Floodplain

[Karin&Bethi]

Dear Chris,

In our model the valley through which the river flows widens up at the most downstream section. So we used floodplains to define the channel geometry at this section. In the outputs we get higher flow depths in the cross sections with floodplains than in the cross sections upstream with no floodplains.

Why? We suppose, that the water downstream should dispread over the floodplain and as a consequence the flow depht should be not so high.

Yours sincerely
Karin & Bethi

[Chris Maeder]

Karin & Bethi:

Are you comparing "apples to apples"? Are the channel cross section areas the same for the model with overbank areas and without? Or, did you convert some the channel cross section area over to overbank area?

The key to answering this is to look at the conveyance computed at each cross section.

Sincerely,

Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com