Application of HEC-HMS for Hydrologic Studies

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Application of HEC-HMS for Hydrologic Studies

• Texas AM University
• Department of Civil Engineering
• CVEN689 Applications of GIS in CE
• Instructor Dr. Francisco Olivera
• Logan Burton
• 3/14/03

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Outline

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

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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.

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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

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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

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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

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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

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Scope of Urban Flooding

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

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Salado Creek Basin

• Location
• Bexar County
• San Antonio, TX

San Antonio
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Urbanized Watershed
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Salado Creek
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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
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Required Data for Analysis

• DEM (30 meter)
• NHD files
• USGS Gauging Stations
• HUC boundaries
• Optional DRG topographic map

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GIS Challenges

• Gathering Data different sources

Type of Data Source
DEM TNRIS http//www.tnris.state.tx.us/digital.htm
NHD files USGS http//nhd.usgs.gov/
Gauging Stations USGS http//water.usgs.gov/lookup/getspatial?realstx
Huc Boundaries USGS http//water.usgs.gov/GIS/huc.html
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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

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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

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Projecting Shapefiles

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

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CRWR-PrePro

• Can be downloaded from Dr. Oliveras website
• Predecessor to GeoHMS

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HEC-GeoHMS

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

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Methodology

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

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Problem

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

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Solution Step 1

• Add point theme

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Step 2

• Add Elevation Field to attribute table

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Step 3

• Convert the point theme to a grid

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Step 4

• Merge original DEM to new grid using CRWR-Raster

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Step 5

• Re-run CRWR-PrePro with fixed grid

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Process Data

• Calculate Attributes
• HMS Schematic

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HMS Components

• Basin Model
• Meteorological Model
• Control Specifications

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Basin Model

• Imported from ArcView

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Imported Basin Model
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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

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Meteorological Model
Input from TxDot Hydraulic Manual for Bexar County
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Control Specifications

• Rainstorm of October 17-18, 1998 was used

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Calibration
USGS Fact Sheet FS-147-99
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Calibration
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Effects of Urbanization

• After Development
• Entire basin model 75 imperviousness

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Results

• Development increased flow 10,000 cfs (16) at
  this gauging station

Undeveloped Basin
Developed Basin
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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

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Questions?
Salado Creek