Water Logging in Bangladesh

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  • Topic: Hydrology, Drainage, Surface runoff
  • Pages : 12 (3447 words )
  • Download(s) : 1394
  • Published : July 23, 2010
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STORM WATER DRAINAGE MODEL COUPLED WITH FLOOD DEPTH MAPPING: A NEW APPROACH TOWARDS SOLUTION OF URBAN DRAINAGE PROBLEMS Mir Mostafa Kamal* and M Fazle Rabbi** * River Hydraulics Division, Surface Water Modelling Centre, Dhaka-1206, Bangladesh ** Water Resources Division, Surface Water Modelling Centre, Dhaka-1206, Bangladesh ABSTRACT Storm water drainage and its management in many large cities in the world are becoming increasingly problematic. Unplanned or poorly planned urban development along with man made intervention in the natural drainage systems are compounding the fact. With the advent of very fast computing facilities, sophisticated mathematical modelling tools have come forward to solve urban drainage problems. A study was carried out for the Central part of Dhaka, the capital of Bangladesh, regarding the severe waterlogging problem recurring every time due to even a moderate rainstorm. An urban drainage modelling software, MOUSE of the Danish Hydraulic Institute (DHI) of Denmark was used in conjunction with Geographic Information System (GIS). Model based waterlogging maps (flooding depth and extent map) produced for September and October 1996 rain showed close matches to the real situation. Graphical two-dimensional animation of waterlogging and its improvement under several alleviation schemes were of practical help in visualising the real situation. The study results suggest that a meaningful solution for urban drainage problems can be obtained with better confidence of optimisation using the coupled use of an urban drainage model and flood depth mapping.

KEYWORDS Storm water; Dhaka City; Mathematical Model; Sustainable Management INTRODUCTION Background Storm water drainage and its management in many large cities in the world are becoming increasingly problematic. Unplanned or poorly planned urban development along with man made intervention in the natural drainage systems are compounding the fact. With the advent of very fast computing facilities through 4th generation computer, sophisticated mathematical modelling tools have come forward to solve the urban drainage problems. However, almost all relevant modelling software are designed for planning and designing of sewerage system for a design storm. It is hardly possible to foresee the impact of instant improved drainage facilities along with future urban development on the urban flooding and waterlogging problems. Dhaka is the capital of Bangladesh and nerve centre of its socioeconomic and political activities of the country. Its present population is about 9.6 million and has a population growth of nearly 4% per annum. Dhaka is going to be one of the ‘Mega Cities’ in the world by the year 2000. Therefore, urban development has been inevitable to cope up with the increasing thrust of the huge population. However, the urban development did not take place as systematically as it should be. Unplanned or poorly planned urbanisation comprising abolishment or constriction of natural stormwater carrying channels, filling up of low-lying areas and natural ditches - which were used to act as reservoirs, etc.- are the major causes for the stormwater drainage congestion in and around the Dhaka City. Moreover, stormwater drainage facilities did not improve significantly to accommodate the ‘too

rapid growth’ of the City. As a result, the City has been experiencing worsening waterlogging problem for the last decade. The problem of stormwater drainage was highlighted in the months of September and October 1996 when the City dwellers faced the worst ever waterlogging in Dhaka City. Human activities were almost suspended for few days due to the unusual waterlogging problem. The Central part of Dhaka City was the most suffered area. Case Study A study was carried out for the Central part of the Dhaka City regarding the severe waterlogging problem (SWMC, 1997). An urban drainage modelling software was used in conjunction with Geographic Information System (GIS) Model...
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