Maintain or restore hydrology

Changes in climate may increase runoff during heavy storm events in some areas. Impermeable surfaces are more common in the urban setting and direct water into water bodies through storm sewers. Stormwater thus bypasses vegetation and other natural features that could slow water flow and reduce pollution. Vegetation and associated ecosystem features can filter, intercept, and absorb stormwater, reducing runoff and improving the quality of water reaching streams and lakes. Water is intercepted by the tree canopy and held by the root systems of herbaceous and woody plants and associated soil organic material. In highly developed areas where large areas of vegetation are not feasible, engineered features can also be used to increase permeability and help redistribute water.

The changing climate may alter the complex interactions among climate, vegetation, and landforms, resulting in changes in hydrology, soil quality, and nutrient cycling. Urban areas often involve further complications because of the greater likelihood that human activities have already significantly altered ecosystem functioning and will continue to do so. Urban conditions are often characterized by difficult growing conditions, including impermeable surfaces, air and water pollution, frequent human interaction, and small soil volumes. Existing guidelines and best management practices for forest management describe actions that can be used to reduce or reverse impacts to soil and water. Many of these actions are also likely to be beneficial in the context of adaptation, although additional effort may be required to maintain ecosystem function in urban areas.