Rapid Urbanization

 Rapid Urbanisation: Heat Island Formation

As Kochi transforms into a concrete jungle with increasing urbanization, it also has its own " Urban Heat Island ", a term used to denote the unusual heating up of urban areas owing to excessive built-up area and infrastructure. Urban Heat Island (UHI), a measure of the near-surface air temperature contrast between urbanized and adjoining rural areas, is the most pronounced effect of urbanization. The heat island is an example of unintentional climate modification when urbanization changes the characteristics of the Earth’s surface.

 In a recent study where scientists of the Indian Institute of Technology Kharagpur used satellite images to examine land-use change in Kochi and 9 other metropolitan cities in the country, it was found that the urban area of Kochi had shown a "Substantial increase and spread" between 2001 and 2013. The scientists also noted that Kochi was one of the 3 cities where Dry Land had been continuously decreasing due to the rise in the number of construction projects. It triggers the formation of the Urban Heat Islands. Surface air temperatures in such places are far higher than in nearby rural areas. 

 HEAT ISLANDS: IMPACTS

 

Elevated temperatures from heat islands can affect a community’s environment and quality of life in multiple ways:

1.    Increases Energy Consumption

Heat islands increase the demand for air conditioning to cool buildings. In an assessment of case studies spanning locations in several countries, electricity demand for air conditioning increased approximately 1–9% for each 2°F increase in temperature. Countries where most buildings have air conditioning, such as the United States, had the highest increase in electricity demand. This increased demand contributes to higher electricity expenses.

Heat islands increase both overall electricity demand, as well as peak energy demand. Peak demand generally occurs on hot summer weekday afternoons, when offices and homes are running air-conditioning systems, lights, and appliances. During extreme heat events, which are exacerbated by heat islands, the increased demand for air conditioning can overload systems and require a utility to institute controlled, rolling brownouts or blackouts to avoid power outages.

2.   Elevated Emissions of Air Pollutants and Greenhouse Gases

Heat islands raise the demand for electricity in summer. Companies that supply electricity typically rely on Fossil Fuel Power Plants to meet much of this demand, which in turn leads to an increase in air pollutants and Greenhouse Gas emissions.

These pollutants are harmful to human health and also contribute to complex air quality problems such as the formation of Ground-Level-Ozone (smog), Fine Particulate Matter, and Acid Rain. Increased use of fossil fuel-powered plants also increases emissions of greenhouse gases, such as carbon dioxide, which contribute to Global Climate Change.

In addition to their impact on energy-related emissions, elevated temperatures can directly increase the rate of ground-level ozone formation. Ground-level ozone is formed when nitrogen oxides and volatile organic compounds react in the presence of sunlight and hot weather. If all other variables are equal, such as the level of precursor emissions in the air and wind speed and direction, more ground-level ozone will form as the environment becomes sunnier and hotter.

3.    Compromised Human Health and Comfort

Heat islands contribute to higher daytime temperatures, reduced nighttime cooling, and higher air pollution levels. These, in turn, contribute to heat-related deaths and heat-related illnesses such as general discomfort, respiratory difficulties, heat cramps, heat exhaustion, and non-fatal heat stroke.

Heat islands can also exacerbate the impact of naturally occurring heat waves, which are periods of abnormally hot, and often humid, weather. Sensitive populations are particularly at risk during these events.

• Older adults are among the most vulnerable to extreme heat events. Many physiological, psychological, and socioeconomic factors contribute to this danger. Older adults are more likely to be in poor health, to be less mobile and more isolated, to be more sensitive to high heat, and to live on reduced incomes.
• Young children tend to be more susceptible to extreme heat due to their small size and other characteristics. Children’s more rapid breathing rates relative to body size, time spent outdoors, and their developing respiratory systems raise their chances of aggravated asthma and other lung diseases caused by ozone air pollution and smog, which usually increases during heat waves.
• Populations with low income are at greater risk of heat-related illnesses due to poor housing conditions, including lack of air conditioning and small living spaces, and inadequate resources to find alternative shelter during a heatwave.
• People who spend their working hours outdoors are more prone to conditions such as heat exhaustion and heatstroke. They have higher exposures to ozone air pollution and heat stress, especially if work tasks involve heavy exertion.
• People in poor health, including people with chronic conditions, disabilities, mobility constraints, and those taking certain medications, are vulnerable to extreme temperatures. People with diabetes, physical impairments, and cognitive deficits are especially at-risk during heat waves.

