Stormwater management

DEFINITION: Methods of containing and channeling water from precipitation that flows over land or impenetrable surfaces and does not percolate into the ground

When stormwater is uncontrolled, water resources may be wasted and destructive flooding may occur; in addition, pollution carried by stormwater can contaminate bodies of water and endanger human and animal health. Stormwater management systems are designed to minimize the environmentally destructive potential of precipitation runoff.

Stormwater management, which has its roots in ancient Greek and Roman cultures, has evolved into the vast systems now present in all developed and many developing nations. The management of stormwater has become increasingly important over time with human development, as the impervious surfaces of buildings, roads, parking lots, and so on do not allow rainwater and snowmelt to penetrate into the ground, resulting in much more than occurs on undeveloped land. All developed and many developing nations have laws in place that set standards for stormwater management.

Pollution and Uncontrolled Runoff

Stormwater management is necessary to address the problem of water caused by runoff. Polluted stormwater runoff from impervious surfaces such as roads and roofs, as well as from agricultural fields, is a major source of around the world. Water flowing over human-built surfaces picks up pollutants such as gasoline, oil, trash, and heavy metals (mercury, lead, cobalt, copper, and zinc). Water flowing over lawns and farm fields collects nitrates and phosphates from the fertilizers used on these surfaces.

In the United States, the pollution of waterways became a nationally recognized issue in June, 1969, when the Cuyahoga River, flowing through Cleveland, Ohio, on its way to Lake Erie actually caught fire because it was so polluted. At that time, Lake Erie had become a victim of eutrophication, a process in which an increase in chemical nutrients alters plant growth in an ecosystem. Algae became the dominant plant species in the lake and absorbed all the oxygen in the water, killing most of the native fish and other aquatic species. For decades, far more nutrients entered the lake than it could handle; the main culprit was phosphorus, a component of fertilizers and detergents. Heavy metals and pesticides also contributed to the pollution. Fish that managed to survive in the lake were unfit for human consumption.

Another problem addressed by stormwater management is uncontrolled runoff, which not only results in the of a valuable resource but also can cause extensive damage. When the amount of water generated by rain or snowmelt exceeds the capacity of waterways, flooding occurs. Floods are among the most frequent of all forms of natural disasters, and they are also among the most costly in terms of human and animal deaths, destruction of structures and habitats, and soil erosion.

Conditions that result in flooding include heavy or steady rains that last hours or days; such rains can exceed the capacity of the ground to absorb the water, and after the ground is saturated the excess flows to lower areas. In areas where forest or brush fires have recently taken place, denuding the landscape of plants that absorb and stabilize the soil, subsequent rainfall can result in flooding, often accompanied by mudslides.

Methods of Management

Methods of stormwater management address the problems of pollution and uncontrolled runoff. Bodies of water become contaminated by both pollution and nonpoint source pollution. Point source pollution occurs when pollutants enter a waterway through a specific entry point, such as a drainage pipe discharging into a river. This type of pollution is much more controllable than nonpoint source pollution, which originates from a variety of diffuse sources that are difficult to identify; pollution from stormwater is a form of nonpoint source pollution.

An example of pollution control involving stormwater management can be seen in the situation that was present in Lake Erie and the other Great Lakes during the 1960s. Recognition of the levels of pollution in the lakes led to the Great Lakes Water Quality Agreement (GLWQA), signed by the United States and Canada in 1972, and the US federal Clean Water Act, also enacted in 1972. The GLWQA stressed the reduction of the amounts of phosphorus (then an ingredient in many laundry detergents) entering Lake Erie and Lake Ontario through stormwater runoff, and in 1977 maximum allowable levels of were set by an amendment to the agreement. (Phosphorus was subsequently banned from detergents in both the United States and Canada.) By 2010 the phosphorus level in Lake Erie was found to be below the maximum allowed by the GLWQA, and the of the lake had also abated. Despite these improvements, Lake Erie still has a number of problems, including contaminated sediments.

