Better Defining the Flood Threat Flood Inundation Mapping from the National Weather Service

Better Defining the Flood ThreatFlood Inundation Mapping from the National Weather Service2009 Severe Storms and Hydrology ConferenceShreveport, LA

Gregory P. SheltonNWS/West Gulf River Forecast Center

West Gulf River Forecast Center

ADVANCED HYDROLOGIC PREDICTION SERVICEHow can you get the river and rainfall information you need?


Advanced Hydrologic Prediction ServiceState of the science forecastingShort and long term probabilistic forecastsWater supply forecastsInundation mappingInnovation at all timescalesFlash flood modelingDistributed modelingEnsemble modeling


Goals of AHPSProvide emergency and water resource managers information To make informed risk-based decisions To optimize the use of resourcesBetter meet the hydrologic needs of the country Plan with confidence and efficiencyStay out of harms wayProvide valuable water supply informationEnable the NWS to increase forecast skill and warning lead time


http://water.weather.govAccess to most NWS forecasts and dataOne internet address


Rainfall - PastNational Image is composed of Best Estimate QPE from the 12 CONUS RFCs


http://water.weather.govAccess to most NWS forecasts and dataOne internet address


River Information


River Information


River Information


INUNDATION MAPPINGBetter Defining the River Flood Threat


Customer InputFamiliarity with NWS flood severity categoriesUtility of existing flood severity categoriesRetain existing flood severity categoriesEnhance communication of flood risk by use of inundation graphics (maps)


Graphical Flood Impact Information

Partnered with NC Floodplain Mapping Program Office, FEMA, and USGS to develop user-requested graphics to better convey flood threatNeuse River at Goldsboro, NC


Initial StepsUsed partnered data (LIDAR Topo Engineering Data) from FEMA and NC Floodplain Mapping ProgramBuilt unsteady hydraulic model for 73 miles of Tar RiverMapped flood forecasts in a GIS and presented results in easy to read format over the Web. (Text To Graphics)Used operationally by SERFC as flood forecast tool during Hurricane Isabel Sept. 2003Tar River Basin, NCGoal To provide Web based flood inundation maps from the NWS operational forecast environment to emergency managers during flood events.


Static Libraries


Inundation Mapping ProcessObtain and QC Base DataLIDAR, Topography, Aerial photography, Rating curves, Engineering data (preferably completed FIS)Close collaboration with partners and customersFEMA, River Authorities, USGS, Local EMsDevelop Flood ProfilesDetermine boundaries for hydraulic modeling of reachDetermine mapping intervals (1 ft, 2 ft, 4ft, etc.)Develop flows that match rating curve stage for the mapping intervals Export profiles to GIS for predetermined levelsDatum consistency!!Develop/Deploy Public Mapping LibrariesQA/QC by NWS staff Flood depth grids and Inundation polygons delivered to contractor for development of web deliverablesFinal product pushed to AHPS web pages


QA/QC ProcessCheck GeoDataLat/Lon at gage locationStream centerlineRoadsCheck for non-contiguous inundation areasCheck for correct reference dataFlood categoriesImpacts statementsHistorical crests


Available ProductsMap typesPredefined LevelsFlood CategoriesCurrent ForecastOverlaysStreet mapsAerial photosMap ToolsZoomMouse over for water depthExport to multiple formats (including shapefiles)Current forecast zoomed to forecast pointFlood categories zoomed to nearby neighborhoodFull map with aerial photo and predefined height displayed


Initial Inundation Mapping Locations


Inundation Mapping for TexasMost locations currently available All available by end of 2009Partnerships with local governments and river authoritiesAdditional locations also possible


Current Locationshttp://www.weather.gov/ahps/inundation.php


Example Buffalo Bayou at Shepherd DrivePredefined river stage levels and associated NAVD88 elevation. Yellow highlight indicates current level displayed.Standard and Detailed image options Depth of water analysis available with Detailed Image


