FLOOD ROUTING IN A TYPICAL REACH OF NARMADA RIVER

Abstract

Flood Routing is a technique by which a flood hydrograph at any section in a channel is determined from. a known hydrograph at some upstream section in the same channel. It is important in flood forecasting, design of hydraulic structures estimation of sediment /pollution transport. In this work, reaches in Narmada River are attempted to perform the flood routing studies. For the purpose, a computer program for channel routing is used. The equations governing the flow are One-dimensional Saint Venant equations and this solved numerically by four point preissmann's scheme. However, the main limitation in the model is that the channel bed is assumed rigid. Required data for river cross-sections and observed hydrographs at different locations are collected from various sources. In the present study, first, the model parameters are calibrated using an indirect method for conservation of water flow. Flood routing in Narmada from Mortakka to Mandleswar is performed for five different flood events. The contributions to the flow from intermediate regions are considered by assuming four tributaries at equal intervals between the measurement sites. Flood routing computations show that the computed and observed hydrographs at Mandleswar match satisfactorily. In addition, generalized equations are derived for the peak discharge and time to peak discharge. These equations can predict well, the flood peaks and time to attain the peak at any place between Mortakka and Mandleawar, using the peak and time to peak values of hydrograph at Mortakka. In the study for the reach from Jamtara to Bermanghat, a methodology is developed to estimate the discharge hydrograph in two tributaries, Hiran and Sher using the observed hydrographs at Jamtara and Bermanghat. Taking the tributary discharges into account flood routing computations show the computed hydrograph and observed hydrograph at Bermanghat match satisfactorily.