Why forests are critical to regulate flood risks
Forests play a critical role in reducing flood risk by promoting evaporation, improving soil structure, decreasing soil erosion, and exerting a drag on floodwaters, which delays flood flows. Also, trees absorb and store water during dry periods, reducing the risk of drought and ensuring a more consistent supply of water for agriculture and human consumption. Trees can also help regulate temperature, reducing the risk of heatwaves and other extreme weather events exacerbated by climate change.
Regional climate, geology, soil type, and soil condition all influence tree water use and the effectiveness of tree planting in reducing flood risk. For example, planting in the wetter and windier uplands of the UK will maximize the contribution of storm-day, canopy interception loss to reducing flood flows, while woodland creation in the warmer and drier lowlands will potentially contribute more below-ground floodwater storage due to greater soil drying and higher soil moisture deficits. However, this can exacerbate low flows in dry periods and pose an issue for water supplies and the wider freshwater environment, so it's important to consider downstream waters and wetlands that are sensitive to a reduction in water quantity.