A2.18 Water use, water quality and flood risk are likely to be affected where land use is changed, development or infrastructure is promoted or certain technological change is facilitated. For example, transport schemes may lead to social costs where polluted water runs off from new roads into local watercourses, a housing development may place pressure on local water supplies and new types of power station may increase freshwater abstraction to the detriment of local natural assets. Water or flooding impacts should be considered and valued as part of options appraisal.