CASE STUDY
The Damodar Valley Flood Control Scheme
(Ajit.K. Dasgupta and D.W. Pearce)The last chapter studied the application of cost-benefit analysis to the choice of site for a
particular project. The present chapter is concerned with evaluating a project is already
in operation.
- THE DAMODAR VALLEY SYSTEM
The Damodar river rises in the Palamau hills, Bihar (north-east India), at an elevation of
about 2000 feet. It flows eastwards for about 180 miles through Bihar and enters the
deltaic plains of West Bengal below the coal-mining centre of Raniganj (see Fig. 1). It
continues to flow east and as it reaches the boundary of Burdwan district it is joined by
the river Barakor. The enlarged river flows along the boundary of Bankura and Burdwan
districts and then into the Burdwan district, passing just south of Burdwan town. About
ten miles east of Burdwan town, the river abruptly changes its course and turns south. It
bifurcates into the rivers Mudeswari and Damodar about two miles before entering
Hooghly district. In the extreme southern part of Hooghly district, some thirty miles
below Calcutta, it joins the Hooghly river which reaches the sea shortly afterwards.
The catchments area of the river at its mouth is about 8500 square miles, of which nearly
7000 square miles is the catchments area of the upper Damodar. (The confluence with
Barakor River is regarded as separating the upper and the lower stretches of the
Damodar.)
The topography of the Domodar valley changes from hilly and forest regions in the upper
portion of the drainage area to the flat deltaic plains of the lower region. This is reflected
also in the slope of the river, which is 10 feet per mile in the first 150 miles of its course,
3 feet per mile in the next 100 miles and less than 1 foot per mile in the last 90 miles.
The Damodar is a flood-prone rive. Since at least as far back as 1730, it has been known
to overflow its banks during the rainy season, leading to devastating floods in the lower
valley.
The occurrence of floods along the Damodar River is due in the first instance to heavy
storm-rainfalls during the monsoon period, and more generally to certain characteristics
of the river regime. Thus, in the earlier part of its course the river flows very rapidly,
eroding land and collecting silt, a tendency which has been accelerated by deforestation
in the upper reaches. J In its lower reaches, the flat deltaic plains of West Bengal, it
becomes a sluggish stream and discharges its flood waters and silt along its banks.