Can we tackle heavy rains in Karachi?

The residents of Defence Housing Authority (DHA) braved similar rains in 2020 and expected better results this time. However, little has changed as far as water accumulation is concerned.
Though the DHA and the Cantonment Board Clifton (CBC) have done some repairs and arranged a number of generator-driven pumps near low-lying areas, the magnitude of rainwater remains beyond their capacity to handle.
I have some observations and suggestions for the DHA and CBC. There are many areas where sewerage is diverted into storm water drains. The design velocity of sewerage and storm water is different.
Storm water drains have huge cross-sectional areas, while a higher cross-sectional area slows down the velocity of sewerage, which results in the solids settling down in storm water drains. The soil and the sand blown into the storm water drains also settle at the bottom.
All this, in turn, drastically reduces the depth and capacity of the drains. The designed gravity flow alone fails to drain rainwater, and, together with storm water overflows, it moves into houses.
To overcome these issues, the authorities concerned should remove RCC top covers and do thorough cleaning of the sludge that has settled in storm water drains. Sewerage should not be discharged into storm water drains. Huge capacity diesel engine-driven pumps should be installed permanently at the tail end of all storm water drains. These huge pumps will handle water flow during torrential rain and high tide. A monthly dredging out contract should be awarded to keep the drains dry and cleaned. Above all, netting should be installed to prevent plastic bags getting into the drains. The authorities concerned will do a lot of good by making use of these and other simple suggestions to manage the chaos.
S. Nayyar Iqbal Raza
Karachi