Stormwater
From Water Wiki
Stormwater is rainfall that does not either infiltrate into the ground or evaporate. Also called runoff, it is water that flows over the surface of the ground until either sinking in or reaching a waterway.
Runoff picks up substances as it travels over the ground. When runoff flows over parking lots and roads, it picks up motor oil, dirt, and brake dust. When it flows over yards and lawns, it picks up pet waste, fertilizers, and pesticides. These pollutants are carried directly to the nearest creek, stream, lake, river, or beach. Only recently have we begun to treat stormwater to try to remove some of these pollutants. In most areas, stormwater receives no treatment whatsoever. In addition to making drinking water treatment more expensive and difficult, these pollutants cause algae blooms, fish kills, beach closures, and shellfish harvesting restrictions.
Urbanization also changes the HYDROLOGY of a watershed. Urbanization increases impervious cover: roads, rooftops, parking lots, driveways, and sidewalks and other hard surfaces that prevent stormwater from sinking into the ground. Because less of it sinks into the ground, more rainfall is converted to runoff. This larger volume of runoff can carry even more pollutants, and it travels faster over impervious cover than vegetation. The larger volume of runff, travelling more quickly, degrades streams because the greater force of it erodes stream banks, deepens and widens stream channels, and carries away the debris that aquatic wildlife need for shelter.
More runoff also means that property downstream is more prone to flooding compared to before the unbanization took place.
North Carolina has regulated stormwater quality in some areas (the coast, water supply watersheds) since the late 1980s. But the federal NPDES Phase II rules that appeared in 2000 greatly expanded the regulation of stormwater in the nation’s urbanized and urbanizing areas. Jurisdictions that are covered by Phase II rules are required to have public education programs, public involvement in stormwater planning, good housekeeping practices at their own facilities, a plan for finding and eliminating illicit discharges of stormwater, and (most difficult to administer) a permit program that ensures the creation and long-term maintenance of best management practices (BMPs) to manage stormwater on private developments larger than one acre.
In at least some parts of North Carolina, decisions about stormwater management could have important consequences for water supply. Stormwater BMPs in the coastal plain and the sandhills can be take advantage of the high permeability of sandy soils to maximize infiltration of stormwater into groundwater (where the water table does not preclude additional saturation). In the Piedmont and Mountain regions, stormwater BMPs still may encourage infiltration, but the clay soils and steep slopes complicate design, installation, and maintenance. Properly done stream, buffer, and wetland restoration projects (using, for example, Rosgen's designs) help restore some infiltration capacity lost due to historic development that failed to adequately manage stormwater quantity.
"Stormwater” has important legal synonyms: “urban runoff” was used widely in the 1960s through 1980s, and earlier legal cases sometimes used “diffuse surface water.”
The General Assembly enabled
municipalities and counties to create stormwater utilities in the 1980's. Mecklenburg may be the only county in NC to use this authority to create a countywide stormwater utility. The county manages major stormwater and stream restoration projects; municipalities handle minor drainage projects. Mecklenburg County also manages floodplain and park, recreation & greenway programs which compliment stormwater management. Water was abundant and cheap in the 1980's. Stormwater was a problem not a resource.
Municipalities have been in the stormwater business for hundreds of years. We used to
call it drainage. Their public works or street departments built curbs, gutters, streets and storm drains. They drained wetlands and channelized streams. Most (all?) municipalities placed their new stormwater utilities with their "original" stormwater program -- drainage -- in their public works departments. This aids in mapping and managing the existing stormwater/drainage system. Most stormwater fees are low, primarily cover managing the existing stormwater system, and don't generate adequate capital funds for rainwater harvest, stormwater reuse, stormwater treatment and stormwater retrofits. Stormwater managers in local public works departments often have to compete for limited funds and attention with street and highway projects. Although water and wastewater rates are also generally low in NC, water and wastewater utilities have more revenues for planning and water resource management. ($30/month raises a lot more revenue than $2-4/month.) Water and wastewater utilities plan to invest millions in developing new soures of water, including new storage, reclaimed water and efficiency. Stomwater managers should be at the water options table. The costs and benefits of rainwater harvesting and stormwater reuse systems compare favorably with the development of other "new" sources of water. Muncipalities should be able to easily compare the costs, benefits, risks, etc of their water options so that they select the most cost effective solutions and so that they develop a resilent water system. Municipalities should improve integration of their stormwater utilities with their drinking water and wastewater utilities and may want to consider transferring stormwater from streets and public works to water and wastewater. Muncipalities would also be better able to compare the costs and benefits of stormwater and wastewater water quality improvements.
There is a longer history of stormwater management in the coastal areas of NC.
