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DEM’s, Watershed and Stream Network Delineation

DEM’s, Watershed and Stream Network Delineation. DEM Data Sources Study Area in West Austin with a USGS 30m DEM from a 1:24,000 scale map Eight direction pour point model (flow direction and flow accumulation grids) Stream network definition Watershed delineation. DEM Data Sources.

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DEM’s, Watershed and Stream Network Delineation

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  1. DEM’s, Watershed and Stream Network Delineation • DEM Data Sources • Study Area in West Austin with a USGS 30m DEM from a 1:24,000 scale map • Eight direction pour point model (flow direction and flow accumulation grids) • Stream network definition • Watershed delineation

  2. DEM Data Sources • Shuttle Radar Topography Mission (SRTM) • 30m DEMs from 1:24,000 scale map • 1” National Elevation Dataset • 3" (100m) DEMs from 1:250,000 scale maps • 30" DEM of the earth (GTOPO30)

  3. Santa Barbara, California http://srtm.usgs.gov/srtmimagegallery/index.html

  4. San Andreas Fault, California http://srtm.usgs.gov/srtmimagegallery/index.html

  5. Salt Lake City, Utah http://srtm.usgs.gov/srtmimagegallery/index.html

  6. Mt Kilimanjaro, Tanzania http://srtm.usgs.gov/srtmimagegallery/index.html

  7. Shuttle Radar Topography Mission (SRTM) • 1 arc-second elevation data for the United States, 3 arc-second data for the globe • Produced by radar measurements from a Shuttle mission, Feb 11-22, 2000 • http://srtm.usgs.gov/data/obtainingdata.html

  8. Interferometry used by SRTM In interferometry, two images are taken from different vantage points of the same area. The slight difference in the two images allows scientists to determine the height of the surface.

  9. SRTM Coverage 56°S to 60°N

  10. 30m DEMs • Best resolution standardized data source available for the US • Coverage of the country is incomplete • Data by 7.5’ map sheets in UTM projection • Link for UShttp://edcwww.cr.usgs.gov/Webglis/glisbin/guide.pl/glis/hyper/guide/usgs_dem • Link for Texas http://www.tnris.state.tx.us/DigitalData/DEMs/dems.htm

  11. Seamless 1” DEM for the US in 1° x 1° blocks Compiled by synthesizing the 30m DEM’s from 1:24,000 scale maps Link to website http://edcnts12.cr.usgs.gov/ned/ National Elevation Dataset

  12. http://seamless.usgs.gov/ Seamless Data Distribution http://edcnts14.cr.usgs.gov/Website/store/viewer.htm

  13. Coverage of 30m, 1” and 3" DEMs 1” and 3” DEMs 1º 30m DEM 7.5´ 7.5´ 1º

  14. 3” DEMs • Derived by US Defence Mapping Agency, available from USGS for the whole US • Data in geographic coordinates by 1;250,000 map sheet names (1ºx 1º) cells in (1ºx 2º) maps • Needs to be projected to planar coordinates • Linkhttp://edcwww.cr.usgs.gov/doc/edchome/ndcdb/ndcdb.html

  15. Cell Size 30m 100m

  16. 30" DEM GTOPO30 • Produced by USGS from 3" grids and Digital Chart of the World topography • Coverage complete for the earth • Projected cell size is 1km • Data must be projected before use • Linkhttp://edcwww.cr.usgs.gov/landdaac/gtopo30/gtopo30.html

  17. GTOPO30 Source: http://edcwww.cr.usgs.gov/landdaac/gtopo30/gtopo30.html

  18. Drainage in North America Source: http://edcwww.cr.usgs.gov/landdaac/gtopo30/hydro/namerica.html

  19. Drainage Basins of North America Source: http://edcwww.cr.usgs.gov/landdaac/gtopo30/hydro/na_basins.html

  20. DEM’s, Watershed and Stream Network Delineation • DEM Data Sources • Study Area in West Austin with a USGS 30m DEM from a 1:24,000 scale map • Eight direction pour point model (flow direction and flow accumulation grids) • Stream network definition • Watershed delineation

  21. Study Region in West Austin Hog Pen Ck 4 km 4 km

  22. Topographic MapAustin West, 1:24,000 Scalehttp://www.tnrcc.state.tx.us/gis/raster.html 20 ft contour 100 ft contour Stream Center Line

  23. Flow in Direction of Steepest Descent

  24. Watershed Delineation by Hand Digitizing Watershed divide Outlet Drainage direction

  25. 200 Meter Mesh (Universal Transverse Mercator Coordinates) 1km 1km

  26. 100m 100 Meter Mesh (UTM Coordinates) 1km 100m 1km

  27. 30 Meter MeshStandard for 1:24,000 Scale Maps

  28. Austin West 30 Meter DEMElevations in meters ftp://ftp.tnris.state.tx.us/tnris/demA.html

  29. USGS 30 Meter DEM for This Area

  30. 30 Meter DEM Cell Boundaries

  31. DEM Lattice Points

  32. DEM Cell Stores Elevation at Lattice Point

  33. DEM Elevations 720 720 Contours 740 720 700 680 740 720 700 680

  34. DEM Elevations Contours 700 680

  35. DEM’s, Watershed and Stream Network Delineation • DEM Data Sources • Study Area in West Austin with a USGS 30m DEM from a 1:24,000 scale map • Eight direction pour point model (flow direction and flow accumulation grids) • Stream network definition • Watershed delineation

  36. 67 56 49 46 50 53 44 37 38 48 58 55 22 31 24 61 47 21 16 19 53 34 12 11 12 Digital Elevation Model

  37. 67 56 49 46 50 53 44 37 38 48 58 55 22 31 24 61 47 21 16 19 53 34 12 11 12 Cell Definition cell size 50 (cell value) cell

  38. 32 64 128 16 1 8 4 2 Eight Direction Pour Point Model

  39. 67 56 49 53 44 37 58 55 22 Direction of Steepest Descent 1 1 67 56 49 53 44 37 58 55 22 Slope:

  40. 2 2 4 4 8 1 2 4 8 4 128 1 2 4 8 2 1 4 4 4 1 1 1 2 16 Flow Direction Grid

  41. Austin West 30 Meter DEMElevations in meters ftp://ftp.tnris.state.tx.us/tnris/demA.html

  42. 32 64 128 16 1 8 4 2 Flow Direction Grid

  43. Grid Network

  44. DEM’s, Watershed and Stream Network Delineation • DEM Data Sources • Study Area in West Austin with a USGS 30m DEM from a 1:24,000 scale map • Eight direction pour point model (flow direction and flow accumulation grids) • Stream network definition • Watershed delineation

  45. Flow Accumulation Grid 0 0 0 0 0 0 0 0 0 0 0 3 2 2 0 3 2 0 0 2 0 0 1 0 0 11 0 1 0 11 0 0 0 1 15 0 0 1 0 15 1 0 2 5 24 2 5 0 1 24 Link to Grid calculator

  46. 0 0 0 0 0 0 3 2 2 0 0 1 0 0 11 0 0 0 1 15 1 0 2 5 24 Flow Accumulation > 5 Cell Threshold

  47. Stream Network for 5 cell Threshold Drainage Area 0 0 0 0 0 3 2 0 0 2 0 0 1 0 11 0 0 1 0 15 2 5 0 1 24

  48. Streams with 200 cell Threshold(>18 hectares or 13.5 acres drainage area)

  49. “Burning In” the Streams  Take a mapped stream network and a DEM Make a grid of the streams Raise the off-stream DEM cells by an arbitrary elevation increment  Produces "burned in" DEM streams = mapped streams = +

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