Expert names measures to reduce flood risk in Rawalpindi and Islamabad
In Rawalpindi and Islamabad, Pakistan, engineering structures, bank greening, runoff retention in the headwaters and wastewater diversion are needed to reduce the risk of flooding in the Leh Nullah catchment. This assessment was expressed in a comment to Dawn by Dr Amir Haider Malik, former adviser to the rector of COMSATS University.
According to him, annual flooding in the Leh catchment is not an uncontrolled natural phenomenon but is linked to intensive development, uncoordinated planning by the two cities and degradation of the channel. He believes that emergency response and annual channel clearing before the monsoon season are not a financially effective and sustainable solution.
Causes of flooding
The Leh catchment covers about 235 square kilometres in Rawalpindi and Islamabad. Tributaries, including Saidpur, Tenawali, Bedran and Bedar, direct runoff from the Margalla Hills through Islamabad’s urban development to the main channel near sectors I-8 and I-10. Leh Nullah then runs through densely populated areas of Rawalpindi for nearly 30 kilometres and flows into the Soan River.
Malik stated that the channel’s capacity is limited by development along its banks, undersized old bridges and local bottlenecks, including near the Katarian, Ganjmandi and Gawalmandi bridges. He named uncontrolled paving of land and deforestation in the upper catchment, as well as the discharge of household wastewater, garbage, construction waste and organic residues, as additional factors.
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According to the expert’s assessment, more than 400,000 people live in areas at high risk of flooding. During monsoon downpours, the flood peak can reach Rawalpindi one to three hours after heavy rainfall in the Margalla Hills. He also noted that during flooding in July 2001, more than 620 mm of precipitation fell in 10 hours, demonstrating the vulnerability of several city districts.
Proposed measures
The expert proposes building gabion structures, check dams, embankments to slow runoff and infiltration reservoirs in the Margalla Hills. Other measures include creating ponds for temporary retention of floodwaters and micro-dams on tributaries in sectors E-8, F-10 and I-8.
Malik also called for laying collectors along both banks to divert untreated urban wastewater to decentralized treatment facilities, leaving the channel only for stormwater. He proposed strengthening zoning, removing structures from flood-flow channels, and creating green buffer zones and parks. In his view, the comprehensive programme can be financed through national, private and international funds, including mechanisms of the Green Climate Fund, the Asian Development Bank and the World Bank.