Example Buffalo Bayou at Shepherd DriveFlood Categories available as overlays100 & 500 Year Floodplains and Floodway Data available as overlays


Example Buffalo Bayou at Piney PointCurrent Forecast:60.3 FT at 18 UTC on 4/28/09

Current Forecast:56.6 FT at 00 UTC on 4/29/09


Hurricane IkeSequoia Estates: 56.359 S bound feeder: 55.2N side channel: 54.9Greens Bayou at U.S Hwy 59 Crest 58.4 feet


IBWC PartnershipGoal: Implement FIM on the Rio GrandeWMO Voluntary Cooperation ProgramSeeking funding to cover implementationWorked with IBWC to develop grant proposalUtilize existing base data and modeling from IBWC Approval delayed and project merged with larger bi-national negotiationsIBWC completed primary modeling work between Amistad and Falcon ReservoirsPartnering to perform QC of polygonsSeeking new funding sources to cover implementation State of Texas


Potential Mapping LocationsMapping nearing completionFuture potential mapping locations


Questions/Comments?Contact Info:Gregory P. Shelton, Service Coordination HydrologistWest Gulf River Forecast [email protected](817) 831-3289 x219

*Answers How high will the river rise?When will the river reach its peak?Where will property be flooded?How long will flooding last?What volume of water will enter a reservoir?When and where will snowmelt peaks occur?How long will low flow conditions persist?**When you go to the AHPS web page, you will see a map of the more than 3000 river gages across the United States including American SamoaGuam Puerto Rico and the Virgin islands. Many of these sites are USGS gages and report on intervals of an hour or less. This helps the National Weather Service monitor these gages 24 hours a day 7 days a week for the threat of flooding. Note the map on the left where floods or high water is depicted by a color code. Want to go to a smaller scale for better resolutionjust click on your area of interest.Clicking on the map will zoom you in to the local area of interest with the river gages and their associated locations. Notice the legend is again available and the gage locations are color coded to the different flood categories or even showing a near flood stage status. This map view map provide you an awareness to the extent of the river flooding in your area but what about actually seeing how high a river is going to get*That is simple. Just click on the gage location and there you have ita new page will come up with the graph of the river stage over time, or what is often called a hydrograph. The user can see the overall observed trend of the river in addition to how it relates to the different flood level categories. If there is a forecast issued and available, then this would also be shown on the graph*In addition to the hydrograph shown on the web page, various other information can be found including a map of the location of the gage, the different impacts flood waters may have at different stages, historical crests, and stage levels for each category of flooding.Of particular importance is the flood category levels as they depict the magnitude or severity of flooding. These levels are set through the cooperation of the particular National Weather Service Forecast Office Service Hydrologist or Hydrologic Program Focal Point and the emergency management agencies in that area. For the emergency management community, when it comes to flood preparation and taking action to mitigate loss of life and property before a flood wave, knowing these levels and working with your local Weather Forecast Office to make sure they are right is critical.****((1) Check BaseMap - Gage location - Stream Centerline - Roads, Highways, and other Vector lines. - Features edged-map properly on main panel. (2) Review each inundation and water depth maps are reasonable approximation for every associated stage/elevation level in both Standard and Detailed View. - Check for unconnected water surface areas (dangles) that should be removed - Check for overconnected areas (pseudo-nodes and overlaps) that should be removed - Inundation Study Limits/Boundaries - Identify areas where water depths are too deep (shallow) or not deep enough (depressions) - Depiction of flood categories. - Check high water surveys - Check flood impacts are reasonably approximated on the map - Check historical crests are mapped - Check whether mapping was performed at reasonable lower bounds (i.e. action levels or lower). (3) Review digitized features. - FEMA Regulatory Zones 100, 500 , Floodway (4) Review Web Interface Functionality - Arrow features - Zoom features - Mouse-over on water depth - Flood Categories (individually and as an additive overlay) - Check transparency level - Evaluate attributions - Check Print Save Feature

Documents

Better Defining the Flood Threat Flood Inundation Mapping from the National Weather Service