The speed of this urbanization picked up after World War II, and now many urban areas are growing at a record pace. In the table below, the left side shows changes in land and water use when urbanization occurs, and the right side shows the possible effect on the local water system. Begin building houses, some with sewers and some with septic tanks. Begin drilling wells. More storm runoff and erosion because there is less vegetation to slow water as it runs down hills.
More sediment is washed into streams.
Flooding can occur because water-drainage patterns are changed. Filling in of farm ponds. Building of roads. Diverting streams to supply water for people. Discharging of sewage into streams.