Sunday, August 11, 2019
BY MOEEN KHANWith the monsoon season now in full swing, residents of major urban centers in Pakistan will have to see sights they are all too familiar with – choked sewerage, overflowing gutters, blocked traffic and flooded streets. As inconvenient as these problems may be, there is much more at risk than what meets the eye.
With rising population, disordered urbanization, lack of environmentally sensitive policy-making, dwindling water resources, and climate change, major cities like Lahore are certain to find themselves in a precarious situation in the future if remedies are not introduced on an urgent basis.
Lahore’s single aquifer, for example, provides most of the water used for domestic purposes but the water table is declining by 2.5-3 feet per year due to over abstraction.
Much can be done to efficiently manage water resources in urban environments. Systematizing domestic water use, developing a well-planned water management system, introducing environmentally sensitive building technologies, and changing cultural norms dictating water use are important facets of such an approach. This is especially urgent if climate change resilient cities are to be developed in Pakistan.
Consider the manner in which major cities in the country are currently being developed. The two largest cities in the country – Lahore and Karachi, have lost greenery to urban sprawl. Both cities have also become concrete hardscapes that have brought about a new set of problems including, but not limited to, urban runoff and soaring temperatures during summers due to changing microclimate.
Take Lahore and consider how asphalt and concrete infrastructure is being built with little to no attention paid to the environmental impact. During the monsoon (or even the occasional showers) sewerage systems are overwhelmed and valuable rainwater is simply discharged into sewers. This, despite the fact that virtually nothing of the water seeps down into the aquifer because there is very little open soil to absorb the moisture. Bear in mind that groundwater is also the primary source of water for a city of 12 million people, a resource that is being depleted at an alarming rate.
There are a number of solutions that have successfully been adopted by cities around the world. Roads, pavements, parking lots and other similar structures are now being built with pervious concrete and porous concrete.
Instead of causing flooding or being discharged into the sewers, such construction materials allow valuable rainwater to seep through to the aquifer.
In other words, a simple change in material use and design prevents urban flooding and stores water for future use, all with virtually the same structural integrity. While the initial costs are higher as compared to conventional concrete/ asphalt, the porous variety is significantly more affordable in the long run.
With a life expectancy of around 20 years, it has lower installation and life-cycle costs and does not necessarily require investment in stormwater management infrastructure such as stormwater gutters. There are other advantages associated with such a design approach as well. Reduced water on roads during rainfall decreases the likelihood of traffic accidents.
Here is an example of how efficient porous asphalt roads are at preventing runoff.
Video courtesy: City of Burnsville, USA.
Concrete or asphalt infrastructure also absorb more heat during the daytime and emits it during the night. According to studies, hardscapes are among the primary reasons why microclimate in a city is 3-4 degrees higher than surrounding areas, a phenomenon known as the Urban Heat Island (UHI) effect.
However, simple design changes, such as painting the surface in a brighter colour helps to reflect most of the heat absorbed from sunlight, thereby fighting off the heat island effect. The advantages, such an approach offers, are not just limited to water use either. Lower temperatures translate to reduced energy consumption and reduced risk of heat-related illnesses/mortality for the elderly, young and poor.
The design thinking extends to residential infrastructure too. Pavements and parking areas in residential areas are also built using conventional concrete. However, environment-friendly designs for such structures are now widely being adopted as well.
Not only designs, like a grow-through pavement, are aesthetically pleasing, but they also help absorb rainwater (or even domestic water) and keep temperatures cooler.
With average temperatures rising owing to climate change, urban areas will become dangerously hot, leading to a sharp spike in water and energy consumption. It is of urgent importance to introduce wide-scale strategies to circumvent the impending threat if cities are to cope with such stress.
One effective way to do this is to alter the manner in which the roofs are designed. Simply painting the roofs in white colour can reduce air temperatures above the building by a margin of several degrees.
Similarly, green roofs – covering the roof with vegetation, are not only pleasing for the senses and reduce stress, but can help to decrease the temperature inside the building, combat urban heat island effect, help in noise reduction, cut back on carbon emissions, improve biodiversity and air quality. Most of the rainwater is retained by the soil instead of being discharged into the sewers or streets, thereby providing an excellent rainwater management strategy. Excess rainwater can also be stored in a water tank for later use. Even vegetated mats and plugs have been designed for rapid deployment of green roofs at a massive scale. There are also financial advantages associated with the design philosophy. Green roofs are estimated to increase the life of a roof by 200% and have the added effect of reducing energy consumption due to lower demand for air conditioning.
In cities across the world, community-driven projects have been initiated to allow residents to grow food on roofs as well. Such a technique has the added advantage of providing valuable household income for the poor.
Given the threat of climate change, civic bodies around the globe have progressively introduced policies, technological solutions and changes to the manner in which urban centers are developed and organised.
Pakistan, a country that is among states most threatened by climate change, has given scant attention to the matter. Of course, the solutions mentioned here are by no means exhaustive nor comprehensive, doing so is beyond the scope of this writing.
The aforementioned designs and systems have as much to do with preventing urban flooding as with ensuring that valuable water resources are preserved, that urban temperatures remain under control in a rapidly warming planet, and that a conscious approach regarding urban design is integrated into a cohesive urban development policy as part of Pakistan’s climate change risk management strategy.