Managing swamped conurbations

Factually, urban flooding is the fallout of accumulated rainwater in built-up areas where it cannot be absorbed, leaving it to pool on roads and over built-up infrastructure. This runoff overwhelms the capacity of drainage systems, such as storm sewers.

Consequently, urban flooding can occur regardless of whether the affected communities are located within designated floodplains or near any body of water. Although the current government is working hard to devise policies to control urban flooding, rainwater harvesting has emerged as the most widely considered solution, and one that has already yielded results.

In rainwater harvesting system, the rainwater is collected and stored from surfaces like roofs using pipes. This water goes into tanks or recharge wells to save water and help underground water levels grow.

To ensure the system's success, the authorities need to focus on three main areas:1) Drainage channels must be managed separately through a collaboration between the irrigation department and the concerned municipality or development authority.

There must be a strict prohibition against using drains as disposal sites for solid waste, as waste accumulation and encroachments are the primary catalysts for drain overflows during heavy rains. Consequently, the embankments should be paved, well-lit and lined with green belts.

Furthermore, paving these channels will facilitate periodic cleaning and reduce risks for maintenance workers by minimizing their exposure to foul odors and hazardous waste.2) The maintenance of drainage system should be done in routine, not as emergency arrangement.

The entire channels from outfall to upstream should be cleared of silt, debris, vegetation and other waste.3) The pumping infrastructure designed decades ago should be reviewed and expanded for today's wastewater volumes, with reliable backup power. Wherever topography permits, gravity-based drainage should be preferred over pump dependent system.

It is imperative to adopt a sustainable drainage system, as it aligns modern drainage infrastructure with natural water processes and consequently becomes part of a larger green infrastructure strategy. This strategy proves more compatible with stormwater surges, flood overflows and soil percolation.

Ultimately, these efforts aim to mitigate the disruptive effects that human development has had, and may continue to have, on the natural water cycle - particularly regarding surface runoff. An alternative to grey infrastructure is green infrastructure, which refers to amalgamation of a set of strategies for absorbing and storing stormwater at or close to the location where it falls.

For instance, intermittent large open spaces, rainwater collection devices, swales and Miyawaki urban forests (a novel idea gaining momentum in Pakistan) serve as highly effective tools to mitigate urban flooding. This green infrastructure serves as an exceptionally effective and cost-efficient method to reduce the severity of urban flooding.

Caution must be exercised when adopting a rainwater harvesting system. Unpredictable rainfall patterns and high upfront installation costs pose significant challenges, as the setup requires advanced infrastructure like tanks, pumps, pipes and filters. Furthermore, routine maintenance - frequent cleaning of gutters, inlets and filters - is essential to prevent blockages, algae growth and contamination.

Finally, because storage tanks have limited capacity, they risk overflowing during torrential storms. Above all, lack of a comprehensive National Urban Policy has left debilitating effects upon urban infrastructure. It is time to adopt a logical course of action that implements comprehensive statutory, engineering, environmental and maintenance policies to safeguard our cities.