Erosion Deposition Model Research Articles

NUMERICAL MODELLING OF SNOW DEPOSITS AND SNOW TRANSPORT ON LONG-SPAN ROOFS FOR STEADY AND UNSTEADY FLOW

This paper presents the methodologies for numerical modelling of snow deposits and snow transport on long-span roofs for steady and unsteady flow. The calculation of snow loads on long-span roofs is a complex problem, solving which often involves deviating from the building code recommendations. Experiments in wind tunnels, although widely used, do not allow reproducing the full-scale effects of all snow accumulation processes. At the same time, the continuous improvement of mathematical models, numerical methods, software and computer technologies makes the development and implementation of numerical modelling technologies in real construction practice and regulatory documents inevitable. In this paper it is shown that the use of the well-known erosion-deposition model, supported by field observations and experimental data, allows reproducing reasonably accurate snow distributions on long-span roofs. The importance of the “synthesis” between physical and mathematical modelling and the application of the building codes is emphasized, as only the joint use of approaches can comprehensively describe modelling of snow accumulation and snow transport and provide better solutions to a wider range of related problems.

Formation and development of coral reefs in the South China Sea

Coral reefs are unique geologic bodies that are formed by biological activity in tropical and subtropical oceans and coastal areas. When and how these reefs came into being and reached their present scales in the ocean remain controversial. Based on strontium, carbon and oxygen isotopes and mineralogical, micropaleontological and elemental analyses of the coral Meiji Reef in the Nansha Islands, South China Sea, we reconstructed the formation and evolutionary history of the island. The results show that the coral reef developed on top of a volcanic basement under the combined influence of diverse factors, especially regional tectonic movement and long-term climatic change. The evolution of the reef was divided into eight stages based on these factors. Extensive exposure was frequently found on the island, and an almost 1000-m thick coral reef eroded simultaneously. The entire development process of coral reefs on the island may be explained by a phased erosion deposition model, which was also found to be suitable for studying the development of coral reefs in the Xisha Islands. We suggest that many coral reefs in the tropics may not flourish continuously over long periods of time, and sedimentary hiatuses normally occur in the layers of coral reefs.

DriftScalarDyFoam: An OpenFOAM-Based Multistage Solver for Drifting Snow and Its Distribution Around Buildings

There is a complex coupling relationship between the airflow and snow cover. In a period of hours or even days, the airflow will cause the redistribution of snow, and the redistribution of snow will cause the airflow to change. This study develops a dynamic mesh technology applied in snow drifting simulation through a real-time dynamic mesh update to depict the snow surface evolution process under long-period snow drifting, and a solver application named driftScalarDyFoam based on OpenFOAM is implemented. This solver divides the long-period snow drifting process into several stages, in each of which a snow transport equation is applied to predict the spatial distribution of snow, and finally, the snow surface evolves according to the erosion–deposition model. This method that we have proposed has been validated for several measured cases, including snow distribution on a flat roof and snow distribution around a building.

A mechanical erosion model for two-phase mass flows

Erosion, entrainment and deposition are complex and dominant, but yet poorly understood, mechanical processes in geophysical mass flows. Here, we propose a novel and process-based two-phase erosion-deposition model capable of adequately describing these complex phenomena commonly observed in landslides, avalanches, debris flows and bedload transports. The model is based on the jump in the momentum flux including changes of material and flow properties along the flow-bed interface and enhances an existing general two-phase mass flow model (“Pudasaini S.P., 2012, A general two-phase debris flow model, Journal of Geophysical Research, 117, F03010, doi:10.1029/2011JF002186”). A two-phase variably saturated erodible basal morphology is introduced which allows for the evolution of erosion-deposition-depths, incorporating the inherent physical process including momentum and rheological changes of the flowing mixture. By rigorous derivation, we show that appropriate incorporation of the mass and momentum productions or losses in conservative model formulation is essential for the physically correct and mathematically consistent description of erosion-entrainment-deposition processes. We show that mechanically deposition is the reversed process of erosion. We derive mechanically consistent closures for coefficients emerging in the erosion-rate models. We prove that effectively reduced friction in erosion is equivalent to the momentum production. With this, we solve the long standing dilemma of mass mobility, and show that erosion enhances the mass flow mobility. The novel enhanced real two-phase model reveals some major aspects of the mechanics associated with erosion, entrainment and deposition. The model appropriately captures the emergence and propagation of complex frontal surge dynamics associated with the frontal-drag with erosion.

