Floodplain Management

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Floodplain Mapping

Flood studies and floodplain mapping projects are conducted to identify flood risk so communities can make informed decisions related to floodplain management. There are many products used to convey flood risk, which wil be detailed in the following sections.

 

Floodplain Mapping Categories

The Department of Natural Resources works in partnership with the Federal Emergency Management Agency (FEMA) to produce floodplain mapping products in adherence to National Flood Insurance Program (NFIP) requirements and regulations.

Basic Mapping

Mapping determined using approximate methodologies which defines areas subject to 1%-annual-chance flooding (Zone A) and 0.2% annual-chance flooding (Shaded Zone X). Basic mapping does not consider structures, but is based only on bare earth topography.

Because detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply.

 

arial view of land with a blue area marked over the top

Enhanced Mapping

Mapping determined using detailed methods which defines areas subject to 1%-annual-chance flooding (Zone AE) and 0.2%-annual-chance flooding (Shaded Zone X). Enhanced study areas show Base Flood Elevations (BFEs) on the maps and typically define a Floodway.

A floodway reserves land adjacent to the stream to convey the 1%-annual-chance-flood event without cumulatively increasing the base flood elevation more than one-foot. Communities must regulate development within the floodway to ensure there are no base flood elevation increases.

 

arial view of land with a blue area with stripes marked over the top

Flood Awareness Areas

Flood Awareness Areas are floodplain boundaries that are produced by NeDNR which can be used as “best available data” for communities involved in a current mapping project, those that do not have regulatory floodplain boundaries, or those that have outdated floodplain information.

NeDNR delineates flood awareness areas to provide communities with the most accurate flood risk information. NeDNR flood awareness areas can be viewed on our Floodplain Interactive Map.

 

arial view of land with a blue flood area marked over the top

Products that Convey Flood Risk

The Department of Natural Resources works in partnership with the Federal Emergency Management Agency (FEMA) to help community members and officials view and visualize their local flood risk, allowing communities to make informed decisions about reducing flood loss and mitigating potential damage from flood hazards.

Digital Flood Insurance Rate Maps (DFIRMS or FIRMS)

DFIRMs are FEMA products that depict areas prone to flooding during the 1%-annual-chance flood (Zone A / Zone AE) and the 0.2%-annual-chance flood (Shaded Zone X). DFIRMs are considered regulatory products for communities to use for floodplain management and for flood insurance rating purposes.DFIRMs can be viewed or downloaded from the FEMA Map Service Center.

NeDNR Role: NeDNR partners with FEMA to conduct floodplain mapping to update the DFIRM products for areas prioritized through the FEMA RiskMAP program. FEMA provides financial support for NeDNR to conduct these studies, which allow NeDNR to meet our statutory responsibilities to provide flood risk data and promote effective floodplain management to the citizens of Nebraska.

 

FIRM Panel map

Flood Insurance Study (FIS)

The FIS explains the study methods used in creation of the floodplain boundaries, as shown on DFIRMs. It also contains profiles for enhanced study areas. FIS documents can be downloaded from FEMA’s Map Service Center.

 

Jefferson FIS Map

Base Flood Elevations (BFES)

A BFE is the height that flood waters are anticipated to reach at a given location in the event of the 1%-annual-chance flood (base flood). The FIS, not the DIFIRM, should be used to determine BFEs in enhanced study areas. For areas mapped using approximate methods, BFEs need to be determined using FEMA accepted methods.

In certain instances, NeDNR provides BFE Determinations to Floodplain Administrators, upon request, for distribution to stakeholders applying for permits for Letters of Map Changes. If you are a Floodplain Administrator and would like to request a BFE, click here. If you are a homeowner, lender, engineer, or contractor and wish to request a BFE, please contact your Floodplain Administrator.

 

arial view of land with a blue striped area marked over the top

Letters of Map Change (LOMC)

LOMCs are documents that depict changes made to DFIRMs because of revised flood studies or updated information in a localized area. LOMCs are often submitted due to updated engineering data, construction of a flood risk reduction project, or to clarify the floodplain map at locations, such as at one particular residence, too small to be seen on a map.

NeDNR's Digital Work Maps

Digital Work Maps are floodplain maps that are produced by NeDNR which can be used as best available data for communities that do not have DFIRMs or those that have outdated DFIRMs. NeDNR produces work maps to provide communities with the most accurate flood risk information.

The maps are created using FEMA mapping standards, so communities have the option of adopting the Work Maps for local planning and building purposes, while also using FEMA regulatory products. NeDNR work maps can be viewed on our Floodplain Interactive Map.

 

arial view of land with a blue area marked over the top

Flood Risk Products

As part of new floodplain mapping projects, additional products are created to show more detail than just the 1% and 0.2%-annual-chance flood boundaries. These products give communities information related to depth of flood water, probability of flooding occurring at a specific location each year, probability of flooding occurring at a specific location over the course of a 30-year mortgage, areas of mitigation interest, and changes in floodplain boundaries from the previous FEMA FIRMs.

Click here to view the FEMA Risk MAP Flood Risk Products Fact Sheet. To view Flood Risk products available in Nebraska, please visit our Flood Risk Products Interactive Map.

 

arial view of land with the flood risk area marked over the top

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