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t 5.2 IMPACTS TO WETLANDS With the passage of wetland protection legislation, and construction of ponds for runoff management, the rate of degradation from urban development has been greatly slowed. However, with intensive land development, agricultural production, and housekeeping practices in developed areas, degradation of wetlands continues. The focus of recent wetland legislation, policy, and practice has been to preserve the functions, values, and overall quality of wetlands by minimizing poor water quality and unmanaged quantities of runoff associated with agro- urban impacts. 5.2.1 Water Quality Impacts Water quality plays a significant role in the overall quality of a wetland. When the quality of incoming water declines, the plant community may degrade to fewer of species and retain only species tolera_nt of high nutrient and sediment loads. A degraded plant community results a less valuable ecosystem in terms of biodiversity, habitat, and aesthetics. There are two primary factors that affect the quality of runoff entering a weiiand, and therefore to overall water quality within the wetland: l . phosphorous, as the primary nutrient of concern 2. sedimentation, resulting from erosion of soil. 5 .2.2 Water Quantity Impacts Recent surface water management plans have protected wetlands from nutrients but not from fluctuation of water elevation (bounce) or duration of inundation. In fact, it was common to use wetlands to reduce flooding potential by sizing pipes to maximize bounce and duration. The findings of the (State of Minnesota) Storm Water Advisory Group were published in a document called Guidance For Evaluating Urban Storm Water and Snowmelt Runoff Impacts To Wetlands (1994). The findings indicated that there is a broad range of tolerance to bounce and duration among different wetland types. And to a lesser extent, the range of tolerance can be attributed to the charactecistics and quality of a given wei1and. Some wetlands (e.g., bogs and fens) are sensitive to any disturbance and will show signs of degradation with even low-level inputs of runoff. Conversely, some wetlands (e.g., floodplain forests) are better adapted to handle fluctuating water levels oft~n associated with runoff. City of Orono 5-2 t:::,,~,,..1!3 JA/-.1-,.., .. u~-------• '""'--