Rain splash soil erosion estimation in the presence of rock fragments

Abstract

Rain splash soil erosion in the presence of rock fragments and different initial conditions was tested in laboratory flume experiments under controlled conditions. The aim of the experiments was to ascertain whether cumulative soil erosion is proportional to the area of soil exposed to raindrop detachment under the condition of constant and uniform precipitation. The surface area exposed to rain splash erosion was adjusted by placing rock fragments onto the surface of identically prepared soil in laboratory flumes. The laboratory results showed that the eroded cumulative mass depended on the cumulative runoff, and that soil erosion was proportional to the soil surface area exposed to raindrops, in situations where an initially dry, ploughed and smoothed soil surface were ensured. The results showed that this relationship was controlled to a smaller extent by the soil's initial moisture content, bulk density and soil surface characteristics.When the initial conditions were more complex, soil erosion was proportional to the area exposed only at steady state. Then, sediment concentrations during the first part of the erosion event were instead more sensitive to the initial state of the soil surface, whereas at steady state it was observed that the concentrations of eroded sediments were controlled mainly by the effective rainfall and area exposed to raindrops. Previously published field data on rain splash soil erosion were analyzed to ascertain whether the same behavior was evident under field conditions. For this case it was found that rain splash erosion is in general not proportional to the area exposed. In contrast to the controlled laboratory experiments, the field experiments were characterized by non-uniform initial surface roughness, surface soil aging and heterogeneous rock fragment size and spatial distribution. However, the presented laboratory results showed clearly that, for soils with negligible surface roughness, erosion depends on (i) the area of soil 3 exposed to rainfall and (ii) the cumulative runoff, and that it is only slightly dependent on other soil variables.Keywords: Soil erosion experiment, Area exposed, Flume experiment, Cumulative discharge, Cumulative eroded mass, Soil initial conditions. IntroductionOver several decades, attention has been given to the effect of the soil surface characteristics (such as surface roughness, crop residues, organic mulches, vegetation cover and rock fragment coverage) on runoff generation, infiltration and soil erosion rates Poesen et al., 1999;Li, 2003;Gyssels et al., 2006;Smets et al., 2008;Knapen et al., 2009;Guo et al., 2010;Zavala et al., 2010). Numerous studies have pointed out the role played by surface rock fragments on erosion as well as on the hydrological response of soils (such as infiltration rate, surface ponding, runoff generation) (Adams, 1966;Poesen et al., 1990Poesen et al., , 1998Poesen et al., , 1999 Parsons, 1991, 1994;Bunte and Poesen, 1994;Ingelmo et al., 1994;Poesen and Lavee, 1994;Torri et al., 1994;van Wesemael et al., 19...

The impact of standard preparation practice on the runoff and soil erosion rates under laboratory conditions

“…Concentrations of runoff sediment after soil preparation confirmed that erosion depended directly on the sediment available on the soil surface that was in agreement with Ceballos et al (2002). The presence of pebbles and gravels on soil surface as well as inside soil profile has been considered as an affective factor against the kinetic energy of raindrops (Jomaa et al, 2012). The presence of stones at the soil surface does not always decrease soil erosion; on the contrary, if stones are embedded in crusted surfaces, they can increase runoff and thus soil erosion.…”

Linear scaling of precipitation-driven soil erosion in laboratory flumes

“…Similarly to Jomaa et al (2012a), results from experiments conducted using different precipitation rates, initial soil conditions and surface rock fragment coverage were analysed to test if the sediment concentrations (in the flume effluent) of the individual size classes decreased proportionally to the area exposed, as was found for the total suspended sediment 8 concentrations. The cumulative eroded mass per unit width was computed for each flume and experiment as the sum of multiplying the measured sediment concentration with its corresponding discharge rate per unit width.…”

“…Therefore, numerous studies have highlighted the importance of the use of simulated rainfall experiments to better understand soil erosion processes and to predict sediment delivery (e.g., Iserloh et al, 2013;Lassu et al, 2015;Martínez-Murillo et al, 2012). Jomaa et al (2012a) investigated the relationship between the temporal evolution of total eroded mass from a laboratory flume and the area exposed to raindrop detachment. In that study, the temporal soil erosion delivery from a rock fragment-protected flume (flume 2) was estimated by multiplying the time-varying eroded mass from the bare soil flume (flume 1) by the fraction of exposed soil to raindrops in flume 2.…”

Revegetation in abandoned quarries with landfill stabilized waste and gravels: water dynamics and plant growth – a case study

“…As a result, instead of directly topsoiling with LSW, we mixed it with gravels (2-3 cm in size) in different proportions, reusing rock fragments of quarry wastes as part of the growth substrate for plants, which is called LGM hereinafter. Not only do the embedded gravels constitute the primary fabric and thus enhance the stability of the mixture, the surface gravels can also reduce soil evaporation and conserve surface water (Yuan et al, 2009) and prevent fine earth from wind and splash erosion (Jomaa et al, 2012).…”