by David M. Beekman and Vito A. Cimino

Experience of Flood Analysis in the Ohio River Basin Using

ArcView GIS for HEC-RAS Flow Computation

Co-authored by Dr. Tiao Chang

Department of Civil Engineering, Ohio University

Terri Dawson, Coy Miller, Jerry Web US Army Corps of Engineers, Water Resources Engineering

Objectives

• Convert existing HEC-2 data to HEC-RAS

• Geo-Reference data using ArcView GIS

• Present Inundation Mapping

• Generate channel cross sections using HEC-2 data

Project Location

#Columbus

.-, 71

.-,70

Delaware Co.

Franklin Co.

.-,71

Alum Creek

What’s Required?

• Existing HEC-2 data for desired reach

• HEC-RAS

• ArcView GIS

• USGS 1:24,000 DLG data

Data

Software

Procedure Outline• Spatial Data Management

• Cross Section Generation

• Pre-processing

• Hydraulic Flow Computations

• Post-processing

• Final Inundation Map Production

• Final DEM Production

Spatial Data Management

• Download USGS 1:24,000 DLGs– Hypsography

– Hydrography

– Roads

• Convert to shapefiles in ArcView

• Delineate stream centerline and banks

Cross Section Generation

• Analysis of HEC-2 Data– Cross section lengths

– Distance between

adjacent cross sections

– Cross section elevations

Cross Section Generation (cont.)

• Application of ArcView – Constructed manually

– Based on topography and cross section survey data

– Cross section stationing and distance calculations

(use of AVRAS 2.2 – ArcView extension)

Geo-Referenced Cross Sections

Pre-processing• Preparation of temporary terrain TIN

– USGS hypsography DLGs

• Implement AV-RAS options in ArcView (use of AVRAS 2.2 – ArcView extension)

Pre-processing (cont.)

• Select AV-RAS theme setup– TIN

– Cross sections

– Centerline

– Banks

– Flow path

Pre-processing (cont.)

• Complete remaining AV-RAS options

• Generate *.geo file– Import file for HEC-RAS

– Consists of ArcView geometric data

•HEC-2 X-sections •Preprocessed X-sections

51

5049

4745.5

43.54241.5

4039.537.5

35.534

32.531

29.5

27.5

2625

24.5 24.424.222.222

20

18.5

16151413

11.510

98

6

43.5

2.51

0.1

16850.6316346.85

15858.7615537.47

15071.5114729.19

14230.1613845.8813440.95

12857.92

12400.68

11684.1611362.2811038.61

10665.6610388.93

10025.789491.444

8899.6608529.983

7911.9317588.6816885.093

6199.7885938.369

5483.6934765.771

4152.2583908.7113597.673

2849.026

2171.851

1524.416995.995 613.603

Hydraulic Flow Computation

• Adjust GIS geometry file according to HEC-2 data in HEC-RAS– Ground elevations

– Cross section lengths

• Adding parameters– Manning’s‘n’ values

– Contraction/Expansion coefficients

– Bridges/Piers

– Steady flow data

Hydraulic Flow Computation

• Model verification

• Run water surface profile computations

• Generate *.gis file (HEC-RAS export file)

• Run Avenue script to export cross sections into ArcView– Cross section and point elevation shapefiles generated

– Based on HEC-RAS geometry data

• Point elevation data (original HEC-2 data)

• Topographical elevation data (USGS data)

• Final DEM produced

Final DEM Production

Final DEM

Post-processing

• Implement RAS-AV options in ArcView (use of AVRAS 2.2 – ArcView extension)

• Select RAS-AV theme setup– HEC-RAS *.gis export file

– Creation of output directory

– Terrain TIN

– Rasterization cell

Post-processing (cont.)

Post-processing (cont.)

• Complete remaining RAS-AV options

• Select desired water surface elevations

• Floodplain delineation

Alum Creek Floodplain4,200 cfs6,500 cfs8,100 cfs13,600 cfs

4,200 cfs

Final Inundation Mapping

6,500 cfs

Final Inundation Mapping

8,100 cfs

Final Inundation Mapping

13,600 cfs

Final Inundation Mapping

Conclusions• Converted HEC-2 data to HEC-RAS

• Created cross sections to geographically reference HEC-2 data with ArcView GIS

• Performed hydraulic flow analysis with HEC-RAS

• Presented Inundation Mapping for floodplain delineation

Ohio University

Acknowledgements

U.S. Army Corps of Engineers, Huntington District

Questions?