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National Basin Delineation

National Basin Delineation. Project Team: Ken Howard Ami Arthur Gina Cox Dave Slayter Nathan Kuhnert Cooperative Institute for Mesoscale Meteorological Studies (CIMMS)/ National Severe Storms Laboratory (NSSL). National Basin Delineation. Project objective:

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National Basin Delineation

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  1. National Basin Delineation Project Team: Ken Howard Ami Arthur Gina Cox Dave Slayter Nathan Kuhnert Cooperative Institute for Mesoscale Meteorological Studies (CIMMS)/ National Severe Storms Laboratory (NSSL)

  2. National Basin Delineation Project objective: To delineate flash flood basins using a minimum drainage area threshold of 2 mi2 for use in the Flash Flood Monitoring and Prediction (FFMP) program.

  3. FFMP Basin Data Set Shapefiles 1) ****_orig_basins • A polygon shapefile of the original small basins (before aggregation). 2) ****_aggr_basins • A polygon shapefile of the aggregated basins within the radar coverage area. These are the basins for which the FFMP average rainfall values are calculated. • This is one of the two shapefiles required by FFMP. Any basin customization should ultimately result in a file named ****_aggr_basins with the specific attributes required by FFMP. 3) ****_str_gen • A polyline shapefile of the synthetic stream lines generated from the DEM.

  4. FFMP Basin Data Set Shapefiles 4) ****_bins • A point shapefile of the radar bin centerpoints with the associated Pfafstetter basin IDs (aggregated). • This is the second shapefile required by FFMP. 5) ****_nhd_rch • A polyline shapefile of stream lines from the National Hydrography Dataset (NHD). 6) ****_reg_nhd • A polygon shapefile of NHD waterbodies including lakes, reservoirs, ponds, and swamps.

  5. FFMP Basin Data Set ShapefilesAttributes in ****_aggr_basins a) Pfaf_id • 13-character Pfafstetter basin ID b) Streamname • Stream name as available from the NHD c) Huc • 8-digit HUC ID d) Huc_name • Name of the 8-digit HUC

  6. FFMP Basin Data Set ShapefilesAttributes in ****_aggr_basins e) X-outlet • Longitude of the basin outlet f) Y_outlet • Latitude of the basin outlet g) State • Two-character state abbreviation (based on basin outlet) h) CWA • Three-character county warning area ID (based on basin outlet)

  7. FFMP Basin Data Set ShapefilesAttributes in ****_aggr_basins i) Countyname • Name of the county j) FIPS • Five-character FIPS ID k) RFC • Five-character River Forecast Center ID (based on basin outlet) l) Modified • Flag to indicate whether a basin has been merged with other basins. 0 indicates a basin in its original state, 1 indicates a merged basin.

  8. FFMP Basin Data Set ShapefilesAttributes in ****_aggr_basins m) Reservoir • Flag to indicate whether a basin intersects a lake or reservoir according to those water bodies included in the NHD. 0 indicates no intersection with a reservoir, 1 indicates an intersection. n) Area_sq_mi • Basin area in square miles o) Flow_acc • An approximate flow accumulation value (in thousands of grid cells).

  9. FFMP Basin Data Set ShapefilesAttributes in ****_aggr_basins p) X_centroid • Longitude of the basin centroid q) Y_centroid • Latitude of the basin centroid

  10. FFMP Basin Data Set ShapefilesAttributes in ****_orig_basins The ****_orig_basins shapefile contains the same attributes as the ****_aggr_basins shapefile, with one additional field: Pfaf_aggr • Pfafstetter ID of this basin in the ****_aggr_basins shapefile In addition, the ****_orig_basins Pfafstetter ID field is named Pfaf_orig to distinguish it from the Pfaf_id field in ****_aggr_basins.

