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How does urbanization contribute to flooding?

Urbanization contributes to flooding in that urban areas have less porous ground and vegetation available to soak up water.

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Urbanization often has the effect of increasing both the frequency and severity of floods. This is due to several factors.

First off, cities are characterized by the creation of impermeable surfaces. Roads, buildings, and pavement prevent rainwater from being absorbed into the ground. Without the features of urbanization, much of...

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Urbanization often has the effect of increasing both the frequency and severity of floods. This is due to several factors.

First off, cities are characterized by the creation of impermeable surfaces. Roads, buildings, and pavement prevent rainwater from being absorbed into the ground. Without the features of urbanization, much of this water would be absorbed into the soil and make its way to an aquifer or a natural waterway. However, in places where the ground has been covered with impermeable surfaces, rainwater stays on the surface, which contributes to flooding.

Furthermore, outside of urban areas, vegetation will also soak up excess water. Cities have much less vegetation to perform this action. This results in more water runoff finding its way to urban streams and waterways, which can quickly become oversaturated during heavy rains or snowmelt.

Also, waterways are usually changed and engineered to accommodate urban development. Usually, they are made narrower to allow for more buildings and bridges to be built. This reduces the carrying capacity of these waterways, making it much more likely for water to overflow their banks during heavy precipitation and runoff. To make matters worse, urban waterways are usually straight. This increases the water's velocity, which leads to more erosion. Such erosion can damage roads and foundations, leading to an increase in damage when there is a flood.

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