Urban Forestry & Stormwater Management

Using trees to enhance stormwater management efforts

High intensity land use patterns and increasing pressure on water resources demands creative stormwater management. Trees dissipate the energy of falling raindrops to help prevent erosion and buffer intense rainfalls. Urban tree roots have the potential to penetrate compacted soils and increase infiltration rates in open space areas, stormwater basins and subsurface stormwater storage (structured soil). Uptake of water from trees limits the volume of runoff discharged downstream, and their canopies offer interception of rainfall and shading (cooling) in an urban environment. Trees also absorb nutrients that could otherwise run off to local receiving waters.

This fact sheet provides an overview of the benefits of protecting existing trees and planting new trees in stormwater treatment practices of new development or redevelopment sites and includes activities that can be implemented by an MS4.

Benefits / Pollution Reduction

Urban forestry strategies can help satisfy many of the MS4 stormwater management requirements in a cost effective manner. Trees, forests, and other natural areas effectively manage water through interception, evapotranspiration, and infiltration. Together, these processes can significantly reduce peak stormwater rates and volumes, naturally filter runoff, enhance ground water recharge, stabilize base flows and reduce erosion in streams.

Trees also take up nutrients and various pollutants through their root systems. A study of the City of Fayetteville, Arkansas, estimated that increasing tree canopy from 27 percent to 40 percent would reduce stormwater runoff by 31 percent (American Forests, UEA of Benton and Washington Counties, Arkansas, 2002).

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