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DES 606 : Watershed Modeling with HEC-HMS. Module 6: Routing Concepts Theodore G. Cleveland, Ph.D., P.E, M. ASCE, F. EWRI 21-23 October 2013. Module 6. Outline for Module 6. Routing simulates movement of adis discharge signal (flood wave) through stream reaches.
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DES 606 : Watershed Modeling with HEC-HMS Module 6: Routing Concepts Theodore G. Cleveland, Ph.D., P.E, M. ASCE, F. EWRI 21-23 October 2013 Module 6
Outline for Module 6 • Routing simulates movement of adis discharge signal (flood wave) through stream reaches. • Accounts for storage within the reach and flow resistance. • Allows modeling of a basin comprised of interconnected sub-basins Module 6
Routing • Previous modules • Storage : similar ideas, recall HMS is NOT a hydraulic model. • Routing used to connect sub-basins together into an integrated hydrology model. Module 6
Rainfall-Runoff Process • Precipitation • Meterology, Climate • Runoff • Fraction of precipitation signal remaining after losses HMS – Basin Component • Watershed • Losses • Transformation • Storage • Routing Hydrologic and Simplified Hydraulics Module 6
HEC-HMS • Hydrologic Cycle Components in HEC-HMS (circa 2008) Snowfall Evapo- transpiration Rainfall, P(t) Snowpack Snowmelt Infiltration Loss Land Surface and Vegetation Runoff Runoff Channels Reservoirs Percolation Loss Module 6 Discharge, Q(t)
Routing Hydrographs • Routing is the process of predicting temporal and spatial variation of a flood wave as it travels through a river (or channel) reach or reservoir • Two types of routing can be performed: • Hydrologic routing • Hydraulic Routing • We will concern ourselves with hydrologic routing Module 6
Routing Hydrographs • Hydrologic routing techniques use the equation of continuity and some linear or curvilinear relation between storage and discharge within the river. • Lag Routing (no attenuation) • Modified Puls (level pool routing) • Muskingum Routing Module 6
Routing Hydrographs • Hydraulic routing techniques solve full versions of the St. Venant Equations for 1-dimensional free surface flow. • Generally these are handled in HEC-RAS, but a subset (simplified hydraulics) available in HMS • Kinematic wave • Muskingum-Cunge Module 6
Routing Hydrographs • Applications of routing techniques: • Flood predictions • Evaluation of flood control measures • Assessment of effects of urbanization • Flood warning • Spillway design for dams • Detention pond design • Vital for multiple sub-basin systems simulations Module 6
Routing Hydrographs • Problem: • you have a hydrograph at one location (I) • you have river characteristics (S = f(I,O)) • Need: • a hydrograph at different location (O) • This is a “routing” situation. • The “river” can be a reservoir or some similar feature Module 6
Upstream Hydrograph Downstream Hydrograph Routing Hydrographs Module 6
Routing Hydrographs • These “bar-heights” related by the routing table (like the storage-discharge table in prior module) Module 6
Routing • As a process diagram: Inflow (t) Stream geometric properties Wedge and Prism Storage Routing Model Stream resistance properties Outflow (t) Module 6
Routing Table Construction • Typically a hydraulic analysis (external to HMS) used to build a storage-discharge table Module 6
Routing and Watersheds • Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. Module 6
Routing and Watersheds • Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. These two must transit the “rose” sub-basin Runoff Module 6 Time
Routing and Watersheds • Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. Composite These two must transit the “rose” sub-basin “routed” to the outlet Runoff Runoff Module 6 Time Time
Routing Hydrographs • The routing relationships are usually developed external to HEC-HMS • Like rainfall and external hydrographs, use external tools to develop the storage-discharge relationships Module 6
HEC-HMS • Example 6 – Illustrate Routing Data Entry • Ash Creek Watershed • Subdivide into three sub-basins • Parameterize each sub-basin • Use Lag Routing (simplest model) • Examine results. Module 6
Summary • Routing is of two types: • Hydraulic • Hydrologic • Routing tables built outside HMS, then information imported. • May need hydraulic programs to develop routing tables Module 6