  11. FFMP Basin Data Set ShapefilesAttributes in ****_bins a) Azimuth_dg • Azimuth of the radar bin center point in degrees b) Range_km • Range of the radar bin center point in kilometers c) X_coord • Longitude of the radar bin center point d) Y_coord • Latitude of the radar bin center point e) Pfaf_id • Pfafstetter ID of the associated FFMP basin (aggregated)

  12. FFMP Basin Data Set ShapefilesProjection Information Projection: Geographic (lat/lon) Datum: NAD83 Units: Decimal Degrees Spheroid: GRS80

  13. FFMP Basin Data Set Shapefiles The ****_orig_basins shapefile contains all small basins in the HUCs covering the area. There is one stream reach per basin.

  14. FFMP Basin Data Set Shapefiles The ****_aggr_basins shapefile contains aggregated basins within the radar coverage area. There may be multiple stream reaches per basin.

  15. FFMP Basin Data Set Shapefiles The NHD reach and water body shapefiles are included for all HUCs covering the area. These are a good reference for "the real world".

  16. Sites to Receive Updated FFMP Basin Data Sets The following sites were converted to Geographic coordinates using an incorrect datum. This will NOT affect their use in FFMP. However, if other GIS data sets are overlaid, the basin shapefiles will be offset by the length of a few grid cells. For the most accurate results, any basin customization should be done using the updated version with the correct datum. The updated FFMP data sets will be delivered by the end of June.

  17. Sites to Receive Updated FFMP Basin Data Sets KENX,Albany,NY KFDR,Altus AFB,OK KAMA,Amarillo,TX KFFC,Atlanta,GA KBGM,Binghamton,NY KBMX,Birmingham,AL KBOX,Boston,MA KBUF,Buffalo,NY KCXX,Burlington,VT KCLX,Charleston,SC KCLE,Cleveland,OH KCAE,Columbia,SC KGWX,Columbus AFB,MS KFWS,Dallas-Ft. Worth,TX KDOX,Dover AFB,DE KDYX,Dyess AFB,TX KEVX,Eglin AFB,FL KFSX,Flagstaff,AZ KTYX,Fort Drum,NY KGRK,Fort Hood,TX KPOE,Fort Polk,LA KEOX,Fort Rucker,AL KSRX,Fort Smith,AR KGSP,Greer,SC KCBW,Houlton,ME KHTX,Huntsville,AL KJAN,Jackson,MS KJAX,Jacksonville,FL KEAX,Kansas City,MO KBYX,Key West,FL KMRX,Knoxville-Tri-Cities,TN KLCH,Lake Charles,LA KLZK,Little Rock,AR KLBB,Lubbock,TX KMXX,Maxwell AFB,AL KMLB,Melbourne,FL KAMX,Miami,FL KMOB,Mobile,AL KVAX,Moody AFB,GA KMHX,Morehead City,NC KOHX,Nashville,TN KLIX,New Orleans,LA KOKX,New York City,NY KAKQ,Norfolk-Richmond,VA KTLX,Oklahoma City,OK KDIX,Philadelphia,PA KPBZ,Pittsburgh,PA KGYX,Portland,ME KRAX,Raleigh-Durham,NC KFCX,Roanoke,VA KSHV,Shreveport,LA KSGF,Springfield,MO KCCX,State College,PA KLWX,Sterling,VA KTLH,Tallahassee,FL KTBW,Tampa,FL KEMX,Tucson,AZ KINX,Tulsa,OK KLTX,Wilmington,NC

  18. Basic Basin DelineationProcedure Begin with a Digital Elevation Model (DEM) • A digital map of terrain • Gridded or "raster" format • Rows & columns of elevations • Integer elevation values

  19. How are DEMs created? Created from various scale maps.... 1:24000 1:100000 1:250000

  20. A Bunch of Blocks to Represent the Earth

  21. A DEMWhat the Computer Sees & What You See

  22. Other Views

  23. DEM (90-meter)

  24. Basins Derived from the 90-meter DEM

  25. DEM (30-meter)

  26. Basins Derived from the 30-meter DEM

  27. The National Elevation Dataset (NED) • Produced at the USGS EROS Data Center • A 30-meter resolution seamless mosaic of 7.5-minute DEMs for the U.S. • Base DEMs have been edge-matched to ensure there are no gaps or missing data

  28. The National Elevation Dataset (NED) Filtering techniques have been applied to minimize artifacts from the original DEM creation methods.

