Hec-ras Modeling 1

[Hydrostru]

How can I model a river which is "in the sky" with Hec_ras? The bank elevations are higher than adjacent aeras so once it is overtopped, the water will run away perpendically to the reach.

I was setting ineffective areas but it seems not working as the cals are showing the WS is a few feet above the bank elevations which in reality can not happen.

Thanks!

 

[gbam]

You can use lateral weirs and not return the breakout flow to the channel. We do this all the time for sections of rivers with levees.

 

[cvg]

reduce your flow until it doesn't overtop?

 

[Hydrostru]

Only 2-year can be contained and the 100 year is 5 feet above the bank elevations. I am trying to remodel based on gbam's suggestion.

 

[SMIAH]

Are you sure that this water will "run away"?
Then it would really be ineffective areas.

 

[Hydrostru]

Yes the water will be running away. It is weird that I compared "ineffective area method" and "Lateral weirs method" and the difference in WS is minimal and I still have a few feet overtopping.

 

[gbam]

Ineffective boundaries are typically ussed when water will "stack up" outside of the conveyance zone. Their use will not reduce the discharge as the lateral weir option will; which, from my understanding is what is happening here.