Historically, stormwater strategies have included methods to collect, store and move runoff away from urban environments into nearby waterways to prevent flooding in the cities. It was quickly discovered, however, that the systems alone didn’t provide the best solution. Unfortunately, waterways both near and far endured greater volume, velocity and pollutant levels in the runoff.
Modern stormwater management strategies promote practices that work to infiltrate stormwater at its source, which also reduces the stormwater’s contact with pollutants. Modern strategies incorporate vegetated areas such as rain gardens, conservation landscaping and green roofs, which promote percolation of stormwater into the soil as near its source as possible. Thus, reducing the amount of runoff affecting other areas. When stormwater management strategies are designed, incorporated and properly maintained, they also do not provide environs favorable to the breeding of mosquitos.
Cities continued to expand by enlarging natural waterways and lining them with concrete. Unlike the natural waterway, which contained vegetation that reduced the water’s velocity and caused it to flow at greater depths, water flowing through smooth-sided channels moved more quickly and at more shallow depths. These cement canals are ugly, cause worsened flooding downstream, and destroy the habitat of the original natural waterway. Because of these drawbacks, cities soon realized they couldn’t just keep widening the channels to keep up with development.
Cities now require developers to be accountable for the management of the increased runoff caused by their construction and development. Generally, this means that the developers must create methods for on-site stormwater management and storage when needed. Detention and retention ponds are built to take in the stormwaters that flow from streets, parking lots and buildings where it can then be slowly released into waterways; thereby preventing flooding downstream. These processes allow runoff volume to return to the original quantities that existed prior to the construction of the streets, parking lots and buildings. Water pollution is reduced, as well, since suspended particles are given time to settle out.
Onsite storage is a great solution if done properly and responsibly. Stormwaters should not be treated as a problem or a waste product. Stormwater serves a purpose and has done so long before man decided urbanization was important. Stormwater management techniques should consider ways to allow these purposes to be utilized in the design of their systems.
In reality, rainwater is a resource, and natural waterways do more than allow it to discharge. In a natural waterway, the following important functions occur:
- runoff is naturally cleaned and purified by vegetation within the waterway
- runoff that is slowed down by vegetation at the source reduces downstream flooding
- runoff is naturally diverted into the ground (infiltration/percolation), thereby, recharging aquifers and other underground water sources