 

Excessive heat events, or abrupt and dramatic temperature increases, are particularly dangerous and can result in above-average rates of mortality. From 2004 to 2018 the Centers for Disease Control and Prevention recorded 10,527 heat-related deaths in the United States, an average of 702 per year. These numbers include deaths where heat was the underlying cause and deaths where heat was a contributing cause.

4.    Impaired Water Quality 

High temperatures of pavement and rooftop surfaces can heat up stormwater runoff, which drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes. Water temperature affects all aspects of aquatic life, especially the metabolism and reproduction of many aquatic species. Rapid temperature changes in aquatic ecosystems resulting from warm stormwater runoff can be particularly stressful, and even fatal, to aquatic life.

One study found that urban streams are hotter on average than streams in forested areas and that temperatures in urban streams rose over 7°F during small storms due to heated runoff from urban materials.

Green infrastructure is one option to cool stormwater runoff and improve water quality. It can include the use of downspout disconnections, rain gardens, planter boxes, bioswales, permeable pavements, green streets and alleys, green parking, and green roofs; as well as land conservation efforts.

Heat Islands: Reducing the Risks

To safeguard against the acute effects of extreme heat on people’s health in the short term, local officials can establish Early Warning Systems and urban cooling centers, and raise awareness about risk factors, symptoms of heat-related illness, and when and how to seek treatment. In addition, they can protect or modify roads, train tracks, and other infrastructure by using more resilient materials, as well as implement energy efficiency measures to reduce disruptions of city services and stress on electricity systems during heat waves.

 To reduce the heat island effect and its associated risks over the longer term, communities can use four main strategies:

• Increasing tree and vegetative cover - Increasing tree and vegetation cover lowers surface and air temperatures by providing shade and cooling through evapotranspiration. Trees and vegetation can also reduce stormwater runoff and protect against erosion.                                                         
• Creating Green Roofs - Growing a vegetative layer (plants, shrubs, grasses, and/or trees) on a rooftop reduces temperatures of the roof surface and the surrounding air and improves stormwater management. Also called “rooftop gardens” or “eco-roofs,” green roofs achieve these benefits by providing shade and removing heat from the air through evapotranspiration.
• Installing Cool (especially reflective) Roofs - One made of materials or coatings that significantly reflect sunlight and heat away from a building – reduces roof temperatures, increases the comfort of occupants, and lowers energy demand.
• Using Cool Pavements - Using paving materials on sidewalks, parking lots, and streets that remain cooler than conventional pavements (by reflecting more solar energy and enhancing water evaporation) not only cools the pavement surface and surrounding air but can also reduce stormwater runoff and improve night-time visibility.

Typically heat island mitigation is part of a community's energy, air quality, water, or sustainability effort. Some Smart Growth activities also contribute to heat island mitigation or vice versa.

Activities to reduce heat islands range from voluntary initiatives, such as cool pavement demonstration projects, to policy actions, such as requiring cool roofs via building codes. Most mitigation activities have multiple benefits, including cleaner air, improved human health and comfort, reduced energy costs, and lower greenhouse gas emissions. Heat island mitigation can also help cities reduce the impacts of climate change.

WHAT WE CAN DO? 

• Increase shade around your home - Planting trees and other vegetation lowers surface and air temperatures by providing shade and cooling through evaporation and transpiration

• Use energy-efficient appliances and equipment - Using efficient appliances and equipment in your home can help to lighten the load on the electric grid during heat waves, thus ensuring a more reliable supply of electricity to your community

• Install Green roofs and Cool Roofs