Thursday, February 12, 2009

Breach Progression-Linear or Sine Wave?


Written by Chris Goodell, P.E., D. WRE | WEST Consultants
Copyright © RASModel.com. 2009. All rights reserved.

I get this question a lot. Do I use a linear or sine wave dam breach progression? The concept of the sine wave breach progression is that the breach will initially grow at a slow rate (when the breach just begins to form, not a lot of head on the breach), then it will speed up as velocities and shear stress picks up through the breach. Then it will slow down again at the end of the breach as the water level in the reservoir reduces to a small amount over the breach invert.
There's no real research out there that I know of that addresses this. The way I look at it is if my reservoir draws down with my breach (slow breach/small reservoir case), then the sine wave progression makes more sense to me. If my reservoir remains high as the breach is forming (fast breach/large reservoir case), then the linear progression makes more sense to me (actually a combination of the two makes the most sense to me in this case-this can be done by manually chaning the values in the table on the side to start out as a sine wave and then transform into linear). In all honesty, I usually incorporate the breach progression into my sensitivity analysis, and eventually go with the more conservative of the two.


2 comments:

  1. Hi,

    I have a question, after you create the junction, the river is divided, we consider that the junction was made ​​between station 1 and 2, how do I create a culvert between station 3 and 0, Since the section is divided?

    thank you.

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    Replies
    1. Unfortunately, you cannot have a culvert pass through a junction. You might explore using a lateral structure with a culvert while making your split reach your primary reach. No guarantees, but perhaps this can help with your problem.

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