2010 | Dr. Susan Day, Virginia Tech
Trees are an important component of successful low impact development (LID) and stormwater mitigation practices, yet, ironically, trees are often being removed or severely damaged to create these very same stormwater systems. Many local governments, especially those near sensitive water bodies, require the implementation of vegetation-based stormwater management systems such as bioswales, infiltration trenches, and rain gardens, often called “stormwater best management practices” or BMPs. In theory, these vegetation-based solutions acknowledge the extraordinary effectiveness of trees in stormwater mitigation, including reduction of runoff and movement of N and P into waterways. However, in practice, arborists are reporting that large and valuable trees are being regularly removed to make way for bio-engineered structures designed to manage stormwater. In addition, when trees are incorporated directly into infiltration trenches or rain gardens, conflicts arise such as concerns over root intrusion into pipes and loss of stability due to root confinement. Thus, many LID sites focus on grassland or vegetative swales to mediate stormwater issues and do not utilize the many benefits that trees could provide in these systems. In addition, installed trees may be short lived and established trees may be destroyed when site soils are graded to control water flow. It is essential that we understand and resolve these conflicts so that we can maintain urban forest canopy and protect large stature trees in the face of mounting concerns and regulations concerning urban runoff reduction.
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