Effects of surface rock fragment characteristics on interrill runoff and erosion of a silty loam soil

Abstract

The role played by rock fragments in water erosion has received much attention in recent years. Knowledge of the effects of rock fragment characteristics on interrill erosion is incomplete. Hence, in order to investigate these effects on a small scale, a simulation experiment was conducted in Bragan~a, Northeast Portugal. The experimental setup consisted of 48 bottom perforated rectangular metal boxes (612 cm2), placed at a 10% slope, filled with 3.5 cm of a sieved silty loam soil over 2 cm of sand, covered by simulated rock fragments and maintained at near saturation. Twelve treatments, four replicates each, were exposed to 240 mm natural rainfall, comprising selected combinations of rock fragments size (small, medium--gravel range, and large--stone range), shape (rectangular and circular), position (surface, half-embedded and embedded) and cover percentage (17, 30 and 66%), and bare soil. Infiltration depth, runoff depth, washed and splashed sediment were repeatedly measured in appropriate collection devices. For bare soil, total wash and total splash were equivalent to 42.2 g m -2 and 70.6 g m -2, respectively. Infiltration and runoff represented 52% and 13% of total rainfall, respectively. Wash has a negative exponential relationship with rock fragment cover (RC). The regression coefficient varies negatively with cumulative precipitation, decreasing significantly after a surface seal is formed (at about 80 mm cumulative precipitation). The relationship between splash and RC, linear and negative, varies with time, too. Correlation with RC is positive for infiltration depth and negative for runoff depth, both reflecting the seal development with time. The effects of rock fragments size, position and form were tested for 30% RC. Size has a positive effect on runoff depth, wash and splash, and a negative effect on infiltration depth. The effect of rock fragment size on infiltration, runoff and erosion is more pronounced than that of position. The effect of shape was less significant than that of size and position.

Effects of land use on annual runoff and soil loss in Europe and the Mediterranean

“…This is also illustrated by Engels (personal communication 2009) who notes that soil loss from an old undisturbed vineyard in the Moselle region, western Germany, is considerably lower (0.5 Mg.ha -1 .yr -1 ) than that from an adjacent vineyard where vines were removed and roots destroyed (4.4 Mg.ha -1 .yr -1 ). Nevertheless, no clear trends in annual SL between 8 and 17 years after vineyard establishment were found for vineyards in the Douro region, northern Portugal (de Figueiredo, personal communication 2010;de Figueiredo and Gonçalves Ferreira, 1993;de Figueiredo and Poesen, 1998). Brenot et al (2006) measured soil loss by vine stock unearthing (i.e.…”

Effects of rock fragment cover on hydrological response and soil loss from Regosols in a semi-humid environment in South-West China

“…When rock fragments rest on top of the soil surface, they on the one hand can reduce the kinetic energy of raindrops and inhibit surface soil sealing, and part of the rockflow (i.e. runoff generated by the rock surface) and part of the Hortonian overland flow generated in the sealed bare soil area between rock fragments, can be absorbed by the unsealed soil surface below rock fragments (de Figueiredo and Poesen, 1998). On the other hand, surface soil roughness is increased by the presence of rock fragments, which can block overland flow and increase infiltration time and pressure potential.…”

“…Parameters that have been reported to be important for explaining the degree of runoff or soil loss from soils containing rock fragments include the position (Poesen et al, 1990), size , geometry (Koon et al, 1970), and percentage cover (Mandal et al, 2005) of rock fragments and the structure of fine earth (Poesen and Ingelmo-Sanchez, 1992). De Figueiredo and Poesen (1998) suggest that the percentage of the rock fragment cover is the most important factor. Positive relationships have been observed between rock fragment sizes, infiltration rates, overland flow yield, and sediment.…”

A field investigation into the effects of progressive rainfall-induced soil seal and crust development on runoff and erosion rates: The impact of surface cover

“…9). Existing work on the influence of stone lags on runoff and sediment movement suggests that the positioning of the individual stones is quite important (Poesen et al, 1994;de Figueiredo and Poesen, 1998). On Summerford bajada, the stones are partially embedded in the soil and crusts and seals form around them.…”