Map-Based%20Flood%20Hydrology%20and%20Hydraulics

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Map-Based Flood Hydrology and Hydraulics

• David R. Maidment
• Jan 10, 1998

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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

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Map-Based Hydrology and Hydraulics
ArcView Input Data DEM
ArcView Flood plain maps
CRWR-PrePro
HEC-RAS Water surface profiles
HEC-HMS Flood discharge
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Austin Digital Elevation Model
Waller Creek
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Austin Watersheds
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CRWR-PrePro
Digital Elevation Model Stream Map
ArcView-based preprocessor for HEC-Hydrologic
Modeling System (HEC-HMS)
Control point locations
HMS Basin File
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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

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Study Region in West Austin
Hog Pen Ck
4 km
4 km
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Watershed Delineation by Hand Digitizing
Watershed divide
Outlet
Drainage direction
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30 Meter MeshStandard for 124,000 Scale Maps
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DEM Elevations
720
720
Contours
740
720
700
680
680
700
720
740
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DEM Elevations
Contours
700
680
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Eight Direction Pour Point Model
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Direction of Steepest Descent
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1
67
56
49
53
44
37
58
55
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Slope
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Flow Direction Grid
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Austin West 30 Meter DEMElevations in meters
ftp//ftp.tnris.state.tx.us/tnris/demA.html
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Flow Direction Grid
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Grid Network
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Flow Accumulation Grid
0
0
0
0
0
0
0
0
0
0
0
3
2
2
0
0
3
2
0
2
0
0
1
0
0
11
0
1
0
11
0
0
0
1
15
0
0
1
0
15
1
0
2
24
5
2
5
0
1
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Link to Grid calculator
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Flow Accumulation gt 5 Cell Threshold
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Stream Network for 5 cell Threshold Drainage Area
0
0
0
0
0
0
3
2
0
2
0
0
1
0
11
0
0
1
0
15
2
5
0
1
24
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Streams with 200 cell Threshold(gt18 hectares or
13.5 acres drainage area)
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Watershed Outlet
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Watershed Draining to This Outlet
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Watershed and Drainage Paths Delineated from 30m
DEM
Automated method is more consistent than hand
delineation
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DEM Data Sources for Texas

• Digital terrain models with 2 or 4 contours
  built from aerial photogrammetry
• 10m DE-DEMs, from 124,000 scale maps with
  drainage enforcement (experimental)
• 30m DEMs from 124,000 scale maps
• 1 seamless DEM of Texas (March, 1999)
• 3" (100m) DEMs from 1250,000 scale maps (current
  state-wide coverage)

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DEM Watersheds for Austin
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Selected Watersheds and Streams
Mansfield Dam
Colorado River
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HMS Schematic Prepared with CRWR-PrePro
Mansfield Dam
Colorado River
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HMS Basin File
Basin file is a text description of all
hydrologic elements
155
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87
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Subbasin
Reach
Junction
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HMS Model of the Austin Region
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(No Transcript)
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Maps Served on the Web
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Design Precipitation Input
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HMS Control File
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HMS Results
Watershed 155
Junction 44
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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

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Regional flood analysis in Houston
Study region
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Study Region in West HoustonMaps Developed using
CRWR-Prepro by Seth Ahrens
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Nexrad Rainfall for Storm of Oct 1994
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Discharge in Buffalo Bayou at KatyOctober, 1994
storm
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Calibrated Flow with HEC-HMS
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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

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Waller Creek DEM
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Waller Creek Watershed Outlets
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Waller Creek HMS Model
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Flood Plain Mapping
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Connecting HMS and RAS
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Discharge at a Particular Cross-Section
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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

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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
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HEC-RAS Cross-Section Description

• Points describe channel and floodway geometry
• Bank station locations
• Water surface elevations and floodplain
  boundaries

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HEC-RAS Output

• Graphical

• Text File

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HEC-RAS Data Translation

• Data translation from HEC-RAS text file to dbase
  table
• Bank and floodplain boundaries measured from
  stream centerline

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Digital Stream Mapping

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

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Floodplain Mapping Plan View
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3D Terrain Modeling Ultimate Goal
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For more information about GIS and Hydrology,
seehttp//www.ce.utexas.edu/prof/maidmentTo
obtain CRWR-PrePro to link ArcView with HEC-HMS,
seehttp//www.ce.utexas.edu/prof/olivera/prepro/p
repro.htmTo take an online spatial hydrology
course, seehttp//campus.esri.com/campus/home/hom
e.cfm
Web Links