A component of the drainage improvement undertaken by the Dhaka Water Administration and Sewerage Authority (DWASA) concentrated on two important drainage channels in Dhaka City-Dholai Khal and Segunbagicha Khal. The Dholai Khal carries storm runoff from densely populated old Dhaka, while the Segunbagicha Khal drains the central part of Dhaka City.

SWMC has done a mathematical model study to examine the impact of an additional storm water flow to the Dholai Khal pumping station and finally the water would be diverted from the Segunbagicha Khal to the Dholai Khal through a proposed link sewer. Two catchment models were set up incorporating all features of the drainage system, including closed conduit box culvert and open channels both natural and manmade, storage basin and pump station.

The model results indicated that a significant volume of water could be diverted through the link pipe without flooding around the open sections of the Dholai Khal system. However, the Dholai Khal pump will need to operate fora longer period to discharge the additional flow into the river.

Outputs from the model were also analysed by the Geographic Information System (GIS) with inputs from Digital Elevation Model to produce waterlogging maps for the affected area under different hydrological conditions. The maps reasonably reproduced the physical conditions of waterlogging that existed during September and October of 1996.