Rainfall-runoff-erosion relationships study for different land uses, in a sub-urban area

Abstract

Rainfall-runoff-erosion relationships are poorly understood. The complexity introduced in hydrological properties and processes by land use changes as a result of urban sprawl further increases the unpredictability. To study the impact of urbanization, we selected a sub-urban catchment in Central Portugal, the “Ribeira dos Covoes”, where urban sprawl and land use changes are leading to changes in hydrological processes. This study surveys the hydrological response of different signifi cant land uses within the catchment, by performing rainfall simulations experiments at small plot scale (0.25 m2). The results show distinct overland fl ow responses for different land uses. The agriculture areas (including tilled and abandoned) showed no overland fl ow generation, after a rainfall of 43 mm h-1. In forest, clear felled areas and in build-up areas, overland fl ow ranged from 21 % to 83 % of total rainfall. However, parameters such as water repellence, soil moisture content, vegetation and litter surface soil cover were important to explain overland fl ow generation. The amount of sediments moved during the experiments was associated with overland fl ow generation. Values reached 172 g m-2 in hillslopes disturbed by construction sites. The high organic content of the sediments collected (more than 90 % in some cases), pinpoint the importance of nutrients relocation within different land uses.