Sep 04, 2007

Cape Town, South Africa, Cleaning Its Storm Water Pipes

Urbanization has promoted regional flooding

The city of Cape Town, South Africa, is working to clear debris and litter from more than 6,000 km of storm water pipes and drains. Officials hope the undertaking will reduce the risk of flooding.Blockages caused by rubbish dumped in canals, drains and rivers have strained the region's storm water system, despite the allocation of $76 million this year for its cleaning needs. Torrential July downpours and resulting floods have displaced at least 38,000 residents from their homes to informal settlements. The city has already invested millions of dollars in addressing damages.Barry Wood, city manager of catchment, storm water and river management, said the Blomvlei, Vygekraal and Liesbeeck were among several rivers that burst their banks due to blockages."Flooding cannot be prevented completely, as rainfall often exceeds the capacity of storm water systems," he said. "Moreover, rampant urbanization has increased the extent of hardened surfaces, resulting in more storm water runoff being diverted to storm water systems instead of being soaked into the ground."Cape Town's executive director of housing, Hans Smit, said consecutive cold fronts, the rising groundwater table and drain outlet blockages caused July's heavy flooding. Council workers have removed more than 2,400 cu meters of rubbish and storm water debris from the city's pipe network, 1,000 km of river, 140 km of open channels and canals and 680 detention ponds. The city has also supplied more than 1,700 cu meters of sand and 1,500 cu meterse of rubble to fill in low spots and raise floor levels in 70 of the hardest hit settlements.Informal settlements on the Cape Flats and areas near storm water ponds, rivers, canals, wetlands and mountain slopes that have been affected by fire are among those most affected by the flooding. Part of Cape Town's flood risk strategy is to upgrade the 226 settlements that have been established, 25 percent of which were affected by this year's floods, compared with 80 percent seven years ago, said Noahmaan Hendricks, city director of development services.Hendricks attributed the improvement to regular cleaning operations, improved drainage systems and community education programs. He noted, though, that many shack dwellers continue to build in flood-prone areas despite city warnings.The main aspects of Cape Town's informal settlement cleanup include channelling water away from houses, filling depressions in access tracks and removing skips placed near storm water intakes.