Vegetation in urban areas helps to reduce flood risk

Planting grass and trees in place of asphalt could help reduce rainfall runoff (and the potential consequent sewage system flooding) in urban areas, a new report has found. To prevent stormwater systems from overflowing during periods of prolonged heavy rainfall, scientists tested two types of vegetated area – grass and trees – compared to paved area, to see how much the runoff could be reduced.

They found that, compared to paved areas, the tree-planted area (planted with small field maples producing a ~35% canopy cover) reduced the average rainfall runoff by 58% in winter and 62% in summer. Grassy areas reduced runoff to less than 1% of the total rainfall; provided the soil under the grass is not overly compacted, grassy areas in urban places could make a  significant contribution to reducing flooding.