1. FEMA-MOTF@fema.dhs.gov HWM Depth Grid Process Overview

2. FEMA-MOTF@fema.dhs.gov Data Acquisition Terrain Data - Raster Best available dataBest available data USGS National Map (NED) http://nationalmap.gov/USGS National Map (NED) http://nationalmap.gov/ http://nationalmap.gov/ Available nationally at resolutions of 1 arc-second (about 30 meters), 1/3 arc- second (about 10 meters)Available nationally at resolutions of 1 arc-second (about 30 meters), 1/3 arc- second (about 10 meters) 1/9 arc-second resolution data is very limited in coverage for most areas of the U.S.1/9 arc-second resolution data is very limited in coverage for most areas of the U.S. LiDAR available through local municipalitiesLiDAR available through local municipalities High Water Mark Data - Vector Multiple collection methodsMultiple collection methods Field Survey’sField Survey’s Tape Measure and GPSTape Measure and GPS Must be collected in the fieldMust be collected in the field SLOSH – Coastal FloodingSLOSH – Coastal Flooding ***NGVD 29 vs NAVD 88*** ***NGVD 29 vs NAVD 88*** Make sure all data are in the Make sure all data are in the same vertical datum same vertical datum

3. FEMA-MOTF@fema.dhs.gov Add Terrain and HWM data

4. FEMA-MOTF@fema.dhs.gov Interpolate the Water Surface

5. FEMA-MOTF@fema.dhs.gov Subtract WSE from DEM

6. FEMA-MOTF@fema.dhs.gov Remove Negative Values

7. FEMA-MOTF@fema.dhs.gov Convert to Polygon

8. FEMA-MOTF@fema.dhs.gov Extract Flood Boundary

9. FEMA-MOTF@fema.dhs.gov Extract Depth Grid

10. FEMA-MOTF@fema.dhs.gov Process Overview

11. FEMA-MOTF@fema.dhs.gov Useful Links USGS NED - http://nationalmap.gov/USGS NED - http://nationalmap.gov/http://nationalmap.gov/ Vertcon Conversion -Vertcon Conversion - http://www.ngs.noaa.gov/cgi- bin/VERTCON/vert_con.prlhttp://www.ngs.noaa.gov/cgi- bin/VERTCON/vert_con.prl MOTF SOPs – https://content.femadata.com/MOTF/SOPs/MOTF SOPs – https://content.femadata.com/MOTF/SOPs/https://content.femadata.com/MOTF/SOPs/ US Interagency Elevation Invnetory - http://coast.noaa.gov/inventory/US Interagency Elevation Invnetory - http://coast.noaa.gov/inventory/ http://coast.noaa.gov/inventory/