Essay: More on this visualization

Urban sprawl has different patterns in different regions. In the western United States, such as around Phoenix, Arizona, the haphazard, low-density spread of development has accompanied rapid increases in population. In the eastern United States and other areas, both the population and the per capita use of land are on the rise. With more people using more land, natural resources are increasingly stressed and wildlife habitat is eliminated. Urban sprawl also changes the quality, quantity, and timing of water delivery to streams, rivers, and estuaries. This visualization illustrates how urban sprawl affects the nation's largest estuary: the Chesapeake Bay and its tributaries.

Urban sprawl replaces soil and vegetation with impervious surfaces such as pavement and rooftops. This disturbs waterways. Normally, rainwater percolates slowly through the bare earth to enter the water table. Impervious surfaces stymie this process, channeling rainwater over land. Coursing aboveground, the water accumulates oil, pesticides, and other pollutants before it eventually joins streams. When sprawl affects large portions of a watershed, pollution and river channel erosion can prevent aquatic life from thriving.

These processes deliver chemicals from several Mid-Atlantic states to the Chesapeake Bay and associated waterways. Federal and state authorities are seeking to minimize the impact of urban sprawl on the Chesapeake Bay ecosystem by concentrating and reducing development. One aim of these efforts is to facilitate water movement into the ground rather than over impervious surfaces.