Application of HEC HMS for Urban Flooding Studies CEProfs by renata.vivien


									Application of HEC-
HMS for Hydrologic
         Texas A&M University
    Department of Civil Engineering
  CVEN689 – Applications of GIS in CE
    Instructor: Dr. Francisco Olivera
             Logan Burton
n   HMS and GIS
n   Project Overview
n   Challenges
n   Solutions
n   Methodology
n   Results
n   HMS        Hydrologic Modeling System
n   Developed by the U.S. Army Corp of
n   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
n   Can be applied to a variety of watersheds
    with different shapes, sizes and
n   Graphical User Interface makes the
    program user friendly
n   Software is public domain
    - Can be downloaded from HEC website at
    no cost
                HMS Applications
n   Urban Flooding        This project
n   Flood Frequencies
n   Flood-loss reduction
n   Flood warning systems
n   Reservoir Design
n   Other Environmental studies

*From HEC-HMS Applications Guide, Dec. 2002
     Advantages of Using GIS in
        Hydrologic Studies

n   Effective and efficient delineation of
    watersheds and streams
n   Quick extraction of watershed and stream
n   DEMs can define the drainage basin
               Urban Flooding
n       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
     Scope of Urban Flooding
n   Model and analyze existing basin
n   Edit model to simulate urbanization
n   Analyze new model to help predict impact
    of future development
         Salado Creek Basin
n   Location:
    Bexar County
    San Antonio, TX
Urbanized Watershed
Salado Creek
        Required Information
n   Peak Flows
n   Runoff Volume                     All of this information is
                                      required for current and
n   Flow Timing                       future development

n   Peak Stage*
n   Floodplain Delineation*

*HEC-RAS is used to calculate these
    Required Data for Analysis
n   DEM (30 meter)
n   NHD files
n   USGS Gauging Stations
n   HUC boundaries

Optional: DRG topographic map
                 GIS Challenges
n   Gathering Data – different sources

Type of Data               Source
DEM                        TNRIS
NHD files                  USGS
Gauging Stations           USGS
Huc Boundaries             USGS
             GIS challenges
n Managing and Organizing Data
- Different Sources = Different Projections
- Very Important to keep the metadata with the
  downloaded files

n   These problems can be easily solved by using
    the available tools and extensions
          Extensions and Tools
n   CRWR-Vector* - project vector data
n   ArcInfo – project raster data
n   CRWR-Raster* - merge grids
n   CRWR-PrePro* - data pre-processor

n   HEC-GeoHMS could have been used in
    place of PrePro

*Programs written by Dr. Francisco Olivera
        Projecting Shapefiles
n   CRWR-Vector is used to project shapefiles
    (points, lines, polygons)
n   Use the project tool in the pull down menu
n   Can be downloaded
    from Dr. Olivera’s
n   Predecessor to
n   Can be downloaded
    from HEC website
n   Menu is very similar
    to CRWR-Prepro
n   Projected all data to UTM27 – Zone 14
n   Ran CRWR-PrePro to delineate
    - Problem appeared
n   PrePro requires that stream lengths be greater than 1 cell
n   Cell size is 28.85 m
            Solution: Step 1
n   Add point theme
                      Step 2
n   Add “Elevation” Field to attribute table
                     Step 3
n   Convert the point theme to a grid
                    Step 4
n   Merge original DEM to new grid using CRWR-
                    Step 5
n   Re-run CRWR-PrePro with fixed grid
             Process Data
n   Calculate
n   HMS Schematic
       HMS Components
•   Basin Model
•   Meteorological Model
•   Control Specifications
               Basin Model
n   Imported from ArcView
Imported Basin Model
         Basin Characteristics
n   Initial/Constant Loss Rate
    •  Initial loss = 0.39 in
    • Constant loss = 0.20 in

    - From local soil parameters

n   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
n   Rainstorm of October 17-18, 1998 was used
Sheet FS-
      Effects of Urbanization
n   After Development:
    Entire basin model = 75% imperviousness
n   Development increased flow 10,000 cfs (16%) at
    this gauging station
Undeveloped Basin          Developed Basin
n   Input channel geometry and roughness
    data into HEC-RAS

n   Import peak flows from developed basin
    into HEC-RAS to calculate water surface
    elevations and floodplains
Salado Creek

To top