Urban created wetlands as an alternative to urban ponds: An analysis of environmental and economic benefits

Scope and method of study. The purpose of this study was to examine the environmental and economic benefits of constructing urban wetlands instead of urban ponds as a management alternative to indefinite aeration, repeated treatments of herbicides and pesticides, turbidity treatments, and basin and shoreline sediment maintenance. Four urban stormwater ponds, with varying levels of maintenance, and two created wetlands in central Oklahoma were monitored seasonally for representative water quality parameters and avian usage. Baseline environmental data also included soil analysis and hydrology. Using benefit transfer, the economic value of the urban ponds and created wetlands was estimated. Net present value (NPV) was calculated to assess the value of different maintenance strategies. Aerial photography and water depths along transects were used in conjunction with a geographic information system to estimate erosion-potential of shoreline slopes, area available for wetland planting, and to calculate a Landscape Development Intensity (LDI) index from percent urban, agricultural, and undeveloped land surrounding each site.; Findings and conclusions. Avian usage was significantly higher in the created wetlands than the urban ponds. The water quality in the urban created wetlands was equal or better than the urban ponds monitored in this study. High levels of nutrients in stormwater runoff entering the sites in addition to high LDI suggests all the sites have significant amounts of stormwater pollution stress. The created wetlands had higher benefit value and NPV per acre per year than the urban ponds. Hypothetical augmentation of the urban ponds with wetland plants increased the NPV of these ponds by providing greater wildlife and water treatment benefit and thus is more cost-effective than traditional maintenance practices.