Estimating soil organic carbon redistribution in three major river basins of China based on erosion processes

Soil erosion by water affects soil organic carbon (SOC) migration and distribution, which are important processes for defining ecosystem carbon sources and sinks. Little has been done to quantify soil carbon erosion in the three major basins in China, the Yangtze River, Yellow River and Pearl River Basins, which contain the most eroded areas. This research attempts to quantify the lateral movement of SOC based on spatial and temporal patterns of water erosion rates derived from an empirical Unit Stream Power Erosion Deposition Model (USPED) model. The water erosion rates simulated by the USPED model agreed reasonably with observations (R2 = 0.43, P < 0.01). We showed that regional water erosion ranged within 23.3–50 Mg ha–1 year–1 during 1992–2013, inducing the lateral redistribution of SOC caused by erosion in the range of 0.027–0.049 Mg C ha–1 year–1, and that caused by deposition of 0.0079–0.015 Mg C ha–1 year–1, in the three basins. The total eroded SOC was 0.006, 0.002 and 0.001 Pg year–1 in the Yangtze River, Yellow River and Pearl River Basins respectively. The net eroded SOC in the three basins was ~0.0075 Pg C year–1. Overall, the annual average redistributed SOC rate caused by erosion was greater than that caused by deposition, and the SOC loss in the Yangtze River Basin was greatest among the three basins. Our study suggests that considering both processes of erosion and deposition – as well as effects of topography, rainfall, land use types and their interactions – on these processes are important to understand SOC redistribution caused by water erosion.

Application of physiographic soil erosion–deposition model in estimating sediment flushing efficiency of empty storage

In this study, we developed a physiographic soil erosion–deposition model to simulate sediment yield from a watershed into Agongdian reservoir and sediment flushing to estimate the efficiency of empty flushing. The model was verified using data related to Typhoons Morakot and Fanapi. Thereafter, we calculated the sediment flushing efficiency of empty storage under the conditions of 1- and 2-day storms with seven return periods. The simulated results revealed that the amount of sediment yield from Joushui River watershed was approximately 70% on average, whereas that from Wanglai River watershed was approximately 30%. These results are consistent with those of a government research report, which suggested that the sediment yield figures from Joushui and Wanglai River watersheds were 72 and 28%, respectively. Furthermore, the efficiency of empty flushing was more than 55% when using the shaft spillway pipe, suggesting that the model can be applied to estimate sediment yield and flushing efficiency.

Advection and dispersion of bed load tracers

Abstract. We use the erosion–deposition model introduced by Charru et al. (2004) to numerically simulate the evolution of a plume of bed load tracers entrained by a steady flow. In this model, the propagation of the plume results from the stochastic exchange of particles between the bed and the bed load layer. We find a transition between two asymptotic regimes. The tracers, initially at rest, are gradually set into motion by the flow. During this entrainment regime, the plume is strongly skewed in the direction of propagation and continuously accelerates while spreading nonlinearly. With time, the skewness of the plume eventually reaches a maximum value before decreasing. This marks the transition to an advection–diffusion regime in which the plume becomes increasingly symmetrical, spreads linearly, and advances at constant velocity. We analytically derive the expressions of the position, the variance, and the skewness of the plume and investigate their asymptotic regimes. Our model assumes steady state. In the field, however, bed load transport is intermittent. We show that the asymptotic regimes become insensitive to this intermittency when expressed in terms of the distance traveled by the plume. If this finding applies to the field, it might provide an estimate for the average bed load transport rate.

Erosion and deposition processes in surface granular flows.

We report on experiments aiming at characterizing erosion and deposition processes on a tilted granular bed. We investigate the existence of the neutral angle, that is, the critical angle at which erosion exactly balances accretion after the passage of a granular avalanche of a finite mass. Experiments show in particular that the neutral angle depends on both avalanche mass and shape but is rather insensitive to the bed length. This result strongly suggests that the effective friction between the static and mobile granular phases cannot be taken as an intrinsic property that is only material dependent but should be considered a flow-dependent property. Interestingly, for a given avalanche mass, the net erosion rate increases linearly with the angular deviation from the neutral angle. We also compare our data with the predictions of the erosion-deposition model introduced by Bouchaud, Cates, Ravi Prakash, and Edwards (BCRE) [J. Phys. I 4, 1283 (1994)JPGCE81155-430410.1051/jp1:1994195]. We show that the predictions drawn from the modified version of the BCRE model proposed by Boutreux and de Gennes, in which the local erosion rate between the static and mobile phases is independent of the flow thickness, are in remarkable agreement with the experimental results.

