regulations on development that must be adhered to. The AE flood zone encompasses the largest designation in the county and during a base flood event is expected to experience inundation to its prescribed water surface elevation, but damage from surge or wave action is less likely. As such, these areas are typically located slightly further from open water bodies but in low-lying areas where floodwater may extend to during periods of increased water levels. Examples include along the Cape Fear River in the northwest and northeast sections of the county, along the banks of inlet areas and the major streams, and the backsides of the barrier island beach communities. Elevation of the first floor of structures is required for development in this zone, as are mitigating measures such as flood openings and elevation of plumbing, electrical and mechanical equipment serving the structure. AE zones may also include a floodway, which is the area of the watercourse or stream and its’ immediate adjacent lands which must be reserved to effectively discharge waters of the base flood event. Floodways are more hazardous areas as they may see strong currents and fast-moving New Hanover County Floodplain Program 2 water; development in these areas are only permitted if a hydraulic analysis that shows that no increase to the base flood will occur is performed. Areas in the VE flood zones have the same quantitative annual chance of flooding as in the AE zone, but these areas have the potential for hazards such as velocity driven currents, wave action, or storm surge, and thus have a more rigorous design requirement for structures within. VE flood zones are primarily found immediately adjacent to open water bodies, such as on the oceanfront or sound front sides of the barrier islands and property fronting the intracoastal waterway, tidal creeks, and Cape Fear River. Mitigating construction requirements in this zone include elevation of the lowest horizontal structural member, breakaway walls, and certification that certain features must either be free of causing obstruction to floodwaters or be anchored in place and resist lateral movement or flotation are among the requirements for development in this zone. The coastal A zone serves as a transition area between the VE and AE zones, as it is expected that there is still the potential for limited effects from velocity driven currents, wave action, or storm surge. While these areas are technically delineated as A zones, construction requirements must adhere to V zone standards. The AO zone is an area that is characterized by shallow flooding, typically caused by sheet flow, ponding, or urban drainage issues; there is a small amount of land under this designation located in the Fort Fisher area. Although there are areas in the county with lower chances of flooding, such as those designated with a .2% or greater annual chance of flooding on the FIRMs, all development in flood zones should take into account the potential risks associated with flooding. Current Floodplain Management Regulations & Activities New Hanover County’s floodplain management program focuses largely on implementation of development guidelines, education and outreach, and mitigation and resiliency initiatives. As development proposals are submitted to staff for review and approval, all applicable regulations within Article 9 of the UDO are referenced to ensure that all new construction and substantial improvements meet these requirements and are constructed utilizing methods and practices that minimize flood damage. These generally include requirements governing structure and utility elevation, use of flood resistant materials, inclusion of mitigating features such as breakaway walls and flood openings, anchoring of certain components (i.e. pools), and limitations on fill, grading and excavation. On most structures, design and as-built certifications are required to document compliance. Adherence to these regulations is confirmed regularly by FEMA through Community Assistance Visits, where permitting and procedural records are analyzed to ensure that the community is upholding its commitment to sound floodplain management practices. In addition, the county participates in a voluntary floodplain management program called the Community Rating System (CRS). This program awards points on a tiered or class basis for various floodplain management practices including outreach efforts and events, preservation of open space, stormwater management, floodplain mapping initiatives, and complying with higher regulatory standards. The county’s current class rating of 7 out of 10 ultimately saves flood insurance policy holders 15% on premiums in the unincorporated county. In future years, an effort to improve this class rating will be conducted. County staff also regularly participate in educational opportunities with the general public, other agency staff, the development community, and higher education staff to promote awareness of New Hanover County Floodplain Program 3 flood mitigation opportunities and best practices. In addition, staff participate as applicable in program reforms and current topics such as flood insurance legislation. New Hanover County Northern Watersheds Flood Study The North Carolina Floodplain Mapping Program (NCFMP) was established in 2000 with a mandate to update flood mapping data for all 100 counties. Through a partnership with FEMA, the state was charged with creating and maintaining the Flood Insurance Rate Maps (FIRM) for all North Carolina communities. Since 2003, the NCFMP has analyzed, updated, and digitized the flood data for all 100 counties and associated communities. However, during subsequent updates to the mapping data sets, certain areas within the county were not provided detailed mapping studies, despite being physically located within the vicinity of or along the numerous waterways in the county. Areas of a community may not have a full detailed study performed due to cost, sparse development in a study area, or factors relating to a less likely risk of flood conditions. However, as development continues in the unincorporated areas of New Hanover County, especially in northern portions that are transitioning from agricultural and timberland to residential and commercial, the gaps in the flood mapping data should be analyzed since this information is required to inform a wide range of land use planning and policies for transportation, infrastructure design, water resources, environmental assessments, regulations/enforcement, and the formulation of comprehensive plans. With updated floodplain mapping data, prospective homeowners and developers will have access to additional information necessary for decision making. In 2021, county staff identified 12 study areas in the northern portion of the county where additional study and mapping of watersheds is necessary to provide adequate data to display potential flooding risks. Following a budget allocation to fund a study and a selection process, the county contracted with ESP Associates, Inc. to conduct a floodplain mapping study for these 12 locations within the county where the FIRMs do not have fully detailed mapping studies completed. This study has produced data and maps that will augment the existing FIRMs which have been produced in accordance with FEMA mapping standards. These mapping results will be used to provide additional data on flood risk in the study areas to improve awareness and resiliency in these areas. The Advisory Flood Hazard Areas were created using the same methodology used to produce the current FIRMs and encompass approximately 910 acres of property. New Hanover County Floodplain Program 4 Figure 1: Map of Advisory Flood Hazard Areas with Effective Special Flood Hazard Areas resulting from Watershed Mapping Mitigation and Resiliency Projects Beginning in 2022, county staff conducted an analysis of mitigation and resiliency efforts in order to provide a more coordinated, programmatic approach among all departments involved in related initiatives. Mitigation and resiliency initiatives will be identified, scoped, and prioritized internally so that future budget enhancement requests or grant funding opportunities can be pursued to address related strategic objectives. Examples may include planning or implementation projects such as watershed restoration and improvement plans, access, management, or mitigation plans, stormwater runoff studies, water quality enhancement projects, vulnerability analyses, improved outreach efforts on identified topics, and stream gauge installations.