In modern cities worldwide, including those in Pakistan, one of the most pressing yet often overlooked challenges is the management of storm water. Each monsoon season, Pakistani cities like Karachi and Lahore face heavy rainfall that often leads to urban flooding. Millions of liters of runoff water from roads and rooftops are quickly directed into drains, ultimately flowing into rivers or seas. This deprives local environments of natural water replenishment, while compounding flood risks downstream.
Bioswales (shallow, vegetated channels designed to capture, filter and slow down storm water runoff) present a nature-based solution to this issue. As the water passes through soil and plants, pollutants and sediments are filtered out, improving water quality. By slowing down the flow, bioswales reduce flood risks, maintain groundwater levels and ease the burden on municipal drainage systems.
In Pakistan, where rapid urbanisation often outpaces infrastructure development, bioswales can be integrated into new housing projects and public spaces. This strategy is especially vital in flood-prone regions like Khyber-Pakhtunkhwa. By enhancing soil permeability, bioswales contribute to aquifer recharge and strengthen resilience against climate change-induced weather extremes.
Urban trees are another critical component of sustainable water management.
Their extensive root systems stabilise soil, reducing erosion and promoting water infiltration. In cities such as Islamabad, expanding tree cover helps mitigate the urban heat island effect, providing shade and cooling through evapotranspiration. Additionally, trees filter air pollutants, produce oxygen and support biodiversity.
Beyond ecological benefits, trees contribute to food security when fruit-bearing species are planted in public spaces or community gardens. This practice can be especially impactful in lower-income areas, offering nutritious produce and fostering social cohesion.
Other nature-based solutions, like permeable pavements and green roofs, complement bioswales and urban tree planting. By allowing rainwater to seep through surfaces, permeable pavements reduce runoff and replenish groundwater. Green roofs, meanwhile, absorb rainfall, lower building temperatures and create habitats for pollinators. These approaches collectively enhance climate resilience, improve air quality and elevate public health.
Dr Anila Kausar, Dr Intikhab U1fat
Karachi