Sediment Accumulation in Prairie Wetlands under a Changing Climate: the Relative Roles of Landscape and Precipitation

Sediment accumulation threatens the viability and hydrologic functioning of many naturally formed depressional wetlands across the interior regions of North America. These wetlands provide many ecosystem services and vital habitats for diverse plant and animal communities. Climate change may further impact sediment accumulation rates in the context of current land use patterns. We estimated sediment accretion in wetlands within a region renowned for its large populations of breeding waterfowl and migrant shorebirds and examined the relative roles of precipitation and land use context in the sedimentation process. We modeled rates of sediment accumulation from 1971 through 2100 using the Revised Universal Soil Loss Equation (RUSLE) with a sediment delivery ratio and the Unit Stream Power Erosion Deposition model (USPED). These models predicted that by 2100, 21–33 % of wetlands filled completely with sediment and 27–46 % filled by half with sediments; estimates are consistent with measured sediment accumulation rates in the region reported by empirical studies. Sediment accumulation rates were strongly influenced by size of the catchment, greater coverage of tilled landscape within the catchment, and steeper slopes. Conservation efforts that incorporate the relative risk of infilling of wetlands with sediments, thus emphasizing areas of high topographic relief and large watersheds, may benefit wetland-dependent biota.

An integrated assessment of soil erosion dynamics with special emphasis on gully erosion in the Mazayjan basin, southwestern Iran

Soil erosion by water is a significant problem in arid and semi-arid areas of large parts of Iran. Water erosion is one of the most effective phenomena that leads to decreasing soil productivity and pollution of water resources; especially, in the Mazayjan watershed in the southwest of Fars Province gully erosion contributes to the sediment dynamics in a significant way. Consequently, the intention of this research is to identify the different types of soil erosion processes acting in the area and to assess the process dynamics in an integrative way. Therefore, we applied GIS and satellite image analysis techniques to derive input information for the numeric models. For sheet and rill erosion the Unit Stream Power-based Erosion Deposition Model (USPED) was utilized. The spatial distribution of gully erosion was assessed using a statistical approach, which used three variables (stream power index, slope, and flow accumulation) to predict the spatial distribution of gullies in the study area. The eroded gully volumes were estimated for a 7-year period by fieldwork and Google Earth high-resolution images. Finally the gully retreat rates were integrated into the USPED model. The results show that the integration of the SPI approach to quantify gully erosion with the USPED model is a suitable method to qualitatively and quantitatively assess water erosion processes. The application of GIS and stochastic model approaches to spatialize the USPED model input yields valuable results for the prediction of soil erosion in the Mazayjan catchment. The results of this research help to develop an appropriate management of soil and water resources in the southwestern parts of Iran.

Spatial distribution of soil erosion and suspended sediment transport rate for Chou-Shui river basin

In this study, a Physiographic Soil Erosion–Deposition Model (PSED) is applied for better management of a watershed. The PSED model can effectively evaluate the key parameters of watershed management: surface runoff discharge, suspended sediment transport rate, quantity of soil erosion, and spatial distribution of soil erosion and deposition. A basin usually contains multiple watersheds. These watersheds may have complex topography and heterogeneous physiographic properties. The PSED model, containing a physiographic rainfall-runoff model and a basin scale erosion–deposition model, can simulate the physical mechanism of the entire erosion process based on a detailed calculation of bed-load transportation, surface soil entrainment, and the deposition mechanism. With the assistance of Geographic Information Systems (GIS), the PSED model can handle and analyze extremely large hydrologic and physiographic datasets and simulate the physical erosion process without the need for simplification. We verified the PSED model using three typhoon events and 40 rainfall events. The application of PSED to Chou-Shui River basin shows that the PSED model can accurately estimate discharge hydrographs, suspended sediment transport rates, and sediment yield. Additionally, we obtained reasonable quantities of soil erosion as well as the spatial distribution of soil erosion and deposition. The results show that the PSED model is capable of calculating spatially distributed soil erosion and suspended sediment transport rates for a basin with multiple watersheds even if these watersheds have complex topography and heterogeneous physiographic properties.

A Comparative Analysis of Lajeunesse Model with other Used Bed Load Models - Effects on River Morphological Changes

Among the phenomena that greatly influence the river morphology is the sediment transport, especially the bed load mode causing a significant changes in the river morphology. Indeed, the choice of a model or a methodology that can better quantify sediment transport, remains always poorly understood. In this context, a new approach to studying the morphological evolution of rivers is proposed by Charru in 2004, it is based on a model for the erosion and deposition of the particles under laminar flow. In 2006, Charru proposes an extension of this model to turbulent flow. In more advanced research, Lajeunesse in 2010, realizes an experimental study to support the erosion deposition model of Charru, and proposes a new formula to calculate the bed load transport rate. The current research focuses on the effects of bed load transport on the morphological changes in rivers. In the first part, a comparative analysis of empirical laws of bed load transport with experimental data was conducted, in order to test and validate the new bed load model proposed by Lajeunesse, then to check the grain size effect on the sediment transport capacity. In the second part, we are interested in the study of the morphological evolution in rivers. It was performed through numerical modeling using TELEMAC 2D coupled with SISYPHE. The aim is to understand and analyze the morphological changes in the channel bottom. The analysis of the results presented in this paper showed that through the calculated score, most formulas give satisfactory results. In particular at the grain scale, the new bed load transport relation of Lajeunesse, provides an excellent fit to the experimental data. Finally, we were interested in the study of the morphological changes in the channel bottom, it appers clear that the bed load transport has large impacts on river morphology.

