connecting streams with different depths?

[PM_2009]

Hi,

I'm using GSSHA in WMS 8.2.

I was wondering what happens if I connect, for example, a trapezoidal channel with depth = 1.5 m to another trapezoidal channel with depth = 1m, and then use the "smooth stream arcs" so the channels are not running uphill at any point. Does the "smooth stream arcs" actually smooth the elevations of the banks of the channels, and does this mean that if a deeper channel connects to a shallow channel, the bottom of the channel goes half a meter up in the connecting point even when "the smooth stream arcs" show that the channels are smoothed?

Another question i have is that if the channel runs, for example, a meter below the grid (because, as in the reality, the channel goes through "hills" where the elevation of the ground is something like two meters above the general ground elevation), does the model add a meter to the defined channel depth or what? What is the relationship between the grid and the channel in this kind of situation? What if the water in the channel rises above the defined channel bank but not higher than the grid surface?

Thanks again for any answers!

-Pirkko-

[Clark Barlow]

Pirkko-

The smooth streams command smooths the elevation of the stream thalweg. This means if you smooth streams between two channels of different depths (1.5 m to 1.0 m, for example), you would not have an abrupt 0.5 m elevation jump.

As for the overland cell/channel interaction, it depends on what type of interaction you've specified in the project file. The GSSHA users manual discusses this: http://gsshawiki.com/gssha/Surface_Water_Routing:Overland/Channel_Interaction Hopefully this answers your questions.

-Clark

Edited September 16, 2009 by Clark Barlow