Types of Routing
Flood routing is technique of determining the flood hydrograph at a section of a river by utilising the data of flood at one or more upstream sections.
In various applications such as flood forecasting, flood protection, reservoir design and spillway design, two broad categories of routing can be classified as:
(a) Reservoir routing
The effect of a flood wave entering a reservoir is studied in reservoir routing. In reservoir routing, storage is a unique function of outflow discharge only i.e. S = f(Q). Reservoir routing is essential in
- Design of capacity of spillways and other reservoir outlet structures.
- In location and sizing of capacity of reservoirs to meet specific requirements. In this routing, to predict variations of reservoir elevation and outflow discharge, effect of flood wave is studied.
(b) Channel routing
In channel routing, change in shape of a hydrograph is studied as it travels down a channel. To predict outflow hydrograph at downstream locations, a channel reach and inflow hydrograph at upstream location is assumed to be known.
In flood forecasting operations and flood protection works, channel routing has most importance in acquiring information on flood peak attenuation and duration of high water levels. It is to be noted that unlike reservoir routing, in channel routing, storage is a function of inflow discharge and outflow discharge.