I am trying to model an off-channel water reservoir and am having a lot of trouble with instability. The reservoir is a raw water reservoir that receives water that is pumped from the neighboring river. I need to model a dam break to see what floods downstream. The reservoir is approximately 3,000LF off of a river so the terrain between the reservoir and river is not a straight slope downward, although all of it is below the dam and is low area. I thought about a storage area with lateral structure but it seemed that storage areas need to be below the neighboring river to receive water, the bottom of my reservoir is at elevation 136' and the river it will ultimately discharge to in a dam break is approximately 80'. Any thoughts or examples on how to model this reservoir is greatly appreciated.