Erosion Deposition Model Research Articles

Simulation of sediment yield from watershed by physiographic soil erosion–deposition model

Runoff and sediment are two of the critical factors for watershed management. This study developed a physiographic soil erosion-deposition model (PSED) by application of GIS to a physiographic rainfall-runoff model. The PSED model was evaluated for Chin-Shui river watershed based upon rainfall events occurred from 1990 to 1996. Runoff discharges and the concentration of suspended sediment hydrographs were estimated first, followed by sediment yield. PSED was found to be able to estimate the sediment yield within reasonable range as compared to the observed data.

Modelling eutrophication in mesotidal and macrotidal estuaries. The role of intertidal seaweeds

The role of intertidal seaweeds in the primary production of mesotidal and macrotidal estuaries has been examined by means of a model, applied to the Tagus Estuary (Portugal). Special attention was paid to the description of the underwater light climate in intertidal areas, and to the importance of the formation of tidal pools. Two approaches were compared for the simulation of suspended particulate matter (SPM) in the pool areas, using three algal species. The use of an erosion–deposition approach to simulate the distribution of SPM in tidal pools gives an increase in net primary productivity per unit area of between 130 and 1300%, when compared to the more conventional approach where the suspended matter in the overlying water in intertidal areas is considered identical to that in the channels. The upscaled erosion–deposition model was applied to tidal pool areas and combined with the more conventional model for other intertidal areas. Results show that annual carbon fixation by intertidal seaweeds in the estuary exceeds 13,500 t C yr −1, and accounts for 21% of the total carbon fixed by all primary producers. The corresponding nitrogen removal by seaweeds corresponds to the annual nutrient loading of a population of 490,000 inhabitants.

Two-stage erosion and deposition in a continental margin setting: an 40 Ar/ 39 Ar laserprobe study of offshore detrital white micas in the Norwegian Sea

Detrital white micas from a restricted region of the Norwegian Sea have been analysed by the 40 Ar/ 39 Ar laserprobe. Examining the ages of individual white mica grains from offshore Triassic, Jurassic and Cretaceous sandstones reveals a narrow range of detrital white mica ages (369–424 Ma). Moreover, there is an inverse relationship between sediment age and detrital white mica age, with the Triassic sands containing a larger proportion of younger white micas, and the Cretaceous sands containing the oldest white micas. In addition, residence times of the detritus, which is the age of the sediment subtracted from the age of the detrital white mica, range from c. 150 to c. 300 Ma (for the Triassic and Cretaceous sands respectively). The inverse age relationships combined with the large residence times for these stratigraphic levels can best be explained by an erosion-deposition model involving at least two stages. Taking into account previous provenance studies in the Lofoten region of the Norwegian Sea, these new data suggest that detritus shed initially from the exhuming Caledonian nappes of NW Norway in late Silurian-early Devonian times was deposited in intramontane basins that were themselves, subsequently unroofed and re-eroded from Permo-Triassic times. This caused the recycling of the Caledonian detritus from the Devono-Carboniferous basins and led to the inverted detrital age distribution ovserved in the Triassic-Cretaceous sediments examined in this study. While sedimentary recycling is not a surprising feature for Mesozoic basins in the North and Norwegian Seas, this study documents a previously untapped method, 40 Ar/ 39 Ar laserprobe provenance studies, by which to identify its effect and extent.

Numerical simulation of drifting snow: erosion and deposition models

Earlier works on numerical modelling are analysed. Anderson and Haff (1991) proposed a model using the “splash” function which was defined for cohesionless sand. The Uematsu and others (1989, 1991) and Liston and others (1993,1994) approaches are based on fluid-mechanics conservation laws where the snow is transported and diffused by the air flow. These models consider the saltation layer as a boundary condition.For the flow, and for the suspension, we adopt the same model as that of Uematsu and Liston. For mass exchange between the flow and snow surface, we have developed an erosion–deposition model where mass exchange is defined in relation to flow turbulence, threshold-friction velocity and snow concentration. Our snow-erosion model was calibrated using Takeuchi's(1980) field measurements. The deposition model was tested by comparing numerical results with wind-tunnel ones, for sawdust-accumulation windward and leeward of a solid snow fence with a bottom gap. The numerical results obtained are close to the experimental results. The main results of the various sensitivity experiments are: the leeward accumulation is very sensitive to the ratio (u*/u*t) (it appears for (u*/u*t) close to 1 and disappears for (u*/u*t) > 1.2), the global accumulation produced by the fence increases as (u*/u*t) decreases and the back reaction of particles on turbulence extends slightly the windward accumulation.

