Distribution of stormwater ponds in relation to land use in a suburban watershed
Urbanization is a significant anthropogenic force that can degrade environmental quality. Urban development significantly alters the hydrology, flow, and quality of rivers lakes and streams. Stormwater ponds, which are designed to mitigate the impacts of urban land-use on downstream water bodies, can contribute significantly to aquatic ecosystems in some urban watersheds, but ecological research on these systems is lacking. The objective of this study was to determine the distribution of stormwater basins and their associated land-use in an urbanizing suburban watershed. A 2009 GIS database of land-use in the Econlockhatchee River Watershed in east-central Florida, acquired from the St. Johns River Water Management District, included 1,587 features designated as reservoirs or ponds. Through visual interpretation of aerial photographs, features not considered stormwater ponds (e.g. farm ponds, borrow pits) were eliminated, resulting in 1,368 stormwater detention ponds in the watershed. A near table of 663 of these ponds was generated with a 100 meter radius to create a subset of ponds that would not overlap when they were clipped with a 50 meter buffer. Surrounding land-uses within the 50 meter buffer of these selected ponds were categorized as a proxy for defining the mitigated land-use for which the ponds were built.
The total areal extent of stormwater basins in the Econlockhatchee watershed was 1,611 hectares, equaling 1.3% of the total watershed, which was much greater than the total areal extent of natural lakes (1,111 ha) in the watershed. Stormwater ponds thus contribute significantly to open water habitat in this region. The 50-m buffer areas of the subsampled stormwater ponds contained eleven different land-use groups dominated by urban land use covers (63.4%): 43.7% was residential; 14.7% was roadway; 2.7% was commercial and services; and 2.3% was institutional. This analysis indicated that the majority of stormwater ponds in the watershed were built to mitigate impacts of residential development. These preliminary data were used to randomly select ponds in residential, roadway, and institutional areas, in a larger study investigating how different urban land uses influence ecological conditions and management of stormwater ponds. The institutional land use was chosen over the commercial and services category because both were similar in size and access for institutional sites is easier to obtain. The results will increase our understanding of urban land-use impact on water quality and may inform effective natural resource management and urban planning for stormwater basins.