1. Watershed Modeling using HEC-HMS and EPA-SWMM ©T. G. Cleveland, Ph.D., P.E. 25 July 2012 Lesson 14

2. Routing in SWMM Hydraulic routing by –Normal Flow –Kinematic Wave –Dynamic Routing Routing occurs in conduits

3. Open conduits –Normal and Kinematic, Manning’s only. –Dynamic, Unsteady GVF Equations (St. Venant) Closed conduits –Preissman slots except: Identified culverts (new feature, am not familiar) Identified force mains (after a pump) Conduits

4. Data –Length –Geometric shape –Resistance and added head losses –Inlet and outlet offsets –Maximum depth For closed geometry, sets fill depth For open geometry sets how deep water gets before program “wastes” water for numerical stability. Conduits

5. Data –Slope is NOT supplied, it is computed from node invert elevations. Conduits

6. Level pool routing in storage elements. Diversions and weirs are “special” conduits. –Flow over weirs is by weir equations and coefficients –Diversions is usually a fraction flow is diverted above some minimum value Pumps are “special” conduits. –Flow by pump curves Special Element Routing

7. In SWMM most useful routing is using the Full Dynamic method. –Normal flow does not handle backwater well. –Kinematic wave does not capture backwater well. Approximate “steady” conditions using long simulation times (and constant forcing functions), ignore early time. Guidelines

8. HMS routes, why bother? –HMS is not best tool when you have to estimate water surface elevations as part of the analysis. –SWMM can handle the water surface computations in a straightforward manner. HMS routes upstream to downstream; there is NO feedback – usually fine, except in low-relief regions where backwater (or reverse flows) matter. Uses