When rain falls on a field, woodland or backyard, it follows what scientists call the natural hydrologic cycle. First, rain is absorbed by the soils, then it becomes available to plants for uptake and growth. Some of it evaporates back into the air from the plant leaves, and the rest moves downward in the soils, being filtered as it goes, until it replenishes our groundwater supplies, where we get most of our drinking water. Some of the water makes its way through the ground to surface waters like ponds, rivers, and the ocean, where eventually the water will be evaporated back into the air, form clouds, and become rain again. What is noteworthy is that very little rain over vegetated land ever runs off directly into surface waters.
In this way, rain is a valuable resource that provides clean water to drink and keeps our soil full of nutrients, our food crops growing, and our fishing opportunities plentiful.
When rain falls on impervious surfaces like sidewalks, roads, even rooftops, it becomes “stormwater.” For a long time now, urban communities have managed stormwater by collecting it in gutters, downspouts, trenches and roadway storm drains and channeling it back to surface waters thru underground systems. This extensive amount of infrastructure bypasses the natural water quality treatment provided when rain filters through the soils, and instead collects and concentrates pollutants picked up from the roofs and roadways, like oils, cleaners, pesticides, bacteria, etc.
Pipe and drain systems also convey the water away very quickly, resulting in concentrated flows of water being discharged all at once into streams and lakes. This storm pulse can overwhelm the natural abilities of the streams and cause both flooding and scouring, like a pressure washer, eroding soil and sand away from river banks and beaches. In areas where we have removed the natural plant buffers along rivers and estuaries, this scouring effect becomes even more intense, even jeopardizing nearby homes. The sand and soil that ends up in the water from this erosion can be delivered to sensitive fish habitats miles downstream or on the coast, leading to degradation of water quality, wildlife, and fisheries far beyond the local area.
In these ways, rain has become stormwater and now needs to be actively managed in order to protect water from getting polluted, protect soil from washing away, and prevent damage to homes, buildings, and roads.
The older pipe/drain infrastructure of stormwater management can be expensive to maintain, and many cities across the country have been faced with mandatory upgrades, replacements, or full redesigns of this infrastructure as weather events intensify and as development continues to grow. Many cities across the country have adopted stormwater taxes for landowners. Individual homeowners and businesses can help by filtering and delaying stormwater before it leaves their properties, thus minimizing the burden on city taxes.
In urban environments, impervious surfaces like roads are an important part of our lives. But we can incorporate strategically located pockets of planted land to replace the functions of the natural hydrologic cycle. Retrofitting our urban communities with systems like raingardens or greenstreets or bioretention ponds adds beauty and function to our landscapes! Our next article in this series will show you how these green infrastructure solutions work!
The town of Westerly has been very proactive in seeking funding to manage their stormwater issues with resilient solutions that balance benefits to both the town’s built infrastructure and to the critical environmental services described above. Westerly is partnering with the Southern Rhode Island Conservation District to design and manage these projects and educate the public about the benefits. For example, the Canal Street wastewater pump stations will receive upgraded retaining walls to ensure their protection against flood damage. Springbrook Road will receive a raingarden design which allows the stormwater to slow down and soak into the ground without impacting the neighborhood. A Green Infrastructure Demonstration Project along downtown Main Street is underway to showcase the many benefits of this approach, including streetscaping and beautification, water quality improvements, flooding improvements, and revitalization of the area.
The writer is a conservation specialist with the Southern Rhode Island Conservation District.