Custom geographic projections and HEC-RAS

This is my research report on using custom geographic projections with HEC-RAS 5.0.7. All my tests were based on the NAD83 AZ State Plane Central Zone 0202 International Feet (AZ83-CIF) projection.

Using HEC-RAS 2D area breaklines to improve modeling

HEC-RAS 2D area breaklines are a great way to force cell faces to follow a terrain ridge or crest hinge (top of slope) line. Without them, you are never quite sure whether flow is going over or through high points in your terrain.

Best practices for HEC-RAS 1D modeling with AutoCAD Civil 3D

Best practices for HEC-RAS 1D modeling with AutoCAD Civil 3D

Best practices for HEC-RAS 2D modeling with AutoCAD Civil 3D

I've had enough experience now using AutoCAD Civil 3D and HEC-RAS for 2D flow modeling in Maricopa County Arizona to share a list of best practices. It's only a small beginning, but it's something. Enjoy.

HEC-RAS 2D Land Cover from AutoCAD

I had a bit of trouble getting a Land Cover map from AutoCAD to HEC-RAS today. I made a map, but HEC-RAS kept telling me the file "has 0 features". It turns out I needed to set the project projection to the projection exported from AutoCAD with the Land Cover map.

How Roughness and Loss Coefficients are Applied to Reaches in HEC-RAS

It's really hard to find a clear explanation of how roughness and loss coefficients are applied to reaches in HEC-RAS.  I ran extensive scenario testing today and here are my results.

HEC-RAS 2D Area Stability

I did some testing on stability and accuracy for a HEC-RAS 2D only model.

Exporting a HEC-1 Hydrograph for HEC-RAS Unsteady Flow

We are going to export a HEC-1 hydrograph to a DSS file to use in HEC-RAS unsteady flow modeling.  This will be useful for us to do 2D flow modeling in HEC-RAS

HEC-RAS Reach Lengths and Civil 3D Export

When you export geometry from Civil 3D to HEC-RAS using ExportHECRAS, of course you wonder exactly what reach lengths Civil 3D is exporting, since your friction losses are proportional to those lengths,  Well.  Wonder no more.  As of Civil 3D 2016, the reach lengths are exported like this:

Importing From HEC-RAS to Civil 3D using the IMPORTHECRAS command

When you export from HEC-RAS (File, Export GIS DATA) you must check the Water Surface Extents checkbox.

The "cross section" lines that come in are not really the cross sections.  They each represent a straight line from the left inundation limit to the right inundation limit.

Maybe it's time to write a LISP routine.

How to delineate flood limits in Civil 3D using HEC-RAS 5

With the release of HEC-RAS 5, we now have between Civil 3D and HEC-RAS all the tools we need to send our terrain and stream geometry from Civil 3D to HEC-RAS, delineate flood limits in HEC-RAS, and send the inundation limits back to Civil 3D.

Simplest method to export geometry from Civil 3D and import to HEC-RAS

The Civil 3D Output ribbon provides an Export to HEC-RAS button, and HEC-RAS provides an Import Geometry Data tool.  But getting river direction, river stations, banks, and cross section stations transferred right is not as easy or as obvious as it could be.  This is a method to export as completely as possible from Civil 3D and use as few fixes as possible in HEC-RAS to fix the data.