1. Map-Based Flood Hydrology and Hydraulics David R. Maidment Jan 10, 1998

2. Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

3. Map-Based Hydrology and Hydraulics ArcView Input Data DEM HEC-HMS Flood discharge HEC-RAS Water surface profiles ArcView Flood plain maps CRWR-PrePro

4. Austin Digital Elevation Model Waller Creek

5. Austin Watersheds

6. CRWR-PrePro ArcView-based preprocessor for HEC-Hydrologic Modeling System (HEC-HMS) Digital Elevation Model Stream Map HMS Basin File Control point locations

7. Presentation Outline Using GIS to connect hydrology and meteorology Representation of spatial objects in GIS Terrain analysis using Digital Elevation Models Geodesy and map projections

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

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

10. 30 Meter Mesh Standard for 1:24,000 Scale Maps

11. DEM Elevations Contours 720 700 680 740 680700720740 720

12. DEM Elevations Contours 700 680

13. 32 16 8 64 4 128 1 2 Eight Direction Pour Point Model

14. 675649 534437 585522 1 675649 534437 585522 1 Slope: Direction of Steepest Descent

15. 22448 1216 12484 1281248 21444 11 Flow Direction Grid

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

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

18. Grid Network

19. 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

20. 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

21. 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

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

23. Watershed Outlet

24. Watershed Draining to This Outlet

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

26. DEM Data Sources for Texas Digital terrain models with 2’ or 4’ contours built from aerial photogrammetry 10m DE-DEMs, from 1:24,000 scale maps with drainage enforcement (experimental) 30m DEMs from 1:24,000 scale maps 1” seamless DEM of Texas (March, 1999) 3" (100m) DEMs from 1:250,000 scale maps (current state-wide coverage)

27. DEM Watersheds for Austin

28. Selected Watersheds and Streams Mansfield Dam Colorado River

29. HMS Schematic Prepared with CRWR-PrePro Mansfield Dam Colorado River

30. HMS Basin File Basin file is a text description of all hydrologic elements 155 33 87 39Subbasin Junction Reach

31. HMS Model of the Austin Region

33. Maps Served on the Web

34. Design Precipitation Input

35. HMS Control File

36. HMS Results Watershed 155Junction 44

37. Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

38. Regional flood analysis in Houston Study region

39. Study Region in West Houston Maps Developed using CRWR-Prepro by Seth Ahrens

40. Nexrad Rainfall for Storm of Oct 1994

41. Discharge in Buffalo Bayou at Katy October, 1994 storm

42. Calibrated Flow with HEC-HMS

43. Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

44. Waller Creek DEM

45. Waller Creek Watershed Outlets

46. Waller Creek HMS Model

47. Flood Plain Mapping

48. Connecting HMS and RAS

49. Discharge at a Particular Cross-Section

50. Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

51. HEC-RAS: Background Hydraulic model of the U.S. Army Corps of Engineers Input = cross-section geometry and flow rates Output = flood water elevations Cross-Section Schematic

52. Points describe channel and floodway geometry Bank station locations Water surface elevations and floodplain boundaries HEC-RAS: Cross-Section Description

53. HEC-RAS: Output Text File Graphical

54. Data translation from HEC-RAS text file to dbase table Bank and floodplain boundaries measured from stream centerline HEC-RAS: Data Translation

55. Digital orthophotograph and road coverage used as a base map User digitizes stream with mouse Boundary points define the RAS stream Digital Stream Mapping

56. Floodplain Mapping: Plan View

57. 3D Terrain Modeling: Ultimate Goal

58. For more information about GIS and Hydrology, see http://www.ce.utexas.edu/prof/maidment To obtain CRWR-PrePro to link ArcView with HEC-HMS, see http://www.ce.utexas.edu/prof/olivera/prepro/prepro.htm To take an online spatial hydrology course, see http://campus.esri.com/campus/home/home.cfm Web Links