Flood Study for Gulshan, Banani, Baridhara

Location

Dhaka, Bangladesh

 

Type of Project

Flood Control

 

Period of Study

Sep 1998 to Dec 1998

 

Client

Dhaka Water Supply and Sewerage Authority (DWASA), Dhaka

Water level hydrograph at Begunbari Khal sluice under the actual gate & pump operation strategy during 1998 flood

Description

Bangladesh faced a catastrophic flood in 1998, duration of which was unusually high: from around mid-July to the end of September. During this period, a large portion of Dhaka City also suffered from the flood. Substantial part of Gulshan, Banani and Baridhara areas remained under water for a prolonged duration. This caused serious inconvenience to the dwellers of these areas where many of the foreign delegates also reside. SWMC carried out a study for the Dhaka Water Supply and Sewerage Authority (DWASA) to investigate the causes of and remedial measures to be taken up to overcome such flooding situation of City areas.

The major drainage channels lying within the study areas are: Gulshan Lake/Khal, Banani/Mohakhali Khal, Dhanmondi Lake, Paribagh Khal and Rampura/Begunbari Khal. The downstream end of Begunbari Khal falls into the Balu River. A hydrological and hydrodynamic model was set up comprising the drainage channels. MIKE 11 river modelling software of the Danish Hydraulic Institute (DHI) of Denmark was used to set up the model. The model was calibrated against observed water levels of the Begunbari Khal sluice (FS8).

The calibrated model was then used to test several options to find out the most probable cause of flooding of the areas concerned, and to test remedial measures to be taken up to avoid such a situation in future.

Reviewing all the options tested considering the prevailing hydrological situation of 1998 flood, it has been found that the design operation strategy of the DIFPP for the Begunbari Khal sluice (FS8), viz. closing of the gates at water level 4.5m PWD and pumping with 50 nos. 5 cusec pumps would be necessary to avoid the unwanted inundation within the Gulshan, Banani and Baridhara areas. The timing of closing of the gates in 1998 flood period was not timely, and the implemented pumping strategy was quite insufficient to get rid of the already flooded condition.