With the amount of rain falling during the heaviest storms increasing by 20 percent over the last century, cities have good reason to be preparing for lots of rain this summer.
While the traditional method of a storm drain on the street leading to a pipe system may be enough for smaller amounts of rainfall, these systems can become overwhelmed in large-scale rain events. They also don’t account for pollution and other issues.
To improve their rain management systems, low-lying areas are combining traditional storm drain systems with other, innovative solutions.
Using the natural environment to help manage rainwater is one increasingly common solution. These devices include rain gardens, bio-swales, grass filter strips, detention ponds and artificial wetlands.
Rain gardens are placed slightly below ground level, so they collect water as it runs by. They also double as an attractive lawn feature.
Detention ponds and wetlands work similarly. Detention ponds collect water in a small pool, while wetlands generally take up a larger surface area, but are shallower and also include wetland plants. These two solutions, along with rain gardens, help prevent flooding and also use the vegetation to filter pollutants out of the water.
Grass filter strips and bio-swales are designed specifically to remove pollutants from runoff. Strips are thin vegetated spaces that filter water as it flows through. Vegetated swales are a series of channels that include plants to filter water.
While natural landscapes can usually manage stormwater on their own, man-made ones can not. Infiltration devices improve man-made landscapes for better water management. They allow water to seep through the surface to be stored underground or eventually evaporate into the air in areas where it usually couldn’t.
Paved areas, such as parking lots and roads, don’t typically allow rainwater to sink into the ground. Porous pavement, however, changes that. It consists of many small pieces and includes small empty spaces, so water can get through. Pavement might also intentionally include small strips of empty spaces to allow grass to grow.
Infiltration trenches also store water. Often, water will pass through a swale or filter strips before entering the trench, which is filled with stones. Over a few days, the water sinks into the spaces between, and then into the soil, where it is filtered and stored underground.
In certain situations, more high-tech solutions may be needed. Municipalities sometimes use water jetting and vacuum machines to keep stormwater pipes and drains clean.
The blasts of water can dislodge debris and dirt, and high-powered vacuums pull the debris out. Some municipalities use combination machines that feature both water jetting and vacuum capabilities, powered by a hydrostatic drive.
This ensures the highest volume of water possible traveling through the pipes, and makes the water that comes out the other end cleaner, which reduces pollution.
Land Use Planning
Taking stormwater management into account when designing and developing communities can help prevent it from becoming a problem, even in the case of heavy rainfall.
As areas become developed, natural groundcover is often replaced with pavement or another non-porous surface. Some areas require a certain amount of green areas or porous pavement in new developments, especially around waterways.
Curbs and gutters move water as quickly as possible into a storm drain but allow no time for infiltration or the removal of pollutants. The Environmental Protection Agency recommends replacing curbs and gutters with swales or filter strips.
Reducing and managing pollution is another preventive measure that can improve stormwater management.
Using less road salt, artificial lawn fertilizers and other pollutants can make the water that runs into rivers from storm drains much cleaner. Not storing these types of chemicals outside, or covering them if they are stored outside, can help as well.
Homeowners can also take steps to control runoff. Planting vegetation where water runs off the roof or driveway can help remove pollutants from water before it makes it to the storm drain.
When municipalities promptly fix leaks in pipe systems and avoid spills, they help prevent pollution as well.
As stormwater becomes a more serious problem, especially in low-lying areas, new techniques will have to be integrated into stormwater management systems. Solutions such as green infrastructure, infiltration devices and pipe-cleaning machinery can help prevent flooding and the pollution of waterways.