Slope–Velocity–Equilibrium and evolution of surface roughness on a stony hillslope

Zhang

et al. 2018

Hydrological Processes

Water erosion on hillslopes is a worldwide environmental problem, which is a rainfall‐induced process, especially extreme rainfall. The great intensity of extreme rainfall strongly enhances the power of overland flow to detach soil and transport sediment. Plant litter is one of the most important constituents of ecosystems that often covers the soil surface and can be incorporated into topsoil. However, little attention has been paid to its effect on flow hydraulics owing to the veiled nature. This study aimed to examine the effects of incorporated litter on the hydraulic properties under extreme rainfall condition. To reach this goal, six litter rates of 0, 0.05, 0.10, 0.20, 0.35, and 0.50 kg m−2 and four litter types collected from deciduous trees, coniferous trees, shrubs, and herbs were incorporated into topsoil. Then, simulated rainfall experiments were performed on five slope gradients (5°, 10°, 15°, 20°, and 25°) with an extreme rainfall intensity of 80 mm h−1. The results showed that Froude number and flow velocity of the overland flow decreased, whereas flow resistance increased exponentially with litter incorporation rate. Litter type had an influence on flow hydraulics, which can mainly be attributed to the variations in surface coverage of the exposed litter and the litter morphology. Flow velocity and Darcy–Weisbach coefficient increased markedly with slope gradient. However, the variation of slope gradient did not modify the relationships between flow hydraulics and incorporated litter rate. The random roughness, resulting from heterogeneous erosion due to the uneven protection of surface exposed litter, increased linearly with litter incorporated rate. As rainfall proceeded, flow hydraulics varied with incorporated litter rate and slope gradient complicatedly due to the increases in flow rate and coverage of the exposed litter and the modification of soil surface roughness.

Section: Resultsmentioning

confidence: 97%

Hydraulics of overland flow influenced by litter incorporation under extreme rainfall

Zhang

et al. 2018

Hydrological Processes

“…Soils in semiarid areas that have been left bare after abandonment or land use change are one of the most important environmental factors driving soil erosion in arid and semiarid areas (Hueso‐González, Martínez‐Murillo, & Ruiz‐Sinoga, ; Kavian, Golshan, & Abdollahi, ; Nearing et al, ). Tillage and the overuse of herbicides causes a lack of vegetation cover that leaves soils uncovered and unprotected.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of vegetative buffer strips at reducing runoff, soil erosion, and nitrate transport during degraded hillslope restoration in northern Iran

et al. 2018

Soil and water conservation in natural and cultivated areas is a major concern for humankind. However, there are severe problems with degraded hillslopes due to bare soils in northern Iran, which are one of the most important factors driving land degradation processes. Subsequently, soil erosion, pollutant transport, and/or nutrient impoverishment are affecting large territories; therefore, rapid and inexpensive soil conservation measures need to be implemented. The use of vegetative buffer strips could be an effective strategy to reduce pollutant transport as well as soil erosion.Thus, this research aimed to investigate the possible efficiency of two different vegetative buffer strips composed of vetiver-grass (Chrysopogon zizanioides) and native turf-grass (Festuca arundinacea) at reducing runoff and soil losses as well as nitrate transport on a representative degraded hillslope with bare soils in Mazandaran, Iran.Twelve 10 m 2 experimental plots were tested over 1 year using a runoff simulator that produced overland flow that corresponded to the 25-and 100-year return period rainfall events. The plots with bare soils had the highest runoff volumes (30.5 and 55.4 L m −2 ), sediment concentrations (101.2 and 430.6 g L −1 ), and nitrate concentrations (10.4 and 37.6 mg L −1 ). Vetiver was the most useful tool to reduce runoff, soil loss, and nitrate concentration, with values of 13.4 and 28.6 L m −2 , 13.4 and 90.9 g L −1 , and 2.9 and 16.4 mg L −1 , respectively. Of the treatments investigated, vetiver provided the most rapid cover and was the most efficient at preventing soil erosion and nitrate transport directly after plantation.

European J Soil Science

“…Therefore, rock fragments from the local parent materials could be a good option to reduce soil losses, and improve soil physical properties (van Wesemael et al ., ), soil biology (Certini et al ., ), soil moisture (Jiménez et al ., ), soil porosity and productivity (Nyssen et al ., ) at a low cost. Rock fragments may increase infiltration when not embedded and reduce soil losses because they can act as a protective cover (Nearing et al ., ). Most of the current research has been carried out under laboratory conditions with disturbed soil (Poesen et al ., ; Poesen & Lavee, ) or on forest and rangeland soil (Cerdà, ); however, we do not know the effect of rock fragment cover and disturbance in a managed vineyard setting.…”

Section: Introductionmentioning

confidence: 97%

Role of rock fragment cover on runoff generation and sediment yield in tilled vineyards

Rodrigo‐Comino

García‐Díaz

Brevik

et al. 2017

SummaryThe soil in conventional Mediterranean vineyards is an active and non-sustainable source of sediment and water. Lack of vegetation cover, small soil organic matter content and intense ploughing result in large rates of erosion in a millennia-old tillage system. There is a need for soil conservation strategies that enable sustainability of wine and grape production; therefore, it is essential to measure the rates and to investigate the processes and factors of soil erosion. This study evaluated factors that can reduce soil losses in traditional Mediterranean vineyards. The investigation was carried out with 96 rainfall simulation experiments at the pedon scale (0.24 m 2 ) to measure soil detachment and runoff yield under low frequency-high magnitude rainfall events of 1 hour at 55 mm hour −1 . On average, runoff was 40.6% of the rainfall, and the rate of soil erosion (i.e. amount of soil lost) was 71.5 g m −2 . The key factor controlling erosion was the rock fragment cover. There was a clear decrease in soil losses with increased rock fragment cover on the soil surface, but an increase in surface runoff. The results of our study showed that rock fragments at the pedon scale reduced soil erosion in Mediterranean vineyards, but when a layer of embedded rock fragments developed, large rates of runoff were triggered. Highlights• We investigated soil erosion factors in Mediterranean vineyards.• Rainfall simulation at the pedon scale achieved accurate measurements.• Rock fragment cover reduces soil losses.• Embedded rock fragment cover will trigger large runoff rates.