Numerical simulation of drifting snow: erosion and deposition models

Earlier works on numerical modelling are analysed. Anderson and Haff (1991) proposed a model using the “splash” function which was defined for cohesionless sand. The Uematsu and others (1989, 1991) and Liston and others (1993,1994) approaches are based on fluid-mechanics conservation laws where the snow is transported and diffused by the air flow. These models consider the saltation layer as a boundary condition.For the flow, and for the suspension, we adopt the same model as that of Uematsu and Liston. For mass exchange between the flow and snow surface, we have developed an erosion–deposition model where mass exchange is defined in relation to flow turbulence, threshold-friction velocity and snow concentration. Our snow-erosion model was calibrated using Takeuchi's(1980) field measurements. The deposition model was tested by comparing numerical results with wind-tunnel ones, for sawdust-accumulation windward and leeward of a solid snow fence with a bottom gap. The numerical results obtained are close to the experimental results. The main results of the various sensitivity experiments are: the leeward accumulation is very sensitive to the ratio (u*/u*t) (it appears for (u*/u*t) close to 1 and disappears for (u*/u*t) > 1.2), the global accumulation produced by the fence increases as (u*/u*t) decreases and the back reaction of particles on turbulence extends slightly the windward accumulation.

GIS-based simulation of erosion and deposition patterns in an agricultural landscape: a comparison of model results with soil map information

This paper presents a relatively simple, two-dimensional hillslope erosion-deposition model: the model differs from most geomorphological models in that it does not assume that erosion by surface wash is always transport-limited. As a first test, the model is applied to an agricultural catchment in Central Belgium. Here, patterns of past erosion and deposition can be deduced from information contained in the Belgian Soil Map so that a qualitative validation of the model results is possible. The results indicate that a simple model formulation allows to reproduce the basic pattern of erosion and deposition as it is observed in the landscape. This confirms the major influence of topography on erosion and deposition patterns in such landscapes and indicates that in some cases a simple model formulation may well be sufficient to allow adequate modelling of landscape evolution.

Erosion, deposition and size distributions of sand

A mathematical–physical model for erosion and deposition of sand is formulated and related to the logarithmic hyperbolic distributional form of mass–size distributions. The location-scale invariant parameters χ and ξ of the hyperbolic distribution express, respectively, the skewness and the kurtosis of that distribution, and the triangular domain of variation of these two parameters is referred to as the hyperbolic shape triangle. The erosion–deposition model implies that erosion will tend to move the ( χ , ξ)-position of a given sediment to the right-hand part of the shape triangle and that deposition will move the ( χ , ξ)-position towards the left part of the triangle, along specified curves. This is confirmed by sediments from a variety of natural environments. An empirically determined curve bisecting the shape triangle is found to separate the samples from predominantly depositional environments as compared with the samples from predominantly erosional environments. The hyperbolic shape triangle is also found to discriminate well between samples of different but closely related origins.

Modeling the effects of mining and erosion on biomass production

A biomass productivity model and a soil loss model were used to simulate effects of mining and erosion on the productivity potential of a 600-ha site. Biomass productivity, expressed as a relative productivity index pi ( 0 ⩽ pi ⩽ 1 ), was computed as a product of a root distribution function and limiting soil property levels derived from literature. Distribution of soil loss or deposition was estimated using a recently developed erosion-deposition model. Effects of two scenarios are compared. In the first, the site is assumed to have been surface mined for coal and the effects on productivity are examined if existing soil is replaced with a minesoil. In the second, erosion-deposition model is used to predict changes in productivity after a severe storm. Under the assumptions of this study, biomass productivity appears more likely to decline because of mining than because of erosion.

QUANTITATIVE EVALUATION OF SEDIMENT DELIVERY RATIOS1

SummaryAbility to adequately estimate sediment yield is an important step in dealing effectively with soil erosion problems. Predictions of sediment yield made using the Universal Soil Loss Equation (USLE) with different forms of sediment delivery ratio (SDR) are compared with those made by Modified USLE (MUSLE) and a fundamentally derived Erosion‐Deposition Model (EDM). The USLE and USLE with SDR are poor predictors of sediment yield for individual storms compared to the MUSLE and EDM. Although MUSLE gave better results than USLE it showed somewhat more scatter of data points than the recently developed EDM.