Hydrologic%20Cycle

1
Hydrologic Cycle
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Hydrologic Cycle Processes
Processes
Precipitation Evaporation Surface
Runoff Groundwater Recharge Baseflow
Surface Water
3
Map-Based Hydrology and Hydraulics
ArcView Input Data DEM
ArcView Flood plain maps
CRWR-PrePro
AvRAS
HEC-RAS Water surface profiles
HEC-HMS Flood discharge
4
GIS-Based Flood Modeling

• Terrain analysis using Digital Elevation Models
• Flood hydrology model for the Austin region
• Creating flood plain maps for Waller Creek
• Real time flood emergency management

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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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Eight Direction Pour Point Model
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DEM Elevations
Contours
700
680
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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
24
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Flow Accumulation gt 5 Cell Threshold
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Streams with 200 cell Threshold(gt18 hectares or
13.5 acres drainage area)
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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

• 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)
• 30 (1km) DEMs global coverage

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Coverage of DEMs
1 seamless DEM
3" (100m) DEM
1º
30m DEM
7.5
7.5
1º
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Cell Size
30m (1)
100m (3)
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GIS-Based Flood Modeling

• Terrain analysis using Digital Elevation Models
• Flood hydrology model for the Austin region
• Creating flood plain maps for Waller Creek
• Real time flood emergency management

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Map-Based Hydrology and Hydraulics
ArcView Input Data DEM
ArcView Flood plain maps
CRWR-PrePro
AvRAS
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
Soil and Land Use Maps
HMS Basin File
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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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• SCS Runoff Curve Number method determines the
  direct runoff from storm rainfall in small
  watersheds.
• Curve number (CN) is a function of hydrologic
  soil group and land use.

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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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Design Precipitation Input
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Maps Served on the Web
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Nexrad Rainfall for Storm of Oct 1994
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HMS Results
Watershed 155
Junction 44
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GIS-Based Flood Modeling

• Terrain analysis using Digital Elevation Models
• Flood hydrology model for the Austin region
• Creating flood plain maps for Waller Creek
• Real time flood emergency management

38
Map-Based Hydrology and Hydraulics
ArcView Input Data DEM
ArcView Flood plain maps
CRWR-PrePro
AvRAS
HEC-RAS Water surface profiles
HEC-HMS Flood discharge
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Waller Creek DEM
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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
ArcView Input Data DEM
ArcView Flood plain maps
CRWR-PrePro
AvRAS
HEC-RAS Water surface profiles
HEC-HMS Flood discharge
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HEC-RAS Background

• River Analysis System 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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GIS-Based Flood Modeling

• Terrain analysis using Digital Elevation Models
• Flood hydrology model for the Austin region
• Creating flood plain maps for Waller Creek
• Real time flood emergency management

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Real-time flood emergency mapping
Nexrad radar rainfall input
Real time
Precomputed flood map library
Offline
Flood hydrology analysis system