Plants such as trees and grasses help hold the soil in place. Soil erosion is a serious problem in urban areas due to the loss of vegetation from construction, neglect, and/or overuse of surfaces in public recreation and gathering places. In addition, surfaces that are impervious to water infiltration, such as pavement, concentrate flows of water and runoff across exposed soil. Unfortunately, soil erosion results in water pollution problems through deposition of sediment in urban waterways. Sedimentation is a major reason many urban areas have enhanced stormwater management programs.