1. DES 606 : Watershed Modeling with HEC-HMS
Module 5
Theodore G. Cleveland, Ph.D., P.E
29 July 2011

2. Module 5: Routing
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

3. Module 5: 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.

4. Rainfall-Runoff Process
Precipitation
Meterology, Climate
HMS – Basin Component
Watershed
Losses
Transformation
Storage
Routing
Hydrologic and Simplified Hydraulics
Runoff
Fraction of precipitation signal remaining after losses

5. Land Surface and Vegetation
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
Percolation Loss
Channels
Reservoirs
Discharge, Q(t)

6. 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

7. 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

8. 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-Kunge

9. 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

10. Routing Hydrographs Problem: Need: This is a “routing” situation.
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

11. Routing Hydrographs
Upstream Hydrograph
Downstream Hydrograph

12. Routing Hydrographs
These “bar-heights” related by the routing table (like the storage-discharge table in prior module)

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

14. Routing Table Construction
Typically a hydraulic analysis (external to HMS) used to build a storage-discharge table

15. Routing and Watersheds
Typically – multiple sub-basins. Routing to move outlet from a sub-basin to main outlet.

16. 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
Time

17. 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
Time
Time

18. 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

19. HEC-HMS Example 5 – Illustrate Routing Data Entry Ash Creek Watershed
Subdivide into three sub-basins
Parameterize each sub-basin
Use Lag Routing (simplest model)
Examine results.

20. Summary Routing is of two types:
Hydraulic
Hydrologic
Routing tables built outside HMS, then information imported.
May need hydraulic programs to develop routing tables