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.
- Science for Environment Policy: Grass and trees in urban areas help reduce flood risk (pdf, 220 KB)