Leh Sel Riskine Karşı Uzmandan Yapısal ve Yeşil Önlem Çağrısı

Structural, green measures needed to curb Leh floods: expert

RAWALPINDI: Development of green areas while ending grey structures along Leh Nullah, construction of check dams, delay-action dams and percolation reservoirs along the Margalla Hills, and management of sewage discharged into the nullah, coupled with structural flood engineering, are the only solutions to avoid flood-like situations in the twin cities of Rawalpindi and Islamabad. Dr Amir Haider Malik, former adviser to the rector of Comsats University, told Dawn that the recurring annual flood crises in the Leh Basin were not unmanageable natural disasters but the direct consequence of intense urban expansion, uncoordinated inter-city planning and long-standing channel degradation. Relying on emergency response measures and annual pre-monsoon dredging was financially inefficient and unsustainable as a long-term solution, he said. Achieving a permanent solution required a paradigm shift: transitioning from treating Leh Nullah as an open sewer to managing it as a vital hydrological asset. “By pairing structural flood engineering in Rawalpindi with upstream runoff attenuation, Managed Aquifer Recharge, wastewater interception and innovative financing models, the twin cities can transform a seasonal flood hazard into a safe, ecologically sustainable and successful resilient urban model even for other countries,” he said. Dr Malik said the Leh Nullah project was “rather a gold mine of fund generation”, not only to fund the required anti-flood measures in the region but also to generate additional money for other related projects for the environmentally sustainable development of the region. He said the Leh Basin constituted a vital shared hydrological watershed covering approximately 235 square kilometres across the twin cities of Islamabad and Rawalpindi. Originating in the Margalla Hills, tributaries, including the Saidpur, Tenawali, Bedran and Bedar nullahs, funnel runoff through Islamabad’s urban grid before converging into the main Leh Nullah near the I-8 and I-10 sectors. From this confluence, he said, the primary channel traversed densely populated urban sectors of Rawalpindi for nearly 30 kilometres before discharging into the Soan River. Historically a natural, self-cleansing freshwater system, he said, rapid urbanisation over the past four decades had transformed the stream into an overloaded drainage corridor. Because the steep slopes of the upper catchment accelerate stormwater through Islamabad into a significantly flatter lower basin in Rawalpindi, fast-moving runoff frequently bottlenecks within the constricted downstream channels. Talking about the root causes of flooding, hazards and environmental impacts, he said extensive bank encroachment, undersized historic bridges and localised structural constrictions, particularly at the Katarian, Ganjmandi and Gawalmandi bridges, severely restricted hydraulic capacity. He said uncontrolled paving and deforestation in the upper catchment drastically reduced natural rainfall infiltration, generating swift and severe peak runoff. Systematic dumping of municipal wastewater, solid waste, construction debris and organic refuse also significantly degraded the channel’s hydraulic cross-sectional area, he added. He said there was a total lack of upstream stormwater retention or delay-action facilities upstream of Rawalpindi. “The Leh Basin receives roughly 50 per cent of its total volume from external basins (such as the Soan, Kurang and Haro basins via the Simly, Rawal and Khanpur dams), substantially increasing overall baseline water volume,” he said. “Monsoon flash floods in the basin exhibit short lag times, typically requiring only one to three hours between intense cloudbursts over the Margalla Hills and peak surge downstream in Rawalpindi. “Inundation generally lasts between six and 24 hours, and sometimes can take many days, though floodwaters linger significantly longer in low-lying residential sectors in Rawalpindi,” he said. “The July 2001 flood, which recorded over 620mm of rainfall in only 10 hours, underscored the severe vulnerability of areas like Arya Nagar, Nadeem Colony, Dhoke Ratta and Gawalmandi.” Over 400,000 residents live directly within high-risk flood zones, he said. Direct impacts included loss of life, structural collapse of informal settlements, severe commercial disruptions in major wholesale markets and widespread damage to municipal infrastructure. He said commercial cattle farms and illegal livestock operations along the banks discharged manure and organic slurry directly into the stream. The channel receives over 100 million gallons per day (MGD) of raw domestic and industrial sewage from both cities, he added. “A permanent resolution requires shifting from piecemeal channel dredging to a multi-tiered, basin-wide management framework that combines structural and hydrological engineering with Managed Aquifer Recharge (MAR) of the depleting and polluting Leh Basin aquifers,” he said. Dr Malik proposed slope and stream stabilisation measures, saying: “Construct gabion structures, check dams, delay-action dams and percolation reservoirs along the Margalla Hills to regulate flood speed and encourage groundwater recharge.” He also proposed establishing “dual-purpose flood detention ponds and micro-dams along major tributaries in the upper sectors E-8, F-10 and I-8”. He said dedicated sewage interceptor pipelines should be constructed, comprising parallel interceptor gravity-flow trunk sewers along both banks to isolate raw municipal sewage and route it to decentralised wastewater treatment plants (WWTPs), reserving the main channel bed exclusively for stormwater. “Enforce strict zoning regulations to clear direct floodways, relocating high-risk structures to establish continuous green buffers and public parks along the banks,” he said. He added that executing a permanent, basin-wide intervention required a blended financial framework combining international, national and innovative private-sector capital. He said public agencies could leverage international climate-resilience mechanisms — such as the Green Climate Fund (GCF), Asian Development Bank (ADB) and World Bank — targeting urban climate adaptation and disaster risk reduction (DRR). These funds would primarily back upstream retention infrastructure, advanced flood early-warning systems and ecological restoration along the hills. Published in Dawn, September 8th, 2026