The Effect of Watershed Urbanization on River Hydrology and Ecology: Assessing the Use of Population Density as an Estimate for Percent Impervious Cover

Abstract

Population distribution in the United States follows a pattern of development known as urban sprawl. The trend of urban sprawl and its associated development of pervious land cover types such as natural and agricultural land to impervious land cover types such as roads, parking lots, and structures has had significant impacts on watershed hydrology and river ecosystems. As a watershed becomes increasingly developed, the discharge of the watershed increases and in effect the frequency and intensity of flood events increases. Using the Des Plaines River Water-shed as a case study, a model was made to demonstrate that the use of population density as a measure of percent impervious cover is a viable proxy to show its correlation with river discharge. Population densities of the watershed were correlated against the watershed’s discharge for the decades between 1940 and 2010. The model indicated with a significance value of < 0.001 and an R2 value of 0.92 that population density within the Des Plaines River Watershed was positively correlated with the discharge of the Des Plaines River. The use of population density in this model as a proxy for percent impervious cover when land cover data is unavailable provides a robust approach for revealing how variations in level of development impacts watershed hydrology.