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

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

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

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

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

9. 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.

10. SRTM Coverage 56°S to 60°N

11. 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 US http://edcwww.cr.usgs.gov/Webglis/glisbin/guide.pl/glis/hyper/guide/u sgs_demLink Link for Texas http://www.tnris.state.tx.us/DigitalData/DEMs/dems.htmLink

12. National Elevation Dataset 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/Link

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

14. 7.5´ 1º 1” and 3” DEMs 30m DEM Coverage of 30m, 1” and 3" DEMs

15. 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 Link http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/ndcdb.htmlLink

16. Cell Size 30m100m

17. 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 Link http://edcwww.cr.usgs.gov/landdaac/gtopo30/gtopo30.htmlLink

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

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

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

21. 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

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

23. Topographic Map Austin West, 1:24,000 Scale http://www.tnrcc.state.tx.us/gis/raster.html 20 ft contour 100 ft contour Stream Center Line

24. Flow in Direction of Steepest Descent

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

26. 200 Meter Mesh (Universal Transverse Mercator Coordinates) 1km

27. 100 Meter Mesh (UTM Coordinates) 100m 1km

28. 30 Meter Mesh Standard for 1:24,000 Scale Maps

29. Austin West 30 Meter DEM Elevations in meters ftp://ftp.tnris.state.tx.us/tnris/demA.html

30. USGS 30 Meter DEM for This Area

31. 30 Meter DEM Cell Boundaries

32. DEM Lattice Points

33. DEM Cell Stores Elevation at Lattice Point

34. DEM Elevations Contours 720 700 680 740 680700720740 720

35. DEM Elevations Contours 700 680

36. 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

37. 6756494650 121112 5344373848 5855223124 6147211619 3453 Digital Elevation Model

38. 6756494650 121112 5344373848 5855223124 6147211619 3453 50 cell size cell (cell value) Cell Definition

39. 32 16 8 64 4 128 1 2 Eight Direction Pour Point Model

40. 675649 534437 585522 1 675649 534437 585522 1 Slope: Direction of Steepest Descent

41. 22448 1216 12484 1281248 21444 11 Flow Direction Grid

42. Austin West 30 Meter DEM Elevations in meters ftp://ftp.tnris.state.tx.us/tnris/demA.html

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

44. Grid Network

45. 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

46. 00000 0 0 0 0 0 0 0 0 032 2 11 1 1 15 25 24 1 00 0 00 0 0 0 0 0 0 0 0 0 322 11 1 1 1 2 15 245 Flow Accumulation Grid LinkLink to Grid calculator

47. 00 0 00 0 0 0 0 0 0 0 0 0 322 11 1 1 1 2 15 245 Flow Accumulation > 5 Cell Threshold

48. Stream Network for 5 cell Threshold Drainage Area 00000 0 0 0 0 0 0 0 0 032 2 11 1 1 15 25 24 1

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

50. + =  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 “Burning In” the Streams

51. Filling in the Pits DEM creation results in artificial pits in the landscape A pit is a set of one or more cells which has no downstream cells around it Unless these pits are filled they become sinks and isolate portions of the watershed Pit filling is first thing done with a DEM

53. 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

54. Watershed Outlet

55. Watershed Draining to This Outlet

56. Watershed and Drainage Paths Delineated from 30m DEM Automated method is more consistent than hand delineation

57. 00000 0 0 0 0 0 0 0 0 032 2 11 1 1 15 25 24 1 Stream Segments

58. 5 5 1 1 1 3 2 2 3 3 4 4 4 4 4 5 5 6 6 6 Stream Segments in a Cell Network

59. 989510 1504 (>1000) 1000 Cell Threshold Exceeded at Stream Junction

60. Same Cell Value Subwatersheds for Stream Segments

61. Vectorized Streams Linked Using Grid Code to Cell Equivalents Vector Streams Grid Streams

62. Delineated Subwatersheds and Stream Networks

63. Summary Concepts Topographic maps are the traditional way of representing land surface terrain and streams Watersheds can be hand-delineated from these maps DEM’s of equivalent accuracy are now available for most map series in the US

64. Summary Concepts (2) DEM cell elevation is at the cell center eight direction pour point model leads to flow direction and flow accumulation grids stream network is defined as cells whose flow accumulation exceeds a threshold watershed outlet is the cell with highest flow accumulation

65. Summary Concepts (3) Streams can be divided into links and subwatersheds defined for them Resulting grids can be vectorized Standardized DEM data sources: 30m, 1” 3”, 30” Coverage from local scale to the whole earth