HEC-GEORAS on a small stream in North Branch,

Clear CreekZhihao Wang

Sep 2011

HEC-RAS◦perform one-dimensional steady and unsteady

flow river hydraulics calculations

HEC-GeoRAS◦pre- and/or post-process GIS data and HEC-RAS

results for flood inundation mapping using ArcGIS

HEC-GeoRAS creates a file of geometric data for import into HEC-RAS, and enables viewing of exported results from RAS.

Pre-process

Post-process

TIN of part of the North branch, Clear Creek

HEC-GeoRAS requires a DTM (digital terrain model) in the form of TIN or GRID.

30mDEM

8mDEM, 23m z tolerance

8mDEM, 1m z tolerance

Flow rate generated by GeoWEPP (referred to as runoff)

Create RAS layers: ◦Stream centerlines, Banks, Flow paths, Cross

section cutlines, other optional layers◦By creating empty layers and digitize manually

Stream centerlines

Banks

Flow paths

Cross section cutlines

Assign attributes to:◦Stream centerlines (names, topology, length)◦Flow paths (left/right/center)◦Cross section cutlines (river/reach name, bank

stations, elevation…)

Manning’s value

Extract GIS data HEC-RAS geometric data

Cross section view in HEC-RAS

Set up the flow rate data

2-year scenario simulation results

Conventional tillage

Conservation tillage

No tillage