Soil cracking effects on hydrological and erosive processes: a study case in Mediterranean cultivated vertisols

Abstract

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.

A Spatiotemporal Multiscale Analysis of Runoff and Erosion in a Mediterranean Marly Catchment

“… September–November: Heavy rainfall on bare soil with open cracks induced very low runoff with very high sediment concentrations. The low runoff that occurred when topsoil cracks were present can be related to bypass flow, which enters the soil through open topsoil cracks (Inoubli et al, 2016). The high sediment concentration in surface runoff in autumn may be the result of soil shrinkage processes that occurred during the dry season and destroyed topsoil crusting and aggregation, which favored future soil particle detachment and export.…”

“…According to the FAO classification (2006), the soil types observed within the catchment are vertisols or assimilated (65%), regosols (25.5%), and eutric regosols (9.5%). Approximately two‐thirds of soils in Kamech are consequently very sensitive to cracking and exhibit numerous wide and deep open cracks during the entire dry summer period (Inoubli et al, 2016).…”

“…In addition, vegetation cover development for the different crops and the evolution of topsoil cracks were documented every 15 or 30 d on 25 fields in Kamech that were selected to represent the main crop and soil type associations. Intra‐annual evolution of vegetation cover was reported by Raclot and Albergel (2006) and intra‐annual evolution of cracks by Inoubli et al (2016). An intensive topographic monitoring of a representative permanent gully (included in P2+G) was also conducted in Kamech between 2002 and 2009 using a total station (El Khalili et al, 2013).…”

“…The highly dynamic shrink–swell processes of such soil types due to changing soil water storage conditions (Messing and Jarvis, 1993; Favre et al, 1997; Bagarello et al, 1999) generates soil cracks and extreme seasonal variations in soil infiltration rates. As a result, their hydro‐erosive response appears to be very complex at the micro, plot, and catchment scales (Gómez et al, 2014; Inoubli et al, 2016). Therefore, studying the impact of cracking soils on runoff and erosion at different temporal and spatial scales also represents a specific and interesting challenge.…”

Determining Shrinkage Cracks Based on the Small-Strain Shear Modulus–Suction Relationship

“…Shrinkage cracks, within a short period of time, can cause the clay barrier system to malfunction through the formation of preferential flow paths in the barrier layers [8]. The presence of cracks on topsoil has different effects on the runoff and total erosion [9], and also the movement of fertilizers and pesticides to the root zone is impacted by the presence of these cracks [10]. Shrinkage cracks thus have led to a wide range of problems in diverse fields, and research to analyze their effects are vital.…”