Map-Based Flood Hydrology and Hydraulics

David R. Maidment Jan 10, 1998

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

Map-Based Hydrology and Hydraulics

ArcViewInput Data

DEM

HEC-HMSFlood

discharge

HEC-RASWatersurfaceprofiles

ArcViewFlood

plain maps

CRWR-PrePro

Austin Digital Elevation Model

Waller Creek

Austin Watersheds

CRWR-PrePro

ArcView-based preprocessorfor HEC-Hydrologic ModelingSystem (HEC-HMS)

Digital Elevation ModelStream Map

HMS Basin File

Control point locations

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

Study Region in West Austin

Hog Pen Ck

4 km

4 km

Watershed Delineation by Hand Digitizing

Watershed divide

Drainage direction Outlet

30 Meter MeshStandard for 1:24,000 Scale Maps

DEM Elevations

Contours

720

700

680

740

680700720740

720 720

DEM Elevations Contours

700

680

32

16

8

64

4

128

1

2

Eight Direction Pour Point Model

67 56 49

53 44 37

58 55 22

1

67 56 49

53 44 37

58 55 22

1

26.162

4467

14

1

5367

Slope:

Direction of Steepest Descent

2 2 4 4 8

1 2 16

1 2 4 8 4

128 1 2 4 8

2 1 4 4 4

11

Flow Direction Grid

Austin West 30 Meter DEMElevations in meters

ftp://ftp.tnris.state.tx.us/tnris/demA.html

Flow Direction Grid

32

16

8

64

4

128

1

2

Grid Network

0 0 000

0

0

0

0

0

0

0

0

03 2 2

11 1

1 152 5

24 1

0 0 00 0

0

0

0

0

0

0

0

0

0

3 2 2

11 1

1

12

15

245

Flow Accumulation Grid

Link to Grid calculator

0 0 00 0

0

0

0

0

0

0

0

0

0

3 2 2

11 1

1

12

15

245

Flow Accumulation > 5 Cell Threshold

Stream Network for 5 cell Threshold Drainage Area

0 0 000

0

0

0

0

0

0

0

0

03 2 2

111

115

2 5

241

Streams with 200 cell Threshold(>18 hectares or 13.5 acres drainage area)

Watershed Outlet

Watershed Draining to This Outlet

Watershed and Drainage Paths Delineated from 30m DEM

Automated method is more consistent than hand delineation

DEM Data Sources for Texas

• Digital terrain models with 2’ or 4’ contours built from aerial photogrammetry

• 10m DE-DEMs, from 1:24,000 scale maps with drainage enforcement (experimental)

• 30m DEMs from 1:24,000 scale maps

• 1” seamless DEM of Texas (March, 1999)

• 3" (100m) DEMs from 1:250,000 scale maps (current state-wide coverage)

DEM Watersheds for Austin

Selected Watersheds and Streams

Mansfield Dam

ColoradoRiver

HMS Schematic Prepared with CRWR-PrePro

Mansfield Dam

ColoradoRiver

HMS Basin FileBasin file is a textdescription of all hydrologic elements

15533

8739Subbasin

Junction

Reach

HMS Model of the Austin Region

Maps Served on the Web

Design Precipitation Input

HMS Control File

HMS Results

Watershed 155 Junction 44

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

Regional flood analysis in Houston

Study region

Study Region in West HoustonMaps Developed using CRWR-Prepro by Seth Ahrens

Nexrad Rainfall for Storm of Oct 1994

Discharge in Buffalo Bayou at KatyOctober, 1994 storm

Calibrated Flow with HEC-HMS

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

Waller Creek DEM

Waller Creek Watershed Outlets

Waller Creek HMS Model

Flood Plain Mapping

Connecting HMS and RAS

Discharge at a Particular Cross-Section

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

HEC-RAS: BackgroundHydraulic model of the U.S. Army Corps of Engineers

Input = cross-section geometry and flow rates

Output = flood water elevations

Floodway Floodway

Left Bank Station

Flood Water Surface

Right Bank Station

Normal Water Surface

Main Channel

Cross-Section Schematic

Points describe channel and floodway geometry

Bank station locations

Water surface elevations and floodplain boundaries

HEC-RAS: Cross-Section Description

HEC-RAS: OutputText FileGraphical

Data translation from HEC-RAS text file to dbase table

Bank and floodplain boundaries measured from stream centerline

HEC-RAS: Data Translation

Digital orthophotograph and road coverage used as a base map

User digitizes stream with mouse

Boundary points define the RAS stream

Digital Stream Mapping

Floodplain Mapping: Plan View

3D Terrain Modeling: Ultimate Goal

For more information about GIS and Hydrology, see

http://www.ce.utexas.edu/prof/maidment

To obtain CRWR-PrePro to link ArcView with HEC-HMS, see

http://www.ce.utexas.edu/prof/olivera/prepro/prepro.htm

To take an online spatial hydrology course, see

http://campus.esri.com/campus/home/home.cfm

Web Links