SUSTAINABLE MANAGEMENT OF TIDAL RIVERS USING ROTATIONAL TIDAL BASIN CONCEPT: A CASE STUDY IN KJDR PROJECT

Abstract

In this paper, chronic drainage congestion problems created in the tidal river systems located in Southwest coastal areas of Bangladesh, due to embankment constructed to protect intrusion of saline water and tidal flood, an innovative approach for sustainable management of tidal rivers and drainage congestion by using redefined rotational tidal basin concept and its impact through field measurement and mathematical model study in connection with the KJDR Project are presented. A couple of years after construction of embankment, its impacts on river regime were found prominent. Rivers are dying due to siltation, resulting conveyance loss and obstruction to passing out of surface runoff from watershed consequently loss of agricultural productivity and severe environmental hazards. Maintenance of the tidal river is of utmost importance. The use of rotational tidal basin concept found quite effective for sustainable management of rivers and mitigation of longstanding drainage congestion. This approach is innovative and still experimental in nature. Redefinition of rotational TB concept is presented here considering real field situations. Hydraulic modeling was carried out for the different option scenarios of operation of tidal basin and to assess its hydraulic impacts on increasing tidal volume and thus reducing sedimentation rate. Modeling study predicted that the suitable basins can be utilized rotationally for effective management of tidal rivers and drainage congestions. Closing of operation of tidal basin (TRM) even for shorter period would cause significant conveyance loss and thus reduction of tidal volume. Lifetime of one tidal basin with no maintenance dredging can be 5 years but with periodic maintenance it can be 9-13 years. Field monitoring results demonstrated that if there is no TRM, about 1.0 m sedimentation could be taken place on the river bed even in 12 days.