  29. The National Elevation Dataset (NED) The NED is a dynamic dataset-updates are made when better quality or higher resolution DEMs are available.

  30. NSSL’s Partnership with the USGS EROS Data Center • NSSL assisted EROS with the “blind pass" processing for Stage 1 of their Elevation Derivatives for National Applications (EDNA) project. • This involved producing a hydrologically conditioned (filled) DEM, flow direction and flow accumulation grids, slope, contours, basins, and synthetic streams from the NED. • Access to the NED and basin delineation scripts, along with the guidance and expertise of several EROS scientists ensured the highest quality basin delineation attainable from a blind pass process.

  31. Delineation Methodology Begin with the USGS 8-Digit Hydrologic Cataloging Units of the U.S.

  32. Delineation Methodology 8-digit Hydrologic Unit Code (HUC) basin with a 25000-meter buffer. NED tiles covering the buffered area are merged and clipped.

  33. Delineation Methodology The DEM must be projected from Geographic coordinates to the Albers Equal Area projection with units in meters. Note: Basins should not be delineated in Geographic coordinates (lat/lon) because flow direction may be incorrectly derived.

  34. Delineation Methodology Projection Information Projection: Albers Equal Area Datum: NAD 83 Units: Meters Spheroid: GRS1980 Parameters: • 1st standard parallel 29 30 0.000 • 2nd standard parallel 45 30 0.000 • Central meridian -96 00 0.000 • latitude of projection’s origin 23 00 0.000 • false easting (meters) 0.00000 • false northing (meters) 0.00000

  35. Delineation Methodology Filling the DEM • “Sinks” in the DEM are filled to remove small imperfections in the data. • A sink is a cell with undefined drainage direction (all neighboring cells are higher elevations). • Sinks are filled to a point where water will flow out of the cell. • The pour point is the boundary cell with the lowest elevation for the contributing area of a sink.

  36. Delineation Methodology Flow Direction • Derived from the filled DEM • Each cell flows to a neighboring cell based on the steepest slope. 32 64 128 16 1 8 4 2

  37. Delineation Methodology Flow Direction Grid

  38. Delineation Methodology Flow Accumulation • Note that each grid cell flows into another grid cell and so forth. • One could tally or keep track of the total number of grid cells that flow into each “downstream” grid cell. • This is generally known as a flow accumulation data set. • Grid cells with high flow accumulation values are areas of concentrated flow and are identified as stream channels according to the specified flow accumulation threshold. • Grid cells with flow accumulation values of zero are topographic highs or ridges. This grid cell has a flow accumulation value of 15.

  39. Delineation Methodology Flow Accumulation Grid

  40. Delineation Methodology Stream Network • Derived from the flow accumulation grid. • Based on the specified minimum flow accumulation threshold. • Cells with flow accumulation greater than the threshold are designated as "stream channel" cells and will form the stream network. • A minimum flow accumulation threshold of 5000 grid cells (~1.74 mi2) was used to delineate the FFMP basins.

  41. Delineation Methodology

  42. Delineation Methodology Outflow Points • Outflow points are the cells with the maximum flow accumulation along a stream segment. • Derived from the flow accumulation and stream link grids.

  43. Delineation Methodology Catchments • Basins are delineated to each outflow point. • Derived from the flow direction and outflow point grids.

  44. National Basin Delineation Project Related Websites National Basin Delineation Project http://www.nssl.noaa.gov/wrd/wish/basins National Elevation Dataset (NED) http://edcnts12.cr.usgs.gov/ned Elevation Derivatives for National Applications (EDNA) http://edcnts12.cr.usgs.gov/ned-h National Hydrography Dataset (NHD) http://nhd.usgs.gov Pfafstetter Basin Codification System http://edcdaac.usgs.gov/gtopo30/hydro/P311.html

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