Understanding and Assessing Impacts
Stormwater is water from groundwater discharge, surface water, precipitation or melting snow and ice that flows across the landscape. Stormwater flows across a property (from rooftops, paved areas, graveled areas, bare soil, lawns, etc.) and gathers along streets, drains, open channels, and sewers in increasingly large amounts, until it eventually discharges into water bodies. In areas served by combined sewer systems, stormwater flows with wastewater to a wastewater treatment facility, where it may lead to a combined sewer overflow. As areas continue to urbanize, stormwater management is especially important due to decreases in natural surfaces and the increases of impervious surfaces like rooftops, sidewalks and asphalt. These surfaces compound the issues with stormwater because they change the permeability of the landscape, preventing stormwater from infiltrating into the ground. Stormwater can pick up and carry pollutants (oil, grease, chemicals, dirt, sediment, nutrients, and pathogens). Without treatment, these pollutants can have a significant impact on downstream watersheds. Stormwater pollution can be significantly reduced with the use of applicable best management practices. A properly designed and functioning stormwater system conveys the stormwater without damage to property, harm to personal health, significant inconvenience to the public, or detrimental environmental effects. However, some recent and historical storm events have caused damage and inconvenience to both public and private property. These storm events have caused problems that generally fall into the following categories: private property flooding, flooding and icing in the public right-of-way, sewer system backups, excessive stormwater in the wastewater system, and degradation in receiving water quality. Scientific evidence indicates that climate change has already contributed to an increase in the severity and frequency of storm events and will continue to do so. There is growing evidence to suggest that regulating site design features to promote control of stormwater at the source is more effective than public infrastructure at lessening effects.