The study of the consistent transformation of hydrological regimes that results from urban development. These changes have been attributed to the construction of impervious surfaces and the compaction of pervious surfaces, which promote rapid surface run-off from rainfall, and the efficient drainage of surface run-off through storm sewers to the river network. The percentage urban land cover/ percentage impervious cover/percentage connected impervious cover within a catchment provide simple but very effective predictors of changes in streamflow characteristics resulting from urban development (A. O. Akan and R. Houghtalen 2003). See Gurnell et al. (2007) Geog. Compass 1, 5 for an excellent review of the topic.