Abstract
Abstract. Connectivity has emerged as a useful concept for exploring the movement of water and sediments between landscape locations and across spatial scales. In this study, we examine the structural and functional controls of surface-patch to hillslope runoff and sediment connectivity in three Mediterranean dry reclaimed mining slope systems that have different long-term development levels of vegetation and rill networks. Structural connectivity was assessed using flow path analysis of coupled vegetation distribution and surface topography, providing field indicators of the extent to which surface patches that facilitate runoff and sediment production are physically linked to one another in the studied hillslopes. Functional connectivity was calculated using the ratio of patch-scale to hillslope-scale observations of runoff and sediment yield for 21 monitored hydrologically active rainfall events. The impact of the dynamic interactions between rainfall conditions and structural connectivity on functional connectivity were further analysed using general linear models with a backward model structure selection approach. Functional runoff connectivity during precipitation events was found to be dynamically controlled by antecedent precipitation conditions and rainfall intensity and strongly modulated by the structural connectivity of the slopes. On slopes without rills, both runoff and sediments for all events were largely redistributed within the analysed hillslopes, resulting in low functional connectivity. Sediment connectivity increased with rainfall intensity, particularly in the presence of rill networks where active incision under high-intensity storm conditions led to large non-linear increases in sediment yield from the surface-patch to the hillslope scales. Overall, our results demonstrate the usefulness of applying structural- and functional-connectivity metrics for practical applications and for assessing the complex links and controlling factors that regulate the transference of both surface water and sediments across different landscape scales.
Highlights
IntroductionMoreno-de-las-Heras et al.: Structural and functional control of runoff and sediment connectivity interact at a variety of spatial scales (from the surface-patch to the plot, hillslope and catchment scales), resulting in intricate responses of runoff and sediment yield (Puigdefabregas et al, 1999; Calvo-Cases et al, 2003; Cammeraat, 2004; Yair and Raz-Yassif, 2004; Boix-Fayos et al, 2006; Morenode-las-Heras et al, 2010; Mayor et al, 2011; Gallart et al, 2013; Marchamalo et al, 2016)
Surface processes in Mediterranean landscapes are affected by multiple factors thatPublished by Copernicus Publications on behalf of the European Geosciences Union.Medicago sativa (Ms)
Sink areas for Slope 3 were broadly distributed in the form of densely vegetated shrub clumps (Gs and Santolina chamaecyparissus (Sch) surface-patch types) within the central and lower sections of the slope system (Fig. 3c), largely hindering the connectivity between the source areas distributed at the top of the slope and the outlet of the system
Summary
Moreno-de-las-Heras et al.: Structural and functional control of runoff and sediment connectivity interact at a variety of spatial scales (from the surface-patch to the plot, hillslope and catchment scales), resulting in intricate responses of runoff and sediment yield (Puigdefabregas et al, 1999; Calvo-Cases et al, 2003; Cammeraat, 2004; Yair and Raz-Yassif, 2004; Boix-Fayos et al, 2006; Morenode-las-Heras et al, 2010; Mayor et al, 2011; Gallart et al, 2013; Marchamalo et al, 2016) In these complex systems, connectivity has emerged as a useful concept for studying the movement and transference of surface water and water-borne materials (e.g. sediments, nutrients and seeds) between landscape locations or scales (Bracken and Croke, 2007; Wainwright et al, 2011; Bracken et al, 2013; Reaney et al, 2014; Keesstra et al, 2018; Saco et al, 2020). Functional connectivity is a function of the detachment, entrainment, deposition and remobilization of sediments across scales (Wainwright et al, 2011; Bracken et al, 2013; Turnbull and Wainwright, 2019)
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