Methodology - Response of Flood Events to Land Use and Climate Change - page 72

Start an ArcGIS project

1. Stream center line

2. Cross sections cut lines

3. Ras layers creation

GIS data developmnet

4. Attribute cross section cut lines

5. Extract elevation data for

RAS layers

Generate RAS GIS
import file

1. Create new HEC RAS project

2. Import RAS GIS import file

Run HEC RAS 3. Compute HEC RAS results

4. Review results for hydraulic

correctness

Enough cross
sections?

No

Yes

Generate RAS GIS Export file
.RASExport.sdf

1. Convert .RAS Export.sdf to XML

2. Import RAS GIS export file

RAS results processing
RAS Mapping

3. Inundation mapping

4. Additional mapping such as

velocity and depth of water

Correct
inundation area

No

Reduce grid
cell size

Yes

Detailed floodplain
analysis

Enough cross
sections?

Sufficient map
details?

No Yes

No

Fig. 3.8 The process modeling in HEC-GeoRAS and HEC-RAS (HEC-RAS manual [ 64 ])

V u
gL c

p

FR ¼ ð 3 : 24 Þ

where,
V u = upstream velocity and L c = characteristics length for the channel flow.
The dimensionless Froude number (Fr) is applied to characterize the flow
regime, where:

• Froude Number (Fr) \ 1 represents subcritical flow
• Froude Number (Fr) [ 1 represents supercritical flow
• Froude Number (Fr) = 1 represents critical flow (Fig. 3.9 )