Ideally, stormwater runoff should be not only channeled to prevent damage but also collected for future use or decontamination. Stormwater collection methods range from rooftop cisterns used to collect and store rainwater for household uses to systems that channel stormwater to reservoirs that can supply water to large populations. Retention basins can both control runoff and allow treatment of the contained water. Stormwater is usually channeled to a retention basin from storm drains. Water entering the basin is restricted from flowing outward unless a major storm event occurs. These basins are often landscaped with varieties of plants that improve the water by removing excess nutrients and other pollutants. Another concept for runoff control is the swale or bioswale, which is a wide and shallow ditch designed to maximize the time water spends within it. Plants in the swale absorb and break down pollutants.

Even small stormwater runoff control systems can be effective. One example is the rain garden, which is a planted area designed to collect runoff from nearby impervious surfaces such as parking lots, driveways, roofs, and walkways. The hardy local plants used in the rain garden help the soil to absorb the runoff and any pollutants it contains.

Regulations

All developed nations and some developing nations have well-established stormwater management policies. In the United States, the Environmental Protection Agency (EPA) oversees stormwater management under the provisions of the Clean Water Act. The EPA’s National Pollutant Discharge Elimination System (NPDES) regulates stormwater discharges from municipal storm systems, construction activities, and industrial activities. In addition to implementing NPDES requirements, many state and local governments in the United States have passed their own laws concerning stormwater management.

The treaty that created the European Union established environmental policy as one of the functions of that body. The aims of this policy are to protect and improve the quality of the environment, to protect the health of the population, to promote the careful and rational use of natural resources, and to promote measures at the international level to overcome regional and broader-scale environmental problems. By the early years of the twenty-first century, all Western European nations had adopted legislation setting standards for the collection, treatment, and disposal of wastewater.

The stormwater policies of many Asian nations, including Japan and the People’s Republic of China, are continually evolving. Australia, which has a well-developed stormwater policy, faces particular challenges because water resources are scarce on the Australian continent.

Stormwater management systems are generally much less advanced in developing nations than they are in the developed nations. In the cities of developing nations, the urban poor are most affected by inadequate stormwater management. Poor communities are often located on low-lying land, which is prone to flooding, or on steep hillsides, where heavy storms can wash away flimsy structures.

Bibliography

Akan, A. Osman, and Robert J. Houghtalen. Urban Hydrology, Hydraulics, and Stormwater Quality: Engineering Applications and Computer Modeling. Hoboken, N.J.: John Wiley & Sons, 2003.

Committee on Reducing Stormwater Discharge Contributions to Water Pollution. Urban Stormwater Management in the United States. Washington, D.C.: National Academies Press, 2009.

Davis, Allen P. Stormwater Management for Smart Growth. New York: Springer, 2005.

Debo, Thomas N. Municipal Stormwater Management. 2d ed. Boca Raton, Fla.: CRC Press, 2002.

Gribbin, John E. Introduction to Hydraulics and Hydrology with Applications for Stormwater Management. 3d ed. Clifton Park, N.Y.: Thomson Delmar Learning, 2007.

Grigg, Neil S. Water, Wastewater, and Stormwater Infrastructure Management. Boca Raton, Fla.: CRC Press, 2002.

James, William. Advances in Modeling the Management of Stormwater Impacts. Boca Raton, Fla.: CRC Press, 1997.

Mays, Larry. Stormwater Collection Systems Design Handbook. New York: McGraw-Hill, 2001.

Sevbert, Thomas A. Stormwater Management for Land Development: Methods and Calculations for Quantity Control. Hoboken, N.J.: John Wiley & Sons, 2006.

"Stormwater Management Research." US Environmental Protection Agency (EPA), 27 Feb. 2024, www.epa.gov/water-research/stormwater-management-research. Accessed 23 July 2024.

Zu, Hanwen, Mark Randall, and Ole Fryd. "Urban Stormwater Management at the Meso-Level: A Review of Trends, Challenges and Approaches." Journal of Environmental Management, vol. 331, 1 Apr. 2023, doi.org/10.1016/j.jenvman.2023.117255. Accessed 23 July 2024.