Natural Reach Shapes
As in most river models, a natural channel branch can be taken as a series of gradually varying sections. Natural channels segments that describe a branch are defined using an upstream and downstream open channel section element. The following section shapes may be used to define natural channels:
For natural sections, the engine will automatically insert the required computational sections along the reach by interpolating a top width versus elevation table that is dynamically built according to the maximum number of input points that describes either end-section.
Note: The SWMM engine does not support the notion of a natural channel described between two open channels cross-sections. So, when solving using the SWMM engine, each open channel reach will be modeled using the upstream section shape. Using a conduit element with an irregular shape will provide computational consistency between the SWMM and implicit engines.