Extend the High Ground cross sections?

[Anonymous]

I’ve a cross section that is too short and does not extend all the way up to the maximum calculated water surface elevation. Hec Ras adds a so-called “vertical wall” at the end of the cross-section.
I plan on mapping the alluvial plain calculated in RAS Mapper.
Should I extend the cross section?
I’m an absolute begginer, so sorry for my question.
Thanks.

[Anonymous]

Yup.

Even though the water surface elevation may change once you extend the cross section. the current WSEL at the vertical wall is a good place to start. Extend you cross section to at least the elevation calculated

[ldguethle]

The advise to extend your cross-section will generally work if you have a floodplain with an increasing cross slope where eventually you have ground elevations greater than your water surface elevation.

However, if you keep extending your xsec and the ground is essentially flat, or you have a ridge and then the ground slopes down / away with the water surface above the ridge, then you may need to convert all or portions of your overbanks to 2D to best represent those areas. If you get into this situation as a beginner, it’s best you have someone review it and provide guidance. If you are not using unsteady and thus can’t use 2D, then it gets more challenging/less accurate but it can be accomplished in steady flow.

[Anonymous]

thanks to both

[Author]

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