Non-Orthogonal Channel and Reservoir Routing in GSSHA
2008
Downer, Charles W. | Ogden, Fred L. | Neidzialek, Justin | Byrd, Aaron
The GSSHA model is a continuous, physics based, distributed hydrologic model intended for general hydrologic/hydraulic analysis. A previous limitation of the model has been the inability to simulate reservoirs and hydraulic structures that typically control the flow from reservoirs. Reservoirs are widespread in many watersheds such that the ability to simulate them is critical to basic hydrologic analysis. In many hydrologic studies, the focus is on the reservoirs. The GSSHA model has been modified to include reservoirs and many common hydraulic structures that control flow from reservoirs, as well as flow at road crossings, flow through embankments, and other flow altering features. Another previous limitation of the GSSHA model has been the need to represent the stream network in an orthogonal fashion. That is, stream cells had to be aligned with overland flow cells, in the x- and y-directions, and be the same size as the stream cells. This requirement limits the accuracy of the stream network to the accuracy of the overland grid. Requiring orthogonal channels also tends to make the stream segments longer in the model than they are on the ground, forcing the use of less physical parameters for channel flow. These limitations have been eliminated by allowing non-orthogonal stream networks to be included in the GSSHA model. That is, stream cells do not have to correspond to overland flow cells, and do not have to be aligned in the x- and y-planes. Along with the new freedom of channel alignment comes the ability to decouple the stream cells discretization from the overland flow plane discretization and to vary the channel discretization throughout the network.
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