Why do we need raingardens?
Water continually moves from the earth to the atmosphere and back again as part of the water cycle. Whilst water is essential to life, a lack of consideration of where our rainwater goes, and how best it can be managed, can lead to problems of flooding and water quality. Conversely, thinking about how rainwater could be slowed down and held on to in urban areas, can provide benefits for both people and wildlife.
As our climate changes, it becomes increasingly important to consider how best to manage rainwater and respond to the problem of more water falling more quickly and more often.
When talking to others about raingardens, it’s useful to have a general understanding of the water cycle and how human activity, such as development, affects this.
In the natural water cycle, on undeveloped land, precipitation falls and is able to find its way back down into the sea via watercourses, or down into groundwater. The natural landscape and vegetation intercept and slow down water, and there is space for the water to go.
In this urban water cycle, when it rains most rainwater runs off these impermeable surfaces, and down into the drains. The water can flow over hard surfaces much quicker than in the natural water cycle, which leads to the sewer system reaching capacity and a risk of flooding. With heavy rain, combined sewer overflows may send untreated sewage (including all the items thrown down the toilet) into our rivers. Rainwater also picks up contaminants from roads and roofs.
Why not just build bigger sewers so there is somewhere for the water to go?
We could build bigger sewers, but this is expensive and may not be the best solution. Rainwater is relatively clean and doesn’t need to be sent to a sewage works before it finds its way back to the river. Building raingardens also gives other benefits to people and wildlife.
Raingardens can provide people with beautiful places to sit, walk through and look at. They provide a space for nature, giving insects (including pollinators) and birds a home and food. The plants which grow in raingardens help improve air and water quality. By slowing down the rainwater, and stopping it getting to the sewers so quickly, raingardens help to reduce flooding and protect our rivers from combined sewer overflow.