Suppose you have two separate HEC-RAS rivers and wish to combine them. There is no “combine two rivers” option in HEC-RAS, but it can be done using the Move Points/Objects option. Take the very simple reach presented below: I wish to combine the Upper Tualatin with the Clackamas reach of the Willamette River. In the […]
The last post on XS interpolation gave an overview for reasons cross section interpolation may be necessary and a detailed description of Interpolation Option A: “Within a Reach”. http://hecrasmodel.blogspot.com/2014/05/exploring-hec-ras-xs-interpolation.html This post will cover Option B: “Between 2 XS’s”. Between 2 XS’s simply means HEC-RAS will interpolate cross sections ONLY between two selected “non-interpolated” cross sections. […]
Ahead of the wide-scale implementation of the 2-dimensional (2-D) modeling module in HEC-RAS, I wanted to share a quick tip that will be useful for editing your 1-dimensional (1-D) HEC-RAS model to prepare to couple your 1-D channel with a 2-D overbank area. It’s common to have a cross section with a well-defined channel and […]
As RAS model development is done more and more through GIS, using the HEC-GeoRAS extension, cross section point filtering is becoming a standard part of the HEC-RAS model development exercise. It’s not too uncommon for a model created in GIS to have multiple hundreds of cross section station elevation points. This is normally not a […]
I’m a big proponent of checking flow consistency in your results. Anyone who has taken a RAS class from me has heard me go on about Standard Table 2 and the benefits of maintaining a consistent distribution of flow not only between sub sections (left overbank, main channel, right overbank) in a cross section, but […]
What are the implications of having a cross section that is too short and doesn’t extend all the way out to the highest computed water surface elevation? Does it affect the results? Take this cross section for example. It is missing much of the left overbank (presumably). Image courtesy of Adam Bohnoff First of all, […]
Cross sections must be perpendicular to the flow lines at all locations. And they cannot intersect with each other. That is why it is common to see cross sections snap at different angles outside the main channel (we call this doglegging). The trick is to keep them from intersecting, while also staying perpendicular to flow […]
Written by Chris Goodell, P.E., D. WRE | WEST ConsultantsCopyright © RASModel.com. 2010. All rights reserved.Here’s a classic case for interpolation of cross sections in a RAS model. Notice the drop in water surface to near critical depth at the grade break. Then, at the next cross section upstream of the break, RAS seems to […]