How the humble tree can help tackle flooding

Trees are fantastic, we all know that. Some of our favourite childhood memories are in trees- either picking fruit from them, climbing them, or swinging on ropes from them. 

They also absorb carbon, making tree-planting a great way to slow climate change, which means they’ll help reducing climate impacts like flooding in the long-term. But did you know that trees have a double purpose in tackling flooding: they can also be used to manage rivers? This leads us to the question, how is flooding controlled?

There are two methods used to stop flooding: soft engineering and hard engineering. Hard engineering methods mean building man-made structures that stop the natural processes that lead to flooding. Soft engineering methods tend to work with these natural procedures. We’re working in Wolverley, Worcestershire on  tree-planting - a soft engineering method that is great at controlling floods. Here is how it works. 

Trees reduced flood risk from the top to bottom. Let’s start at the top: leaves reduce flooding in two ways. Firstly, if raindrops land on leaves, they sometimes evaporate straight into the air- so less water reaches the ground. 

Secondly, the leaves intercept rainfall, slowing the rate that water flows into rivers. This reduces flood risk as floods are essentially caused by too much water entering rivers or streams in a too short space of time. 

Brilliant, right? And that is just the leaves! 

The roots of a tree also have a vital job in reducing flooding. The roots of a tree dig deep and this creates loads of little roads and passages in the soil. When water reaches the ground, it drains into all the spaces created by the root system. So less water actually reaches the river, as loads more water can be stored in the soil. 

The other role of the roots is a little more complicated. Roots act as a kind of net, holding all the soil in place. This means less soil enters the river. Soil in the river settles on the river bed and shrinks the size of the river so there’s less space for the water. Basically, trees ensure that rivers stay big, and can continue to hold lots of water. Small water bodies are much more likely to be overwhelmed, and flood.

Trees are a great way to combat flooding. Plus - they’re gorgeous! That’s why planting trees in Wolverley seemed like the obvious plan of action for us. Wolverley, like many places in the UK, has experienced a serious increase in flooding recently, having been flooded four times in the last decade. So we’re working with locals to plant trees - protecting the village from flooding and helping to tackle climate change too!

Photo: JR-P, cc