FLOW AND SEDIMENT CONNECTIVITY IN SEMI-ARID LANDSCAPES IN SE SPAIN: PATTERNS AND CONTROLS

Much of the water and sediment fluxes in semi-arid catchments are found to be highly concentrated in localized pathways. Identifying the location of these pathways in the landscape is important for management and restoration. Measures can then be targeted so as to minimize the potential for erosion and sediment flux along these pathways. A method of repeat field mapping of flow and sediment pathways suitable for Mediterranean catchments is presented. Several small catchments in Carcavo basin, SE Spain, differing in topographic and land use characteristics, were monitored under several events. Morphometric properties of pathways were analysed and compared with rainfall characteristics. Number and length of pathways varied with rainfall characteristics and also antecedent conditions. In low rainfall events, runoff sources and main pathways were disconnected, but in a larger event, the network of pathways became fully connected. The pathway patterns showed that man-made lines such as terrace embankments and tracks have a major influence on sediment connectivity. Micro-topographic factors, soil moisture and the presence of vegetation are highly influential on pathways and the frequency of water and sediment fluxes. Runoff and erosion hotpots for the development of pathways were identified, which should be targeted for mitigation and restoration measures using vegetation. The relevance of local scale factors emphasizes the importance of repeat field observations to understand connectivity and pathways development in the landscape. Copyright (C) 2015 John Wiley & Sons, Ltd.