Encroachment in Hec_Ras 3

[sujanshakya]

I had a FEMA model with encroachment analysis. I added few surveyed cross-sections into this model. And, when I tried to run the encroached model, the 'RUN' stopped at my added station saying ' encroachment at this station blocks out the cross-section'. What is the issue on it, if anyone has any idea on it. Will appreciate.

 

[RWF7437]

There is not enough information in your post to answer your question.
Try plotting the cross sections or sections which are creating the error message and posting them here. That may give you the answer or provide enough information so that others may be able to help.

 

[froude]

did you add new cross-sections or did you replace existing cross-sections w/ survey data?

there's a possibility that the values in the encroachment table don't match the stationing of the cross-section. e.g. your encroachment may have been based on a section starting at station 1000 but now your cross section starts at station 0.

 

[sujanshakya]

Well i resolved that issue. but, Now I tried to run floodway encroachment on FEMA cross sections just addding the proposed bridge, no more surveyed x-sections. As, the case is widening i.e proposing 130ft long bridge in place of 50 ft existing bridge, There is a rise in WSE (encroachment). Since there is only one fema cross-section upstream of bridge (proposed bridge is almost at last station of FEMA detailed study), how can i lower this WSE (lowering the proposed encroachment value).
Thanks for helping me out..

 

[sknight701]

I would have expected the water surface to drop due to increasing the bridge opening. Did you analyze your ineffective flow stations and elevations properly to account for the change in the bridge? You might want to post your site plan with cross sections and maybe the RAS report too.

 

[RWF7437]

"Try plotting the cross sections or sections which are creating the error message and posting them here. That may give you the answer or provide enough information so that others may be able to help. "

"You might want to post your site plan with cross sections and maybe the RAS report too."

This is becoming less and less clear. Are you trying to do an encroachment analysis OR are you trying to analyze a bridge replacement ? The two are not identical problems.

 

[froude]

How far upstream of the proposed bridge is the existing FEMA section? As sknight said, your ineffective flow elevations could be a culprit. You may verify expansion/contraction coefficients. Depending on how far upstream the next section is, you might need to interpolate or insert more sections in between.

good luck!