Abstract
Dhaka, the capital city of Bangladesh with rapid and unplanned urbanization, is subjected to annual average rainfall of 2,076 mm. The intensity of rainfall during 10 years recurrence interval and 1 h duration of the city is 98 mm/h. The stormwater drainage systems of the city are often unable to manage peak runoff volume and hence urban flooding is common after medium to heavy rainfall events. A proposal to introduce leaky-wells using water sensitive urban design (WSUD) principles was investigated for Dhaka’s drainage network to transfer the present unsatisfactory situation into one which is sustainable. The regime in balance strategy was considered to control the stormwater for 100 years recurrence interval. We applied scaling theory to 57 years (1953–2009) daily rainfall data for the estimation of sub-daily rainfall intensity values. It was found that two leaky-wells; each with depth H = 2.0 m and diameter D = 2.0 m, in 500 m2 allotment can improve the situation. The emptying (drain) time of the proposed device is around 1.25 days, which meets the standard criterion. Groundwater table, soil hydraulic conductivity and topographic slope of Dhaka also support for installations of leaky-wells.
Highlights
The existing drainage system in Dhaka, Bangladesh focuses on collecting the stormwater as completely and as quickly as possible and discharging it directly to local waterways
The study was conducted in Banani suburb of Dhaka City, which is located besides a lake and the existing drainage system discharges the collected stormwater into it
The estimated emptying time for 100 years return period of the proposed leaky-well is 1.25 days, which meets appropriate criterion listed in the Table 3
Summary
The existing drainage system in Dhaka, Bangladesh focuses on collecting the stormwater as completely and as quickly as possible and discharging it directly to local waterways. This system has proven unsatisfactory and it leads severe flooding in low-lying areas. Appl Water Sci (2013) 3:115–123 urbanization, fraction of pervious area is reduced resulting in low stormwater recharge into the aquifer. The annual average rainfall of the city is 2,076 mm (Ahammed and Hewa 2011). The mean frequency of daily rainfall intensity equal or greater than 100 mm/day in a year is 2 (SD = 1.5)
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