We All Live Downstream
Water sustains all life and that water is recycled and cleaned via ground infiltration, evaporation and various forms of precipitation (snow, sleet and rain). Rain, our most common form of precipitation, provides essential moisture for all living organisms and helps to replenish underground aquifers and maintain the levels of streams, rivers, ponds and lakes.
Unfortunately, in populated places where pavement and rooftops are abundant, rain causes stormwater runoff, which generally has a negative effect on water quality. As rain falls, the water washes away non-point source pollution that drains downstream. Some of those pollutants include trash, chemicals, and petroleum products that have leaked onto streets and parking lots as well as animal waste, fertilizers, pesticides and household chemicals from residential areas.
One thing that can be done to protect water from non-point source pollution and improve its quality is the use of practices that intercept and/or slow stormwater runoff before it enters our waterways. Bio-retention is the most common and easiest way to accomplish this. Bio or plant retention takes several forms including grassy swales, engineered wetlands and rain gardens. These retention areas generally comprise a vegetated buffer strip, ponding area, mulch layer, plants and of course trees, to collect the runoff. These areas are often shaped into basins, depressions and swales. No matter what shape is formed or what plant is installed, the bottom line is to help reduce the volume, slow the speed of and increase the percolation of stormwater runoff, much like what a leafy forest does naturally.
We (the City) have recently implemented such a bio-retention area at the ‘utility square’ along Commerce Alley. Technically, this area is not a true rain garden as it is not a landscaped depression. However, it is capturing a large volume of the parking lot runoff and is landscaped with plants, trees and mulch. Many of the plants are ornamental grasses that can tolerate both wet and dry conditions once established. Among them are purple love grass, dwarf fountain grass, switch grass (native to SC) and muhly grass. Other plants include dwarf abelia, dwarf yaupon holly, dwarf nandina, Natchez crepe myrtle trees and a bald cypress tree, all low-maintenance. Over time as the plants and trees become established, their foliage and root systems will expand and become more effective at filtering pollutants and absorbing stormwater. Albeit this pseudo rain garden is not a large area, but I like to think it will make a little bit of a difference for the folks downstream.
If you have an area in your yard that is low-lying or where stormwater pools, a rain garden may be just the solution needed. The Rain Garden manual, published by Clemson University, introduces the concept of rain gardens and gives detailed instructions on how to properly site, size, construct and maintain a garden. It can be downloaded for free at www.clemson.edu/carolinaclear.
Rain is a natural process critical for our very existence and the quality of that water once it falls in our community depends in large part on how we live and manage our landscapes. With ever changing land uses comes changes in how rain water flows and drains. Anything we can do within our sphere of influence to protect that water benefits us all who live downstream.
Liz Gilland - Camden Urban Forester