Storm Drain

The Storm Drain model in WMS allows you to use a pipe network coverage (and optionally a linked drainage coverage) to develop a storm drainage network and run the HYDRA analysis program that was previously a component within the FHWA's HYDRAIN suite of hydrologic and hydraulic computer tools.

Both a rational (design) and hydrographic analysis for storm drain systems (at this point sanitary networks are not supported) can be set up using the Storm Drain coverage in WMS. A network is created as a series of arcs connected by junctions. The pipe segments are assigned appropriate material and other properties for the simulation. A global set of properties may be defined, or individual properties for each segment. Junctions can be simple junctions, manholes, reservoir (storage), or the outfall. The simple network below illustrates how a storm drain coverages is used to develop a simulation.

Then entire storm drain model can be defined from a single coverage, however inlet nodes must be assigned appropriate surface drainage parameters. In a rational analysis this would be the contributing area, Tc, and runoff coefficient. For a hydrographic analysis this would be an actual hydrograph. In either case a drainage coverage can be used (developed from a DEM, TIN, or feature objects) in order to define/compute these parameters. In either case the storm drain inlet characteristics (size and type) must be defined. When using a drainage coverage these parameters are part of the node attributes of the drainage coverage. If the entire model is defined from the storm drain coverage then these parameters are defined as attributes of the storm drain nodes (the toggle in the Job Control to define the model from the storm drain coverage only must be turned on).

The picture below shows the same pipe network with a WMS drainage coverage overlayed that is used to define the surface drainage parameters.

In this example the underground pipe network essentially parallels the surface drainage, but this is not a requirement when developing a storm drain simulation.

Once the storm drain inlet, and network are defined WMS can write a standard HYDRA input file and launch the program. Results can be seen as plots using the plot wizard tools.