The character of urban water bodies in the United States

Background/Question/Methods

A comprehensive understanding of urban ecosystems requires integrating water bodies into the conceptual framework of developed watersheds.  The size, shape, and connectivity of water bodies (lakes, ponds, and wetlands) can have important effects on ecological communities and ecosystem processes, but how these characteristics are influenced by land use and land cover change is not known.  Intensive alteration of water bodies during urban development, including construction, burial, drainage, and reshaping, may select for certain morphometric features and influence the types of water bodies present in cities. We used a database of over 1 million water bodies in 100 cities across the conterminous United States to compare the size distributions, connectivity (as intersection with surface flow lines), and shape (as measured by shoreline development factor) of water bodies in urban land covers and land uses to water bodies in undeveloped land cover. 

Results/Conclusions

Water bodies in urban land covers were dominated by lakes and ponds, while reservoirs and wetlands comprised only a small fraction of the sample.  Water body size and shape distributions were shifted toward larger features, and less tortuous shorelines, relative to surrounding undeveloped land.  In addition, the number and area of water bodies that intersected surface flow lines (i.e. streams and rivers) was lower in urban areas than surrounding undeveloped land by, from 83% connected in the undeveloped land to 18% connected in the high density urban land cover. The larger size and reduced surface connectivity of urban water bodies may increase the relative importance of internal dynamics.