Module 6: Routing Concepts

Theodore G. Cleveland, Ph.D., P.E, M. ASCE, F. EWRI

21-23 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

Channels Reservoirs

Infiltration Loss

Snowpack

Rainfall, P(t)Snowfall

Snowmelt

Runoff 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

T

SOI

Upstream Hydrograph Downstream Hydrograph

Module 6 11

SOIT )(

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

Run

off

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

Run

off

These two must transit the “rose” sub-basin

Run

off

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