Trees can act as a natural flood defence. They have roots that reach deep into the soil, loosening it and allowing water to drain down more easily. A hillside covered in thick vegetation tends to release water more slowly than a bare hill. The compacted soil of farmland can also make the problem worse by reducing the ground’s ability to hold water.This is especially important upstream. Planting woodlands at a stream’s upper reaches could help delay the water from reaching the main river. Trees can also end up providing small dams, although this needs to be managed with care.Blanket bogs also play a key role in soaking up rainfall upstream. The peaty soil of a bog can be up to 90% water. Sphagnum mosses growing there can also hold water like a sponge. But many blanket bogs have been drained and their peat cut out which can increase the risk of flooding downstream.
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