An estimated 2,600 houses and other structures fall within 30 feet of the Orangi Nullah’s way on both sides, an NED University survey has indicated to the Sindh government.
The university team undertook a hydrologic and hydraulic analysis of the nullah as part of a greater study on all of Karachi’s stormwater drains. This NED report is not necessarily final.
This work was commissioned by the chief minister after the disastrous August monsoon which paralysed Karachi last year. The Supreme Court has also ordered nullahs to be cleaned.
Orangi Nullah is one of Karachi’s big three. It is 11.25km long and sits in a densely populated neighbourhood.
The NED team performed a Global Navigation Satellite System survey to study the width and depth of the drain. Drones were used for an aerial survey to map its route. The nullah’s catchment area or collection area is 30.8 square kms. It can generate rainwater runoff as much as 45,439 cubic feet per second. If the August rain data of 270mm falling in 12 hours is used to project flooding outcomes, then the NED team estimated that 12,700 cfs would be produced.
If the government wants to clear 30 feet on either side of the Orangi Nullah then 2,656 structures would come in its way. Of these, only 1,703 would have to be over 50% removed. The others would suffer less damage.
The NED team has already surveyed the Mehmoodabad-Manzoor Colony Nullah where 238 houses and shops are going to be demolished to varying degrees. Work has already begun in that neighbourhood. Orangi and Gujjar Nullahs are next.
The government came under pressure to find a solution after the city was paralysed last year when a 90-year record was broken, according to the Met Office. The understanding is that the city's main 44 drains are choked with garbage and need desilting. The focus has been, however, on removing encroachments as well. The NDMA and FWO are working with the Sindh government.
In one meeting this week, it was discussed that the alignment of Gujjar and Orangi nullahs provided an "opportunity to develop a network of expressways in the city along with the existing Lyari Expressway".