TR(BR)-129 : Development of flood control regulation policy

Abstract

In India, reservoirs are frequently constituted to serve multiple purposes like conservation and flood control. The reservoirs that serve both these conflicting purposes have to be operated carefully taking into consideration all the issues involved. If more than one reservoir is to be operated in an integrated manner, the problem becomes still more complicated. Further, if the flood prone area is located far away downstream of the controlling structure, modelling of the uncontrolled catchment needs to be carried out in addition to judicious operation of the controlling structure.

In the present study, flood control regulation policy has been developed for Dharoi reservoir which is the major hydraulic structure in the Sabarmati basin in Gujarat state. In addition to serve the conservation demands, this reservoir is also operated to regulate the flow during floods such that the river flow at Ahmadabad (165 km downstream of the dam) does not exceed 14170 cumec at any time.

The methodology adopted in the report consists of modelling of the intermediate catchment (downstream of the dam) and development of regulation policy for the reservoir for downstream releases. The Catchment modelling has been carried out using synthetic unit hydrograph approach & the various parameters have been calibrated. Flood routing has been carried out for the river reach from the dam site up to Ahmadabad using the Muskingum Cunge technique. The routing analysis also considers lateral flow from the intermediate catchment.

A software has been developed to assist the operator at the dam site in deciding about the release at any time from the Dharoi dam. Data regarding hourly rainfall in previous periods in the intermediate catchment and past hourly releases are input to the program.