I am modelling a channel that splits into two part way down and am particularly interested in the inundation of the area between the two channels.
I have floodplain topography that is lower than the channel invert in some places and as a result I have some cross sections that have no flow in the channel (it is all in the overbank areas). To solve this problem I want to put levees on either side of both channels (downstream of the split) to ensure the channel fills up before flow is routed onto the floodplain.
However, I understand that the levee should be on the edge of a cross section and the area beyond this should be modelled as either a storage area or another reach. I want the flow to continue moving in the floodplain so a storage area is not appropriate.
So, my problem is how to set up the area between the two channels? If I set up a new reach either side of each original channel I will end up with 6 near-parallel reaches! Is it possible to model the area between the two channels with one new reach, even though this area has contribution of flow from both channels?
Any help would be really appreciated. Many thanks, Kate
You can put the levees bounding your main channel. They don't have to be on the cross section edges. Just be careful and understand that when the levee markers overtop, water will instataneously fill the interior side to the same level as the main channel. Otherwise, multiple parallel reaches is the way to go.