John McCarthy, Shillelagh, Co Wicklow

DEAR SIR: There are two principal reasons for fresh water flooding. The first is rainfall; the second is the way in which land and rivers respond to this rainfall.

If the uplands, where most of our rain falls, are kept bare, rainfall flashes off them. Tree cover greatly increases the rate at which rain is absorbed by the soil.

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The result is that instead of rushing off the hills and into the nearest river, it is released more slowly and the flood peaks are likely to be lower. Studies have found infiltration rates to be up to 60 times higher within woodland shelter belts compared to grazed pasture. Afforestation can reduce flood peaks by 50%.

Tree planting, both in the hills and along watercourses, could significantly reduce flooding, soil erosion and water pollution.