Search results for "sediment transport"

Modelling soil carbon fate under erosion process in vineyard

2017

Soil erosion processes in vineyards beyond water runoff and sediment transport have a strong effect on soil organic carbon loss (SOC) and redistribution along the slope. The variation of SOC across the landscape determines a difference in soil fertility and vine productivity. The aim of this research was to study erosion of a Mediterranean vineyard, develop an approach to estimate the SOC loss, correlate the vines vigor with sediment and carbon erosion. The study was carried out in a Sicilian (Italy) vineyard, planted in 2011. Along the slope, six pedons were studied by digging 6 pits up to 60cm depth. Soil was sampled in each pedon every 10cm and SOC was analyzed. Soil erosion, detachment …

Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)

2017

International audience; The authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay…

Non-uniform Sediment Transport Estimation in Non-equilibrium Situations: Case Studies

2014

Abstract Quantitative estimate of sediment transport in alluvial channels is one of the most important task in river engineering. Even today, numerical models of sediment transport processes are confronted with some difficulties, often of conceptual nature. One of these difficulties is the simulation of non-uniform sediment transport in non-equilibrium situations, which requires the characterization of the ability of the alluvial system to immediately overcome the variations of the sediment boundary conditions. In this work a 1-D numerical model, which includes a new expression of the so-called “adaptation coefficient”, has been applied to test its capability to simulate the transient bed p…

Nonuniform sediment transport estimation in non-equlibrium situations: study cases

2014

Experimental Observation Of Turbulent Structures In A Straight Flume

2010

Experimental and theoretical studies of the structure of turbulence in open-channel flows have shown that the dynamics of the wall layer turbulence is dominated by the formation and growth of turbulent structures which evolve periodically as part of the so-called bursting phenomena. In the present paper experimental results obtained in a straight flume for different roughness conditions of the channel walls are described. The occurrence of turbulent events is verified by applying the conditioned quadrant analysis. The information about the spatial and temporal scales of the events is obtained through the space-time correlations of the conditioned data.

EXPERIMENTAL ANALYSIS OF RELATION BETWEEN COHERENT TURBULENT STRUCTURES AND BED-FORMS FORMATION

2008

The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measures of flow velocity components have been carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) has been verified through the conditioned quadrant analysis. The quantitative information about the spatial and temporal evolution of turbulent events has been obtained through the space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence the bed-forms formation, the spatial scale of turbu…

Environmental control on granular clinoforms of ancient carbonate shelves

2006

The purpose of this paper is to document the influence of depositional environments on shallow-water, low-relief clinoforms from the description of five ancient carbonate platforms: the Neoproterozoic (Namibia), Middle Jurassic (France), Lower Cretaceous (France), Upper Cretaceous (Oman) and Miocene (Turkey). These examples have been investigated on the basis of field observations. The clinoforms are described with reference to geometric and compositional attributes: declivity, shape, height, sedimentary structures, sediment fabric and components. The results show great variability in stratal geometry, declivity and facies distribution: (1) depositional profiles vary from exponential, to si…

Morphological characterization of calanchi (badland) hillslope connectivity

2017

Calanchi, a type of Italian badlands created by a combination of water erosion processes and local geomorphological and tectonic controls, is a striking example of long-term landscape evolution. In small temporal/spatial scales, the calanchi exhibit many of the geomorphic processes and landforms that may be observed in fluvial landscapes, hence they may be considered as micro-basins where geomorphic dynamics and landscape features can be related. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms. In order to detect the morphological characteristics controlling the landscape connectivity of calanchi basins,…

Variable scale effects on hillslope soil erosion during rainfall-runoff processes

2021

Abstract The variation of soil erosion across scales remains a controversial issue. A theoretical framework, coupling the normalized Green-Ampt equation for infiltration, 1D kinematic wave model for overland flow, and WEPP erosion modeling approaches for soil erosion, was used to explain and quantify the direct effect of scale on the soil erosion process. The results show that the relation between interrill erosion and slope length accords with a power-law decreasing trend, while the relation of rill erosion versus slope length shows a power-law increasing trend. Moreover, the power-law scaling of interrill erosion becomes more prominent with an increase of rainfall duration and intensity b…

Sediment transport mechanisms and selective removal of soil particles under unsteady-state conditions in a sheet erosion system

2022

Abstract Selective removal of particles and nutrients by water erosion is a key factor in soil erosion studies. Most agricultural soils are located on gentle slopes where fertility is high; however, until now, the main attention on sediment transport mechanisms was paid to high-slope gradients, where soil erosion is intense, but soils are less productive. Despite the importance of sediment size distribution (SSD) and transport mechanisms under unsteady-state conditions, few studies have been done on this issue. Higher sediment concentrations in the early stages of the runoff indicate the need to deal with unsteady-state conditions. To address this issue, sheet erosion experiments were done …