¶ How Can You Use BLE Data for Floodplain Management and Flood Risk Reduction Activities?
When your community receives Base Level Engineering (BLE) data, this data will likely be the Best Available Information (BAI) available to your community. As a result, your community will be responsible for navigating the "cans" and "cannots" of BLE:
Cans: These include requirements that your community must meet to comply with the NFIP, best practices, and opportunities to use BLE data to benefit your community. Flood risk reduction activities and higher standards beyond the minimum NFIP requirements are encouraged but not mandatory.
Cannots: These are ways and circumstances in which your community cannot use BLE (e.g., to set flood insurance rates).
¶ Communities Can Use BLE Data:
- For floodplain permitting accuracy in areas mapped into an Approximate Zone A (i.e., no flood elevations are provided on the Flood Insurance Rate Map [FIRM]) unless a more detailed study exists. Some permitting decisions include required building elevation heights and floodproofing measures.
- As BAI if the BLE-derived base flood elevations are more conservative (i.e., higher) than those on the effective FIRM.
- To identify flood hazard areas if the BLE shows an area as flood-prone that is not depicted as such on the effective FIRM.
¶ Ways to Use BLE
¶ 1. Best Available Information (BAI)
Adopt your BLE as BAI.
Communities can adopt BLE data as BAI through their local ordinance adoption process.
- NFIP regulations identify minimum requirements that communities must fulfill to join and stay in the program; some BLE products may not meet these minimums. Requirements may vary by community.
- BLE is only made regulatory when a community adopts it into its floodplain management ordinance. At this point, it ceases to be BLE and becomes regulatory flood data.
- Insurance agents and lenders must use the effective FIRM when setting insurance rates and determining flood insurance requirements.
- Flood insurance premiums and requirements may only change for a property when the effective FIRM is revised or amended.
Example Ordinance Provision:
"The Community has elected to adopt [Title of Study] Base Level Engineering data as Best Available Information to regulate its floodplain development, supplemented by the effective FIRMs and FIS.
Where Best Available Information contradicts the FIRMs or FIS, the Community shall use the more restrictive data."
¶ 2. Risk Assessment and Analysis
Understand what is changing.
BLE data can be used to understand a community’s exposure to flood risk and estimate the potential impacts of flood events. Potential use cases include:
-
Identifying structures newly added to flood hazard areas.
-
Identifying areas that have a higher flooding probability and are more likely to incur frequent losses.
-
Analyzing asset vulnerability by comparing flood depths to an asset’s footprint.
-
Understanding where buildings and other infrastructure may experience greater damage from intense hydrodynamic forces of fast-moving water.
.png)
BLE Floodplain Boundary Maps show where assets are located in relation to areas of flood risk..png)
BLE Depth Grids show how deep floodwater may get during a flood.
BLE data can be used as input to Hazus to estimate the economic loss from flood events. Managed by FEMA's Natural Hazards Risk Assessment Program, Hazus is a standardized methodology that uses state-of-the-art GIS software to combine inventory information, hazard extent and intensity data, and damage functions to display hazard data and estimate disaster impacts, such as structural damage and economic loss in dollars.
Losses are less likely to be underestimated when using BLE data instead of effective data, as BLE may provide a greater amount of information (i.e., more miles of mapped streams) on which to base loss values.
¶ 3. Enhanced Flood Mapping
BLE can be compared with the effective FIRM's Special Flood Hazard Area (SFHA) boundaries to identify discrepancies in mapped flood risk. Potential use cases include:
-
Using new, detailed flood information to identify high-risk areas not currently mapped into the SFHA.
-
Analyzing floodplain boundaries and depth to approximate a flood event's impact on given location.
-
Identifying vulnerable areas or critical open space not marked on the effective FIRM.
.jpg)
BLE Depth Grids can inform zoning decisions and keep critical facilities and residences out of harm's way. Image Source
¶ 4. Mitigation and Planning
Local governments can perform BLE-informed risk analyses to prioritize projects and risk reduction measures. Potential actions include:
-
Comparing flood extents with building footprints and community maps to determine areas of higher and lower risk.
-
Making informed decisions about where development is suitable, what kinds of developments or mitigation projects may be appropriate, and where conservation of open space may help decrease the occurrence, extent, and severity of flood damage.
-
Determining the best flood protection measures to incorporate into site and building design.
-
Evaluating transportation and evacuation routes.
.jpg)
BLE can help determine appropriate structural and nature-based projects to reduce flood risk.
¶ 5. Grant Applications and Capital Requests
Fund projects to address flood risk.
BLE data can be used to justify fiscal support from grant or capital programs. Possible uses include:
- Supporting the request narrative using maps and figures.
- Showing need and urgency with vulnerability and impact data.
BLE can be used to show the need, urgency, and impact of mitigation projects. Image Source
.jpg)
BLE can be reformatted and tailored to individual grant applications, as some grants require specific types of data inputs.
¶ 6. Updating Regulations
Inform higher regulatory standards.
BLE data can guide management standards that exceed NFIP requirements in areas where flood hazards have not yet been identified or mapped or in areas that have been mapped into the floodplain but lack flood elevation data. If your community chooses to adopt BLE data as the regulatory standard, you may choose to do the following:
- Require additional flood risk information and associated documentation in permit applications (Elevation Certificates, Floodproofing Certificates, Substantial Damage and Improvement determinations, etc.).
- Require buildings to adhere to certain design specifications beyond those that FEMA established standards, such as higher standards for minimum elevations and floodproofing measures.
- Place restrictions or limitations on the use of fill for development when necessitated by flood safety standards.
.jpg)
BLE can demarcate areas of fill use before they appear on the FIRM.
.jpg)
BLE can inform the boundaries of critical facility locations.