Shrink–swell soils, such as those in a Mediterranean climate regime, can cause changes in terms of hydrological and erosive responses because of the changing soil water storage conditions. Only a limited number of long‐term studies have focused on the impacts on both hydrological and erosive responses and their interactions in an agricultural environment. In this context, this study aims to document the dynamics of cracks, runoff and soil erosion within a small Mediterranean cultivated catchment and to quantify the influence of crack processes on the water and sediment supplied to a reservoir located at the catchment outlet using water and sediment measurements at a cultivated field outlet as baseline. Detailed monitoring of the presence of topsoil cracks was conducted within the Kamech catchment (ORE OMERE, Tunisia), and runoff and suspended sediment loads were continuously measured over a long period of time (2005–2012) at the outlets of a field (1.32 ha) and a catchment (263 ha). Analysis of the data showed that topsoil cracks were open approximately half of the year and that the rainfall regime and water table level conditions locally control the seasonal cracking dynamics. Topsoil cracks appeared to seriously affect the generation of runoff and sediment concentrations and, consequently, sediment yields, with similar dynamics observed at the field and catchment outlets. A similar time lag in the seasonality between water and sediment delivery was observed at these two scales: although the runoff rates were globally low during the presence of topsoil cracks, most sediment transport occurred during this period associated with very high sediment concentrations. This study underlines the importance of a good prediction of runoff during the presence of cracks for reservoir siltation considerations. In this context, the prediction of cracking effects on runoff and soil erosion is a key factor for the development of effective soil and water management strategies and downstream reservoir preservation. Copyright © 2016 John Wiley & Sons, Ltd.

An intensive monitoring investigation was conducted within the Kamech catchment (Cape Bon, Tunisia) to document the effect of scale on the hydrological and erosive responses in a Mediterranean climate regime with cracking soils. An evaluation of the individual contribution of topsoil and gully processes to total sediment delivery at different spatial scales was also conducted. Continuous runoff and erosion measurements during a 7-yr period at four nested gauging stations were examined in a plot (P1; 1.32 ha), a plot + gully (P2+G; 1.37 ha), a micro-catchment (MC; 15.2 ha), and the entire catchment (C; 263 ha). Data analysis showed a high interannual variability and contribution of only a few events; three major events generated approximately 20% of the total runoff and at least 50% of the total erosion at all of the monitoring stations. The results also highlight the strong seasonal dynamics of both water and sediment delivery, with a time lag observed between runoff and sediment responses. The presence of open cracks in autumn was identified as a main factor explaining this time lag. A constant monthly and annual specific runoff response was observed among the stations, and a simple linear model combining a single rate of topsoil (17 t ha −1 yr −1 ) and gully (80 t ha −1 yr −1 ) erosion (weighted by their contribution area) successfully predicted the differences observed in the mean annual erosion rates among the stations. Finally, this work showed the predominance of topsoil erosion processes in a Mediterranean catchment that is characterized by cracking soils and very high hydro-sedimentary connectivity.Currently, soil erosion is a recognized environmental problem (Kefi and Yoshino, 2010). Scientists have devoted considerable efforts to understanding and predicting erosion occurrence. They have intensively studied soil erosion processes throughout the last decades using monitoring systems at the plot scale and at larger scales (Boix-Fayos et al., 2006;Cerdan et al., 2010;Vanmaercke et al., 2012). If water erosion factors are now well known (Wischmeier and Smith, 1978), the complex hierarchy of erosion processes across a wide range of spatial and temporal scales still needs to be studied (Wei et al., 2012;Cerdà et al., 2013). The study of the scale effect on soil erosion processes requires different methods to understand the redistribution of sediments along the source-transport-sink continuum (Lane et al., 1997). Research on soil erosion has established that factors controlling the movement of water and sediment vary according to a range of spatial scales, and the connections are complex (Cammeraat, 2002;de Vente and Poesen, 2005). Furthermore, the evolution of the system and the subsequent hydrological and erosion response are highly dependent on the interactions and dominant processes at the studied scales (Cammeraat, 2002;Boix-Fayos et al., 2007). Indeed, different factors and processes controlling runoff and erosion may act at distinct scales in different ways. Therefore, we need to understand the fact th...