Module 6: Routing Concepts Theodore G. Cleveland, Ph.D., P.E, M. ASCE, F. EWRI October 2013 Module 6 1

 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 2

 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 3

Watershed –Losses –Transformation –Storage –Routing Precipitation –Meterology, Climate  Runoff  Fraction of precipitation signal remaining after losses Hydrologic and Simplified Hydraulics HMS – Basin Component Module 6 4

 Hydrologic Cycle Components in HEC- HMS (circa 2008) Land Surface and Vegetation ChannelsReservoirs Infiltration Loss Snowpack Rainfall, P(t) Snowfall Snowmelt Runoff Percolation Loss Evapo- transpiration Discharge, Q(t) Module 6 5

 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 6

 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 7

 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 8

 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 9

 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 10

Upstream Hydrograph Downstream Hydrograph Module 6 11

 These “bar-heights” related by the routing table (like the storage-discharge table in prior module) Module 6 12

 As a process diagram: Routing Model Inflow (t) Outflow (t) Stream resistance properties Stream geometric properties Wedge and Prism Storage Module 6 13

 Typically a hydraulic analysis (external to HMS) used to build a storage-discharge table Module 6 14

 Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. Module 6 15

 Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. Time Runoff These two must transit the “rose” sub- basin Module 6 16

 Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet. Time Runoff These two must transit the “rose” sub- basin Runoff Time Composite “routed” to the outlet Module 6 17

 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 18

 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 19

 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 20