RN-12 Hydraulic routing techniques

Abstract

Routing of flood in open channel is one of the unsteady flow problem of importance to engineers. Flood routing is a computational procedure aiming at tracing of a flood wave incident and known at the upstream location. The objective of flood routing is to find the maximum elevation reached and corresponding time, the maximum volume rate of flow, for use in the design of spillways, bridges, culverts, channel sections, etc., and total volume of flow for design and operation of storage facilities for flood control, irrigation and water supply. Engineers are mainly interested in finding the two field quantities which are stage and discharge( or velocity). In the case of hydraulic routing continuity equation and momentum equation are used. These are frequently referred to as St.Venant equations. These are as follows:

Continuity:

DA t Momentum:

ata

3 Q + = 0 a x

Q aQ A ax

2

+ Ag (Sf - So + ax ) = 0

where, A is area of the flow(m ), Q is discharge (m3/sec), g is

acceleration due to gravity(m/sec2) S

slope and Y is depth of flow.

f

is energy slope, So is bed

The above partial differential equations along with initial conditions and appropriate boundary conditions are solved using numerical methods. The finite difference models and the finite element models are commonly used. The review includes a discussion on the above in addition to the method of characteristics. The review also includes uncertainties, in natural flood flow, like flood plain and channel interaction, alluvial bed deformation etc.