Methods to Reduce Urban Runoff (College Board AP® Environmental Science): Flashcards
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Define urban runoff.
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Cards in this collection (17)
Define urban runoff.
Urban runoff is rainwater that flows over impervious surfaces, such as roads and buildings, instead of infiltrating into the soil.
Why does excess urban runoff increase flood risk?
Excess urban runoff increases flood risk because water cannot soak into the ground, so it accumulates quickly on surfaces and overwhelms storm drains, rivers, and low-lying areas.
Reducing urban runoff helps prevent flooding, improves water quality, and supports recharge.
Reducing urban runoff helps prevent flooding, improves water quality, and supports groundwater recharge.
Define permeable pavement.
Permeable pavement is pavement made from materials that allow water to soak into the ground, such as porous asphalt, pervious concrete, and interlocking pavers.
True or False?
Permeable pavement is well suited to very heavy-traffic surfaces such as highways.
False.
Permeable pavement is not suitable for very heavy-traffic surfaces such as highways, and its pores can clog with sediment over time.
How does increased use of public transportation reduce pollution in urban runoff?
Fewer cars on the road means less oil and heavy metal pollution is washed into runoff.
Define green roof.
A green roof is a set of layers of soil and vegetation installed on the roof of a building.
How do green roofs reduce stormwater runoff?
Plants on green roofs absorb rainfall through their roots and release it slowly through evapotranspiration, trapping rainfall on the roof at source.
As well as reducing runoff, green roofs insulate buildings and reduce the urban effect.
As well as reducing runoff, green roofs insulate buildings and reduce the urban heat island effect.
What must be done to a building before a green roof can be installed?
The building needs structural reinforcement to support the added weight of the green roof.
Define rain garden.
A rain garden is a shallow planted depression that collects runoff from roofs, driveways, or roads, where native plants and porous soil absorb and filter the water.
True or False?
Rain gardens can absorb the runoff from even the heaviest storms.
False.
Rain gardens have limited capacity and are easily overwhelmed in heavy storms. They also perform poorly on heavy clay soils with low natural infiltration.
Define retention pond.
A retention pond is an engineered pond that holds stormwater before it is gradually released into nearby waterways.
How does a retention pond improve the quality of water leaving a site?
Holding the water in the pond allows suspended sediments and pollutants to settle out before the water leaves the site.
Why are retention ponds difficult to use in dense urban centers?
Retention ponds are difficult to use in dense urban centers because they require a significant land area.
How do trees reduce urban runoff?
Tree foliage intercepts rainfall, slowing how fast it accumulates on impervious surfaces, and tree roots improve soil structure so the soil retains more water.
How does building up, not out, help reduce urban runoff?
Building taller instead of sprawling reduces land consumption, which limits the spread of impervious surfaces and leaves space for green infrastructure, parks, and wetlands that absorb runoff.
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