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Application of HEC-HMS for Hydrologic Studies

Application of HEC-HMS for Hydrologic Studies. Texas A&M University Department of Civil Engineering CVEN689 – Applications of GIS in CE Instructor: Dr. Francisco Olivera Logan Burton 3/14/03. Outline. HMS and GIS Project Overview Challenges Solutions Methodology Results. HEC-HMS.

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Application of HEC-HMS for Hydrologic Studies

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  1. Application of HEC-HMS for Hydrologic Studies Texas A&M University Department of Civil Engineering CVEN689 – Applications of GIS in CE Instructor: Dr. Francisco Olivera Logan Burton 3/14/03

  2. Outline • HMS and GIS • Project Overview • Challenges • Solutions • Methodology • Results

  3. HEC-HMS • HMS Hydrologic Modeling System • Developed by the U.S. Army Corp of Engineers • A numerical model that can help predict runoff volumes, peak flows, and timing of flows by simulating the behaviors of the watersheds, channels, and reservoirs.

  4. HEC-HMS Advantages • Can be applied to a variety of watersheds with different shapes, sizes and characteristics • Graphical User Interface makes the program user friendly • Software is public domain - Can be downloaded from HEC website at no cost

  5. HMS Applications • Urban Flooding This project • Flood Frequencies • Flood-loss reduction • Flood warning systems • Reservoir Design • Other Environmental studies *From HEC-HMS Applications Guide, Dec. 2002

  6. Advantages of Using GIS in Hydrologic Studies • Effective and efficient delineation of watersheds and streams • Quick extraction of watershed and stream parameters • DEMs can define the drainage basin boundaries

  7. Urban Flooding • What is an Urban Flooding Study? A hydrologic study in an urban area to analyze or predict flooding problems. Common Characteristics • Short response times • Drainage systems in place • Development plays large role watershed behavior

  8. Scope of Urban Flooding • Model and analyze existing basin • Edit model to simulate urbanization • Analyze new model to help predict impact of future development

  9. Salado Creek Basin • Location: Bexar County San Antonio, TX San Antonio

  10. Urbanized Watershed

  11. Salado Creek

  12. Required Information • Peak Flows • Runoff Volume • Flow Timing • Peak Stage* • Floodplain Delineation* *HEC-RAS is used to calculate these All of this information is required for current and future development

  13. Required Data for Analysis • DEM (30 meter) • NHD files • USGS Gauging Stations • HUC boundaries Optional: DRG topographic map

  14. GIS Challenges • Gathering Data – different sources

  15. GIS challenges • Managing and Organizing Data - Different Sources = Different Projections - Very Important to keep the metadata with the downloaded files • These problems can be easily solved by using the available tools and extensions

  16. Extensions and Tools • CRWR-Vector* - project vector data • ArcInfo – project raster data • CRWR-Raster* - merge grids • CRWR-PrePro* - data pre-processor • HEC-GeoHMS could have been used in place of PrePro *Programs written by Dr. Francisco Olivera

  17. Projecting Shapefiles • CRWR-Vector is used to project shapefiles (points, lines, polygons) • Use the project tool in the pull down menu

  18. CRWR-PrePro • Can be downloaded from Dr. Olivera’s website • Predecessor to GeoHMS

  19. HEC-GeoHMS • Can be downloaded from HEC website • Menu is very similar to CRWR-Prepro

  20. Methodology • Projected all data to UTM27 – Zone 14 • Ran CRWR-PrePro to delineate watershed - Problem appeared

  21. Problem • PrePro requires that stream lengths be greater than 1 cell • Cell size is 28.85 m

  22. Solution: Step 1 • Add point theme

  23. Step 2 • Add “Elevation” Field to attribute table

  24. Step 3 • Convert the point theme to a grid

  25. Step 4 • Merge original DEM to new grid using CRWR-Raster

  26. Step 5 • Re-run CRWR-PrePro with fixed grid

  27. Process Data • Calculate Attributes • HMS Schematic

  28. HMS Components • Basin Model • Meteorological Model • Control Specifications

  29. Basin Model • Imported from ArcView

  30. Imported Basin Model

  31. Basin Characteristics • Initial/Constant Loss Rate • Initial loss = 0.39 in • Constant loss = 0.20 in - From local soil parameters • Before Development: Northern basins – 10-25% imperviousness Southern basins - 75% imperviousness - HMS Reference Manual

  32. Meteorological Model Input from TxDot Hydraulic Manual for Bexar County

  33. Control Specifications • Rainstorm of October 17-18, 1998 was used

  34. Calibration USGS Fact Sheet FS-147-99

  35. Calibration

  36. Effects of Urbanization • After Development: Entire basin model = 75% imperviousness

  37. Results Undeveloped Basin Developed Basin • Development increased flow 10,000 cfs (16%) at this gauging station

  38. Floodplains • Input channel geometry and roughness data into HEC-RAS • Import peak flows from developed basin into HEC-RAS to calculate water surface elevations and floodplains

  39. Questions? SaladoCreek

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