POST TIME: 18 June, 2019 11:27:07 AM
Heat waves and health
Urban design can create spaces of heat refuge at street level within cities
Mohammed Abul Kalam, PhD

Heat waves and health

Heat waves have direct impacts on mortality amongst the elderly and young but they also cause numerous indirect impacts such as stress on electricity networks, emergency services, hospitals and infrastructure stresses such as road damage and transport delays when railway lines buckled under the extreme conditions. The impacts of severe heat waves are likely to affect all sectors of the Bangladesh community, from the general public to government organizations and industries, health, utilities, commerce, agriculture, and infrastructure.
Dhaka and other city temperatures and city economics havea hidden relationship between sun and wind, and profits. Good urban design and walkability boost local economic activity by increasing public activity, but cities need to pay more attention to the effects of microclimates on streets and public spaces.
Urban design undoubtedly influences the urban economy. A simple thing like designing an area to make it more walkable can boost local business profits. This can also increase real estate value, create more and better jobs and generate stronger local economies.

Street temperatures also determine their walkability. With climate change bringing longer and more frequent heat waves; street temperatures will become even higher than at present. This will reduce walkability and, in turn, local business profitability.

Heat waves — Bangladesh’s biggest natural killers — are getting more frequent and hotter thanks to climate change. One day cities such as Dhaka may see unprecedented heat, perhaps 48C or higher. But research shows that smart urban design can create refuges in cities that could feel more than 10C cooler and without increasing energy use. And we can easily say that Bangladesh is not adequately prepared to deal with heat disasters and we can focus on the ability of our services to respond to and communicate about extreme heat events, it also raises an important question: how do we better prepare our cities for more frequent and hotter heat waves?

With increasing predicted temperatures and the impact of the urban heat effect (where urban space is much hotter than surrounding areas) to consider, there is increasing pressure on Bangladesh cities to support the health of their populations during extreme heat events.

Whilst it’s important to make sure our emergency services are able to cope in the best way possible, this is a reactive response that will help manage crisis situations. Reinforcing the electricity grid to make sure that outages are minimized is also valuable. However, proactively dealing with mitigation of extreme heat can take the pressure off services, minimize expense and most importantly, reduce heat stress.

How do we mitigate extreme heat?Urban forests have been found to be very effective methods for city heat mitigation. However, vegetation takes a long time to grow and may not be as appropriate in every part of a city, so we need a greater diversity of solutions.

It is important to design at the street level scale; particularly in those places used the most. The spaces between buildings are necessary for urban functionality and where people spend the most outdoor time.

Keeping cool on the streets:Research on urban microclimates from around the world has shown that we can control the thermal comfort of smaller spaces, without using more energy. This is not just about reducing the absolute temperature, it’s also about making people feel comfortable.

The experience of temperature is controlled by both personal and environmental factors. Combinations of air temperature, wind, humidity, and radiated heat will change the feeling, or apparent temperature, of the weather.

We can create spaces with optimum comfort levels through a combination of shading, reduced heat buildup in materials, humidity and wind management. Rather than trying to change the temperature of the whole city, we can provide heat refuges at street level to make the city more functional on hot days.

We know that a comprehensive toolkit is needed to understand how we can cool the city in different places. Trees and greening are important but aren’t practical everywhere, and certainly not when they are used in isolation.

Designs that also include redirecting wind, controlling humidity and water and that consider thermal qualities of materials are necessary. There are also further opportunities for enhanced cooling that use virtually no energy.

Researchshows that using on-site temperature and humidity sensors revealed temperature differences of up to 10C across a small urban block. In addition, whilst exposed sites were the hottest, they were also often the quickest to cool off. This gives us big clues into designing urban spaces for use across a whole day, where it’s important to minimize heat build-up but also to encourage rapid heat loss.

Global movement:This kind of work on the design with atmospheric conditions is beginning to be explored in cities around the world. Examples include climate engineers Transsolar, who was instrumental in demonstrating that Qatar’s 2022 World Cup bid was viable, showing how well designed stadia could mitigate the extreme temperatures of a Qatar summer.

In Taiwan construction is underway on the Jade Eco Park, a climatically controlled park that works to vary temperature, humidity and to provide clean air within microclimates to counter or enhance local climate conditions.

Bangladesh cities, with very particular weather conditions, need responsive design solutions that work with those kinds of factors. Urban design can create spaces of heat refuge at street level within cities. Bus stops, train stations and streets that need to be used even during the most extreme heat wave are places that can be cooled. If we can drop the temperature of these spaces by even a few degrees, we can save lives.

Considering this problem, we have to focus on tropical cities. We have to investigate the relationship between urban microclimate, labor productivity, sales revenue, and real estate values.

Is there, for instance, an optimum location for certain types of land use according to their suitability and need to use the footpath? If one side of the street is more exposed to the sun than the other, it may be more suitable for establishments that don’t make active use of the streetscape, such as stores and offices, rather than food shops and restaurants. Another question is does microclimate affect the productivity of businesses differently across urban and non-urban surroundings?

Part of the solution to rising urban temperatures could focus on street orientation and exposure to breezes. Priority could be given to siting food shops, for instance, in pleasant areas, with tables outside to help activate spaces. Instead of creating zoning that kills flexibility and dynamic spaces, planning guidelines for tropical street life should consider the types of businesses suited to specific street microclimates.

In a warming climate, designing for microclimate is more important than ever before to ensure urban life and economies can prosper. The writer is  former Head, Department of Medical Sociology, Institute of Epidemiology, Disease Control & Research (IEDCR) Dhaka, Bangladesh