ABSTRACT
Land take by urban development is a major hydrologic threat: it entails soil sealing and compaction, impervious surfaces may collect pollutants that are periodically washed off, and artificial drainage generally transfers runoff away much more quickly than in natural watersheds. This chapter discusses the impacts of soil sealing and land take from urban development in terms of water quality, water availability and floods, and summarizes options for the mitigation of impacts on floods and water availability. These affect the water cycle, hence ecology, as well as water availability and flood hazards in catchments. The effects of soil sealing have been identified as a significant threat to water bodies and should be appropriately addressed first of all by limiting impervious surfaces in a catchment and by avoiding their direct drainage to streams.
