Avoided Runoff estimates the number of gallons of stormwater runoff each year that is avoided because tree canopies catch rainfall and trees return some water to the atmosphere through evaporation and transpiration.
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Surface runoff can be a cause for concern in many urban areas, as it can contribute to pollution of streams, wetlands, rivers, lakes, and oceans. During precipitation events, some portion of precipitation is intercepted by vegetation (trees and shrubs), while the remainder reaches the ground. The portion of the precipitation that reaches the ground and does not infiltrate into the soil becomes surface runoff (Hirabayashi 2012). In urban areas, the extensive extent of impervious surfaces increases surface runoff.
Urban trees and shrubs, however, help reduce surface runoff. Trees and shrubs intercept precipitation, while their root systems promote infiltration and storage in the soil. Avoided runoff is estimated based on local weather data from the Purdue weather station at the time of calculation.
Ecosystem service estimates were generated using i-Tree Eco, a peer-reviewed urban forest assessment tool developed by the USDA Forest Service and partners. Learn more at i-Tree Eco.
