Digital Flood Insurance Studies & Their Development and Use

1. Digital Flood Insurance Studies &Their Development and Use

2. Start with Gathering Digital Data • GIS Based Digital Data • Base Maps • Aerial Topography • LiDAR • IFSAR • Digital Flood Insurance Rate Maps • Transition from Elevation Reference Marks to National Geodetic Survey Monuments • NAVD 88 Datum • Map Service Center

3. DTM TIN DEM Contours GIS Data Layers — Digital Terrain Modeling Formats

4. Topography Base + + Flood Data = Digital FIRM Components of a FloodMap

5. Base Data • Digital Orthophotogrammetric Quarter Quads (DOQQ) or community-supplied base • Will allow precise map determinationsby all users • Partner with USGS, States, and communities • DOQQs Available for 56% of U.S. • Additional 32% under production • Reduced cost for FEMA

6. Topography • Emerging technologies (LIDAR and IFSAR) allow for cost-effective, accurate collection of digital elevation data • Partner with NASA, USGS, States, & communities • LIDAR/IFSAR 20-50% of cost of collecting topographic data • GPS technology for field reconnaissance • Bathymetry • Hydraulic structures • Merge to build Digital Elevation Models

7. LIDAR • LIght Detection and Ranging (LIDAR) • Airborne Laser System • Fixed Wing • Helicopter • Potential for High Level accuracy (1 foot range) • Ongoing FEMA related projects: • Harris County, TX • Louisiana

8. IFSAR • Inter-Ferometric Synthetic Aperture Radar (IFSAR) • Airborne or spaceborne radar antennae • Accuracy levels between 1.5m and 3m over broad areas • Cover larger areas at lesser cost (and accuracy)than LIDAR

9. Global Positioning System(GPS) Surveys • Surveying with ground control established through satellite signals (xyz coordinates) • Airborne • Vehicle • Handheld • Boat with underwater depth finder • Used for stream channel and structure surveys to supplement LIDAR and IFSAR • Also useful for developing floodprone building inventory for conducting risk assessments • Vertical accuracy to 2cm • Very cost effective

10. FEMA Specifications • LIDAR specification developed for FISs, DEMs, and other NFIP products (this technology is not yet mature) • Performance-based calling for 30-cm (approximately 1-foot) accuracy • Robust QA/QC requirements • Only LIDAR specification currently available • Aerial mapping and surveying specifications being updated to include GPS, DOQQs, and LIDAR and IFSAR DEMs

11. Current Issues withLIDAR and IFSAR • Many FEMA initiatives and partnerships underway to evaluate • LIDAR specifications for DEMs and FISs developed • Rapidly Developing Technologies • Data voids—water and vegetation • Non-standard and varying results and costs; fuse with other technologies in near-term • GPS, Photogrammetric, & Microwave radiometer

12. Flood Data • Engineering analyses and digital mappingof flood risk • Use GIS-based hydrologic and hydraulic models integrated with DEMs (Automated H&H) • Contract with USACE, USGS, NRCS, local A/E firms, States, and communities

13. Linking base maps, work maps, and flood themes in GIS to a HEC-RAS model Automated Hydrology and Hydraulics • Use GIS and terrain-based models to automate and link: • Hydrologic modeling • Hydraulic modeling • Floodplain delineation • Automates QA/QC checking

14. DFIRM • Digital conversion of mapping inventory • Approximately 92,000 panels need conversion • Digital distribution (CD-ROM and Internet) allows for automated applications: • Risk assessment and mapdeterminations • Disaster response andrecovery • Repetitive loss applications • Planning and permitting • Supported by a fully integratedrelational and engineering database

15. Coastal Remote Sensing Hydrology Land Use Base Maps Hydraulics New DFIRMDatabase DEMs DFIRMs Surveying Applications Interface Automated Floodplain Delineations Coastal Models Hydrologic Models Hydraulic Models Applications DFIRM Database

16. DFIRM Database • Open file formats for data exchange across software applications • Efficient archiving and retrieval allows for rapid map updates and revisions • Supports GIS and software applications

17. Elevation Reference Marks Current • Benefits: • Elevation Reference Marks (ERMs) are located throughout the study area. • Location, Descriptions and elevations are included either on the FIRM panel or in the FIS Document. • Drawbacks: • ERMs do not have an horizontal location (x,y coordinates) • Many ERMs damaged or destroyed

18. NGS (National Geodetic Survey) Monuments – Map Modernization • Benefits: • NGS Monuments are available on-line. • NGS Monuments are maintained by the Federal government. • X, Y, and Z coordinates are available for every monument. These coordinates lend themselves to GPS surveying. • Drawbacks: • A limited number of NGS Monuments will be available for the County.

19. Conversion to NAVD 88 • The majority of existing FIRM panels vertical datums: • National Geodetic Vertical Datum (NGVD) 29 • Local Datum • New DFIRM Panel vertical datum will be standardized to (North America Vertical Datum) NAVD 88.

20. Layers of Digital Data • Easily updated • All data layers in Digital Flood Insurance Map can be easily modernized when changes occur • Can be overlaid with multiple datasets for comparison and integration • Creates useful products for communities

21. References • www.noaa.ngs.gov • www.fema.gov/mit/tsd/dl_cgs.htm