What does it mean to plan for the future? In cities, this is the most important question for engineers, scientists and politicians. In this activity, we will talk about some of the trends in cities that force us to change and adapt - trends related to expansion. We will be talking about harmful effects such as flooding, contamination and the urban heat effect and how we can work to reduce these problems in the present and future. This is an activity that can be done at home or in-classroom, an adult is needed for maximum learning potential.
You may have noticed but cities are growing. Everyday more houses are being built and more offices are being created for them to work, this also means more roads, streets and avenues for them to drive on. Sometimes this means new parks and trees too, but not always. After watching the short video on urban expansion, please write down some of your observations.
Have students use their own trackers to write creative stories about the places water might visit in its movements.
As an extension, once there is a rain garden onsite, modify part two to observation of plants and insects that they see.
Explore the Map overlay tool from this aerial survey in 1949, then go into google earth and compare. What do you notice?
When cities expand, they build more roads to bring more people from their homes to schools, offices and recreation areas like malls. But what does this do to the environment. In many cases, this can mean increased flooding, increased heat and more water contamination. This happens because there is less space for plants when we use asphalt and other impermeable surfaces to build.
When there are more permeable surfaces, this helps to reduce flooding by creating more spaces where water can eventually drain, rather than building up. Also, when we build in cities wechange elevation, sometimes making a space that was a hill flat for a house, this can also create increased flooding as water rushes downward with gravity and then collects in a flat parking lot area.
When precipitation hits impervious surfaces such as pavement, roofs, or vehicles, it can’t soak into the ground, and instead must flow across the hard surface. In the process, this stormwater can pick up any trash, soil, debris, or chemical contaminants that it encounters. Heavy precipitation events can lead to a decrease in water quality by washing these pollutants into local waterways.
To reduce contamination, there is a natural solution already in place, as long as we don’t uproot them: trees. Streamside trees and other plants naturally filter out soil and sediment as rainwater flows over roots, and through leaves and branches. Pollutants bonded to the soil are also removed from the water, such as nitrogen and phosphorus.
Look at this heat map of Atlanta before watching the video on Urban Heat effect, is this concerning to you? Why?
This map is depicting what is called an "Urban heat island," they occur when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that
absorb and retain heat. Asphalt, concrete and other paving materials retain heat rather then releasing it into the atmosphere, this makes cities warmer than more vegetated areas. Plants have
the ability to reduce heat, in cooperation with water collected in soil. This is because they provide shade, deflect radiation from the sun and release moisture since they hold water. [Insert Image]
To solve these problems, we have engineers design Green infrastructure, urban structures such as buildings and roads that are healthier for people, plants and animals because they take into account these different effects. Designing systems that allow water to drain more easily, make use of plants for reducing heat and for filtering water as well as conserving water and energy incorporate main goals of green infrastructure. [Insert Image]
How do you think we can make cities healthier?
