Structural and functional control of surface-patch to hillslope runoff and sediment connectivity in Mediterranean dry reclaimed slope systems

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.

Influence of seasonal vegetation dynamics on hydrological connectivity in tropical drylands

“…These seasonal dry biomes include zones such as dry forests in Central and South America (Banda et al, 2016;Gerard et al, 2020;Lima et al, 2018), dry forests in the Horn of Africa region (Van Passel et al, 2020), and sub-Saharan tree savannas (Räsänen et al, 2020). These biomes exhibit continuous ground cover, mainly during wet season, contrasting with subtropical/ Mediterranean drylands, with interchanges between vegetation patches and bare areas (Bergkamp, 1998;Dickie & Parsons, 2012;Hoffman et al, 2013;Moreno-De-Las-Heras et al, 2020;Okin et al, 2015;Puigdefábregas, 2005;Puttock et al, 2013;Urgeghe & Bautista, 2015).…”

Interannual evolution of hydrosedimentary connectivity induced by forest cover change in a snow‐dominated mountainous catchment

“…While the topography‐based impedance factors generally lead to static connectivity, it has been shown that connectivity can be highly dynamic over time, especially when considering land use/forest cover change (Llena et al, 2019; Moreno‐de‐las‐Heras et al, 2020; Ortíz‐Rodríguez, Muñoz‐Robles, & Borselli, 2019; Poeppl, Keesstra, & Maroulis, 2017). Thus, to best evaluate the effect of forest cover change on connectivity, we implemented a highly dynamic impedance factor in IC computation that was based on HR rates.…”

“…When land use and/or vegetation cover are used to determine the impedance driving IC, it is clear that the dynamic state of connectivity is a critical issue. Indeed, it is widely recognized that connectivity generally evolves over time (Cossart et al, 2018), due both to topography (Calsamiglia et al, 2018; Llena et al, 2019) and particularly to variations in land use/vegetation cover (Brierley, Fryirs, & Jain, 2006; Coulthard & Van De Wiel, 2017; Czuba & Foufoula‐Georgiou, 2015; Moreno‐de‐las‐Heras et al, 2020; Wohl, 2017; Wohl et al, 2019), yet few studies have incorporated land use changes into IC computation to assess its impact on the evolution of hydrosedimentary connectivity through time (Table 1). To evaluate the impact of land degradation on the evolution of hydrosedimentary connectivity, these studies produced diachronic land use maps and transformed them into diachronic impedance maps using Manning's n , C‐factor, or satellite remote‐sensed indices with the aim of eventually including them in IC computations.…”

Event controls on intermittent streamflow in a temperate climate

“…Although extensive research on overland flow and subsurface stormflow generation at the hillslope and reach scale, as well as baseflow contributions to perennial streams, has been conducted, there are still few studies on the dynamic controls of flow occurrence in ephemeral and intermittent reaches (James and Roulet, 2009;Zimmer and McGlynn, 2017). Studies of intermittent streams can be roughly categorised into the following four scales: (1) continental-scale studies based on discharge measurements (Reynolds et al, 2015;Eng et al, 2016;Trancoso et al, 2016;Jaeger et al, 2019), (2) (nested) catchment-scale studies based on wet/dry mapping of the stream network (Godsey and Kirchner, 2014;Sando and Blasch, 2015;Shaw, 2016;Goodrich et al, 2018;Jensen et al, 2017Jensen et al, , 2018, (3) single-site or hillslope-scale studies based on conventional discharge measurements (Sidle et al, 1995;Ries et al, 2017;Moreno-de-las-Heras et al, 2020), and (4) (multi)catchment-scale studies that are based on continuous measurements of streamflow presence and absence with low-cost sensors (i.e. temperature, electric conductivity, or flow sensors and time-lapse cameras) at multiple locations along the stream to monitor the intermittent stream network (Jaeger and Olden, 2012;Zimmermann et al, 2014;Zimmer and McGlynn, 2017;Jensen et al, 2019;Kaplan et al, 2020a).…”