Urban flood, its effects and management options : a case study of Dhaka city

Flood is a global phenomenon. It is considered to be both a blessing and cursedepending upon its nature. Flood is differentiated into many types' namely urban flood,coastal flood, river flood, flash flood etc. Urban flooding occurs in the urban areas dueto excessive rainfall, insufficient drainage capacity, encroachment of drainage area,storm surges, climate changes etc. Floods can develop slowly and be predictable or canoccur suddenly, such as is the case with flash floods. The unprecedented number ofrecent urban flooding events in some of the major countries like UK, Eastern Europe,China with the climate change predictions necessitates the study of flood in a moreholistic approach.The effects of urban flooding are enormous and manifold such as physical damage,effect on health and hygiene, water quality and the environment. Flooding in urbanareas creates huge economic loss as most of the structural developments and activitiesare placed here. Sewage water, wastes from different sources gets mixed with floodwater and contaminates the receiving water bodies and also the water supply systems.The study titled 'Urban Flood, its effects and Management Options: A Case Study ofDhaka' aimed to identify these risks, damages and impact on the interrelated physical,social and environmental factors associated with urban flooding and then outlined somedisaster management and planning options. Dhaka was selected as the case study areasince the city is one of the fastest growing mega cities of the world and has a longhistory of flooding problems which continues to threat the city resident's life andlivelihood activities.State-of-the-art models like MOUSE, MIKE21 and GIS software like ARCGIS,waterRIDE were used as tools to understand the underlying processes of urban drainagesystem that cause flood and also analyze the effects on the environment. Water qualitymodelling was conducted to assess how pollutants are transported and propagated withflooding. Climate change scenarios were considered because its linkage with flooding inthe current circumstances is unavoidable. Tangible and intangible both type of damagesincluding direct and indirect ones were assessed using different approaches. Tangibledamage assessment was done by using the depth damage curves and integrating theflood depth obtained from model results and identifying the affected property in a GISenvironment. Assessment of intangible damages mainly on health was explored in thisstudy which is often excluded from the mainstream flood disaster management studies.Disability Adjusted Life Years (DALY) estimates is given as indicators of the extent ofdiseases caused by flood. The Anxiety-Productivity-Income relationship wasestablished to show how flood brings in anxiety in a persons life and thereby decreasesthe level of productivity and income.Flood mitigation for Dhaka should integrate stormwater drainage and pollution control.A synergy between the structural and non structural measures is required to find asustainable solution to the flood problem. Flood disaster management in Dhaka city hasto be an integrated approach with the coordinated efforts of Government organizations,NGO's, CBOS and including public participation in planning and implementation of thepolicy and guidelines