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Large rills with catchment areas measuring tens to hundreds of square metres pose serious soil erosion problems to South China, after deforestation has exposed the deeply weathered granitic slopes to the impacts of tropical rainstorms. Runoff and sediment discharges of rills respond rapidly to rainfall, but compared with bare rills, vegetated rills show considerably lower amounts of flow and sediment...
Although several scientists have recently studied overland flow detachment, the methodology of measurement has not yet been properly discussed. This study compares several different methods. A flume was constructed to measure soil detachment. Remoulded soils were tested in order to minimize the effects of sediment load and deposition on the soil sample surface by way of a suitable methodology....
Concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover (Rc) on sediment yield for an initially wet and an initially air-dry loamy topsoil. The experimental results indicate that Rc reduces concentrated flow erosion rates (E) in an exponential way (i.e., E=e -b ...
This study deals with the characteristics which make a rainstorm an event that can produce intense erosion and even trigger the formation of a badlands site. In order to keep the presentation closely linked to a real situation, a rainstorm which took place on an experimental farm equipped for soil erosion studies was selected. The effects of the erosive rainstorm, which fell on dry antecedent moisture...
Indicators were obtained to measure and predict rill erosion and mass wasting in biancana and calanchi-like badland areas. Rainfall simulation experiments were used to find a relationship between soil moisture change and sediment concentration behaviour. This relationship appeared to be able to show, in its role as indicator, differences between materials affected by various degrees of rill erosion...
Soil erosion is commonly measured as the quantity of sediment leaving a plot or watershed. The techniques for measuring soil erosion patterns and sediment redistribution within plots or watersheds by direct monitoring are very limited. The objective of this study was to develop a direct and non-intrusive tracer method to study the sources, patterns and rates of erosion and deposition of sediments...
The understanding of soil erosion processes and the development of accurate erosion prediction models require understanding of detachment, deposition, and sediment transport in rills. The objectives of this study were to determine whether sediment transport capacity is a unique value for given soil, flow rate, and slope, and to determine if equilibrium sediment concentration in the rill obtained by...
This study was carried out in Pang Prarachatan village, which is located in Chiang Rai province of northern Thailand. The farmers in this village construct bench terraces to reduce soil erosion and increase plant productivity. However, severe soil erosion occurs frequently on the bare bench terraces. This study investigates the impact of bench terracing on soil erosion. The use of weeds and plant...
To properly assess soil erosion in agricultural areas, it is necessary to determine precisely the volume of ephemeral gullies and rills in the field by using direct measurement procedures. However, little information is available on the accuracy of the different methods used. The main purpose of this paper is to provide information for a suitable assessment of rill and ephemeral gully erosion with...
Fire in sagebrush rangelands significantly alters canopy cover, ground cover, and soil properties which influence runoff and erosion processes. Runoff can be generated more quickly and in larger volume following fire resulting in increased risk of severe erosion and downstream flooding. The Water Erosion Prediction Project (WEPP) model was developed to predict erosion on cropland, forest, and rangeland...
Rill hydraulics (and hence, flow detachment) are modified by the presence of incorporated vegetation residue. Typically, water flow in the rill is retarded due to the extra shear stress generated by the residue. The main objective of this study was to develop an approach to predict soil detachment by rill flow in the presence of freshly incorporated vegetation residue that is compatible with our current...
The strongly incised mountain landscape of northern Thailand has changed dramatically during the last few decades due to increased population pressure, agricultural commercialization, limitation to use old fallows and reforestation of upper catchments. The traditional shifting cultivation with fallow periods of 7 years and longer was gradually replaced by 1 to 4 year fallow periods. As a result, in...
Cover crops are a very effective erosion control and environmental conservation technique. When cover crops freeze at the beginning of the winter period, the above-ground biomass becomes less effective in protecting the soil from water erosion, but roots can still play an important role in improving soil strength. However, information on root properties of common cover crops growing in temperate climates...
Despite many efforts over the last decades to understand rill erosion processes, they remain unclear. This paper presents the results of rill experiments accomplished in Andalusia in September 2008 using a novel experimental set up. 72L of water are introduced with an intensity of 9Lmin −1 into a rill. Rill cross sections, slope values, flow velocities and sediment concentrations were measured...
This paper tackles two main questions by linking observations, determination of hydraulic parameters and measurement of sediment transport with the formulae used in soil erosion models. First, do constant shear stress values in different rills with constant soil parameters result in the same soil detachment values? Secondly, deterministic soil erosion models make the assumption that there is a relationship...
The biancana badlands, a typical element of the southern Tuscany landscape, were in expansion for centuries, until bulldozers began erasing them for land reclamation purposes. Over the last 10–15years some of the scattered remnants of biancanas have been placed under protection in order to preserve their biodiversity and their particular cultural and geomorphological landscapes. Rural abandonment...
The impact of slope aspect on hydrological rainfall and on the magnitude of rill erosion has rarely been studied. The dominant wind direction in Belgium and northern France is the southwest, which brings large amounts of rain with it. We investigated whether this leads to greater rates of rill erosion on the southwestern slopes, due to the greater amount of hydrological precipitation on these slopes...
To reduce the rate of soil erosion and improve the environment, the Chinese government launched the “Grain for Green” project in 1999, and afforestation with fish-scale pits (FSPs) is one of the main measures of this project in the steppe zone on the Loess Plateau. In this study, tree survival and growth, vegetation recovery and differences in soil erosion between afforestation with FSP slopes (AFS)...
Soil erosion from row sideslopes can result in contour failure and reduce the soil conservation capacity of contour ridges. Understanding soil erosion processes on row sideslopes and their effects will improve our understanding of soil erosion in contour ridge systems. This knowledge will provide guidance for improving the use of contour ridges. In this study, 32 rainfall simulation experiments were...
Numerous soil erosion models compute concentrated flow hydraulics based on the Manning–Strickler equation (v=k St R 2/3 I 1/2 ) even though the range of the application on rill flow is unclear. Unconfined rill morphologies generate local friction effects and consequently spatially variable rill roughness which is in conflict with the assumptions of (sectional) uniform channel...
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