Sediment concentration in interrill flow: interactions between soil surface conditions, vegetation and rainfall

Abstract

A database composed of 673 natural rainfall events with sediment concentration measurements at the field or plot scale was analysed. Measurements were conducted on similar soil type (loess soils prone to sealing phenomenon) to apprehend the variability and complexity involved in interrill erosion processes attributable to soil surface conditions. The effects of the dominant controlling factors are not described by means of equations; rather, we established a classification of potential sediment concentration domain according to combination of the dominant parameters. Thereby, significant differences and evolution trends of mean sediment concentration between the different parameter categories are identified. Further, when parameter influences interact, it allows us to discern the relative effects of factors according to their respective degree of expression. It was shown that crop cover had a major influence on mean sediment concentration, particularly when soil surface roughness is low and when maximum 6-min intensity of rainfall events exceeds 10 mm h 1 : mean sediment concentration decreases from 8Ð93 g l 1 for 0-20 per cent of coverage to 0Ð97 g l 1 for 21-60 per cent of coverage. The established classification also indicates that the increase of the maximum 6-min intensity of the rainfall factor leads to a linear increase of mean sediment concentration for crop cover over 21 per cent (e.g. from 2Ð96 g l 1 to 14Ð44 g l 1 for the 1-5 cm roughness class) and to an exponential increase for low crop cover (e.g. from 3Ð92 g l 1 to 58Ð76 g l 1 for the 1-5 cm roughness class). The implication of this work may bring perspective for erosion prediction modelling and give references for the development of interrill erosion equation.

Operational performance of current synthetic aperture radar sensors in mapping soil surface characteristics in agricultural environments: application to hydrological and erosion modelling

“…Microscale investigations, such as plot studies, have shown how patterns of SSC have a very strong influence on soil hydraulic properties, particle detachment, infiltration patterns, connectivity of runoff, distribution of flow velocities, and therefore the initiation of rilling (Loch, 1994;Dimanche and Hoogmoed, 2002;Leonard et al, 2006). Very simple SSC indicators based on vegetation cover, crusting and surface roughness appear to be the best indicators to explain the variability of the rill erosion rate between small catchment areas (Auzet et al, 1993) and are efficient for runoff and rill erosion modelling whether at this scale (Ludwig et al, 1995;Cerdan et al, 2002bCerdan et al, , 2002c or at a regional scale (Le Bissonnais et al, 2002Bissonnais et al, , 2005. Soil surface characterization now emerges, in addition to measurements of other base variables, as a major and efficient step towards a better spatial understanding of processes and more accurate soil erosion forecasting.…”

“…classes of increasing roughness height) or derived coefficients such as friction factors (Nearing et al, 1989;Foster, 1990;De Roo et al, 1996, Cerdan et al, 2002b2002c). For example, numerous soil erosion models use the Manning's roughness coefficient, and because of the difficulty of gathering spatially distributed input data, they draw simple empirical assumptions between a given land cover and a Manning's roughness coefficient value.…”

Modelling interrill erosion in small cultivated catchments

“…The calculation of potential sediment concentration at the field scale is based on the classification established by Cerdan et al (2002a) presented in Table I. It has been elaborated after the analysis of a database composed of 673 natural rainfall events with sediment concentration measurements at the field or plot scale collected under a variety of different situations in terms of weather conditions, soil surface properties, vegetation cover and agricultural practices.…”

“…These experimental references have highlighted significant differences and evolution trends of mean sediment concentration in interrill flow between different defined categories of soil surface conditions, vegetation and rainfall characteristics. Thus a classification of sediment concentration in interrill flow that accounts for parameter interactions has been elaborated (Cerdan et al, 2002a). The objective of this paper is to incorporate these results in the elaboration of the interrill erosion module of the STREAM model.…”

SCALES: a large‐scale assessment model of soil erosion hazard in Basse‐Normandie (northern‐western France)

“…Furthermore, erosion appears within the scope of an agricultural space organized very different. The type of erosion previously quoted refers to the northern-western cultivated lands in which agricultural patterns are simplifi ed and lead to a high connectivity and rapid runoff concentration (Souchère et al, 1998;Blanchard et al, 1999;Cerdan et al, 2002). In BasseNormandie, agricultural areas are partitioned because of (1) a dense network of vegetable hedges and soil embankments and (2) a high interpenetration of grassland and cultivated parcels (Brunet, 2004).…”