Trees, Our Allies Against Flooding

Trees do much more than simply beautify our landscapes! In town and country, they act as air purifiers, absorbing CO2, releasing oxygen and capturing atmospheric pollutants. They also play an important role in combating climate change by storing carbon in their wood, thereby helping to regulate atmospheric CO2. They also lower ambient temperatures by providing shade and limiting heat islands, like natural air conditioners. In terms of biodiversity, each tree offers refuge to birds, insects and small mammals essential to the balance of ecosystems. Their presence also benefits our mental and physical health: trees reduce stress, improve mood and encourage activity.

But did you know that they also play a role in flood prevention: they absorb rainwater, slowing its flow and helping to limit the saturation of drainage systems.

True Umbrellas

Trees are natural flood barriers. By intercepting precipitation with their canopies, they slow the flow of water to the ground, a bit like a big green umbrella that allows rain to take its time soaking into the ground rather than rushing into rivers and urban sewers. Research shows that tree canopies can capture between 19% and 21% of precipitation.

By delaying the arrival of water in drainage systems, trees help reduce the peak volumes that often trigger flash floods. This gradual absorption attenuates the intense runoff that can overwhelm watercourses and overload storm drainage systems. What’s more, some of the water intercepted by branches and leaves evaporates before even reaching the ground, further reducing the amount of water to be managed during periods of heavy rain. Trees are a more efficient water management system than many infrastructures!

Soil Stabilization and Erosion Reduction

The deep roots of trees act as solid anchors, stabilizing the soil and limiting erosion, which would otherwise send sediment directly into watercourses. This root network effectively traps soil particles and other pollutant debris before they reach rivers, enabling them to maintain their capacity to flow unobstructed. In urban environments, trees planted along riverbanks become veritable living filters, intercepting sediments and pollutants before they reach the watercourses. This plant integration helps to keep rivers flowing smoothly and prevent sudden overflows, which are often responsible for flooding. What’s more, by protecting the topsoil, trees preserve not only the quality of the soil, but also the surrounding ecosystems, making them healthier and more resistant to long-term climatic variations.

Heavy Drinkers

Tree roots help rainwater to penetrate gently and deeply into the soil. As they spread, they loosen the soil around them, reducing compaction and facilitating water absorption. Thanks to this underground network, water doesn’t run off the surface, but quietly seeps in, recharging the water table. And with a few well-thought-out tricks – such as reduced slopes and well-adapted soils – this absorption can really be optimized. In places such as South-East Asia, forests have even been found to regulate river flow by allowing better infiltration. The ability of trees to absorb water is essential for managing flood risks and adapting to the effects of climate change on water availability.

Like a Rain Barrel

Once the water has been absorbed, the soil surrounding the tree roots keeps it cool, ready to reach the water table if need be, and the trees themselves become little natural reservoirs. What’s more, they release a good deal of moisture into the air through evapotranspiration, a real breath of fresh air for the water cycle, especially in the city between showers. Under their cover, the soil remains moist, helping to limit runoff during heavy rains. Forested landscapes, on the other hand, act as giant sponges, absorbing, retaining and slowly releasing water into watercourses. The end result is a more constant flow, less frequent flooding and a beautiful harmony between rain and stream – with no need for anyone to intervene!

The Right Tree in the Right Place

As with all plants, trees are not suitable for all locations, and the choice of species and their location are crucial to maximizing flood protection and ensuring long-term plantation survival. Choose your trees carefully, taking into account light conditions, soil type and moisture content, and other environmental factors. Trees are a long-term investment: take the time to get to know them well before inviting them into your garden. Be as careful as in love, because a well-chosen tree will enrich your living space for years to come!