Changing rate of urban creep and urban expansion over time and its impact upon the hydrologic response of a catchment

Abstract

Most previous quantitative research conducted on urban creep and urban expansion has focused on small areas, short time periods, case studies with fairly uniform housing stock and demographic makeup, and the characterisation of urban creep and expansion exclusively in terms of impervious area changes without quantification of the consequential hydrological impact, i.e., increase in surface runoff volume and peak flows in a catchment. This study, using satellite imagery, catchment characteristics data, geographic information system and hydrologic modelling, presents, for the first time, a long-term analysis of urban creep and expansion. The case study is the Ouseburn catchment in Newcastle upon Tyne, a wide-ranging catchment made up of rural, suburban and urban areas, over a period of seven decades. The rate of increase of impervious surfaces is found not to be constant in time; the significant impact of this variation on the catchment's hydrologic response is quantified. This has overall caused a substantial flow volume increase in the Ouseburn over the study period, e.g. 48% for a 1 in 5 years rainfall event. The conclusions obtained are likely representative of many large towns and cities across the United Kingdom and the methodology presented can be easily replicated in other study areas. HIGHLIGHTS First long-term study into the changing rate of Urban Creep and Urban Expansion.; Results facilitate the prediction of future levels of imperviousness in urban areas.; Increased imperviousness has resulted in faster catchment hydrological response.; Greater levels of imperviousness have also produced larger peak flows.; Established links between socio-demographics and varying rates of urban creep.;

Keywords

• hydrological impact
• hydrological modelling
• urban change
• urban creep
• urban expansion