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 HMS and GIS Project Overview Project Overview Challenges Challenges Solutions Solutions Methodology Methodology Results Results

HEC-HMS HMS Hydrologic Modeling System HMS Hydrologic Modeling System Developed by the U.S. Army Corp of Engineers 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. 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.

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

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

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

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

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

Salado Creek Basin Location: Location: Bexar County San Antonio, TX San Antonio

Urbanized Watershed

Salado Creek

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

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

GIS Challenges Gathering Data – different sources Gathering Data – different sources Type of Data Source DEMTNRIShttp:// NHD files USGShttp://nhd.usgs.gov/ Gauging Stations USGS alstx Huc Boundaries USGShttp://water.usgs.gov/GIS/huc.html

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

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

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

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

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

Methodology 1. Projected all data to UTM27 – Zone Ran CRWR-PrePro to delineate watershed - Problem appeared

Problem PrePro requires that stream lengths be greater than 1 cell PrePro requires that stream lengths be greater than 1 cell Cell size is m Cell size is m

Solution: Step 1 Add point theme Add point theme

Step 2 Add “Elevation” Field to attribute table Add “Elevation” Field to attribute table

Step 3 Convert the point theme to a grid Convert the point theme to a grid

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

Step 5 Re-run CRWR-PrePro with fixed grid Re-run CRWR-PrePro with fixed grid

Process Data Calculate Attributes Calculate Attributes HMS Schematic HMS Schematic

HMS Components Basin Model Basin Model Meteorological Model Meteorological Model Control Specifications Control Specifications

Basin Model Imported from ArcView Imported from ArcView

Imported Basin Model

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

Meteorological Model Input from TxDot Hydraulic Manual for Bexar County

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

Calibration USGS Fact Sheet FS

Calibration

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

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

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

Questions? Salado Creek