Tracer dispersion in bedload transport

Abstract. Bedload particles entrained by rivers tends to disperse as they move downstream. In this paper, we use the erosion-deposition model of Charru et al. (2004) to describe the velocity and the spreading of a plume of tracer particles. We restrict our analysis to steady-state transport above a flat bed of uniform sediment. The transport of tracer particles is then controlled by downstream advection and particle exchange with the immobile bed. After a transitional regime dominated by initial conditions, the evolution of a plume of markers tends asymptotically towards classical advection-diffusion: its average position grows linearly with time, whereas it spreads like the square root of time.

Study on One Dimensional Mathematical Model for Unsteady Flow Sediment and Water Quality in Channel with a Sluice

Based on existing mathematical model for one-dimensional unsteady flow and non-uniform water-sediment, the inside boundary condition of sluice has been introduced to establish a mathematical model which is suitable for sediment and water quality in nontidal river channel with sluice, in combination with empirical model of local erosion-deposition and one-dimensional mathematical model for water quality. It can be used to simulate motion of water flow, sediment and pollutant under different operational modes of sluice in tidal reaches. In addition, a mathematical model calculation software for water-sediment and water quality has been developed on this basis after sluice has been built, which is also being used to study the influence of different application solution of sluice in Yongding New River on the motion of sediment and pollutant, so as to provide a basis for the selection of sluice operational modes.

Study on One Dimensional Mathematical Model for Unsteady Flow Sediment and Water Quality in Channel with a Sluice

Based on existing mathematical model for one-dimensional unsteady flow and non-uniform water-sediment, the inside boundary condition of sluice has been introduced to establish a mathematical model which is suitable for sediment and water quality in nontidal river channel with sluice, in combination with empirical model of local erosion-deposition and one-dimensional mathematical model for water quality. It can be used to simulate motion of water flow, sediment and pollutant under different operational modes of sluice in tidal reaches. In addition, a mathematical model calculation software for water-sediment and water quality has been developed on this basis after sluice has been built, which is also being used to study the influence of different application solution of sluice in Yongding New River on the motion of sediment and pollutant, so as to provide a basis for the selection of sluice operational modes.

Estimating sediment deposition volume in a reservoir using the physiographic soil erosion-deposition model

A traditional way to estimate the amount of sediment deposition in a reservoir is simply based on the variation in the elevation measurements made at different times. In the present study, a physiographic soil erosion-deposition (PSED) model is applied to Tseng-Wen reservoir watershed to compute the discharge and sediment concentration into the reservoir, and the deposition volume. The PSED model is verified using three storm events and then compared to the historic data recorded at the hydrological stations in the reservoir watershed, which shows close agreement between the simulated and recorded values of the flow discharge into the reservoir and the corresponding sediment yield. The numerical simulation was also conducted for all rainfall events from 1996 to 2001 to estimate the annual sediment deposition volume in the reservoir. Similarly, the simulated result was compared to that obtained from the cross-section elevation measurement. It is found that some measured data points had large uncertainty or were questionable. On the contrary, the model results and the measured data that renders the model credible. Therefore, regardless of the estimation for the flow discharge into the reservoir induced by a single rainfall event, the sediment yield, or the sediment deposition, the PSED model has successfully demonstrated its ability.

철재형 이안제 설계기법 연구 III. 투과성 철재형 이안제 후면에서의 해저면 변화

In order to solve various problems associated with gravity-type breakwaters, the permeable breakwaters are recently taken into account as an alternative tool to control wave heights to an acceptable level. In particular, they are favored from the point of view of coastal environment, since they do not in general partition the natural sea. In this study, therefore, we present a morphodynamic model applied to scattering wave fields. The numerical solutions are compared with experimental data on wave profiles and morphological change rates under a surface-piercing breakwater system. Our numerical study involves several modules: 1) nonlinear wave dynamics analyzed by a plane-wave approximation, 2) suspended sediment transport combined with sediment erosion-deposition model, and 3) concurrent morphological changes. Scattering waves are solved by using a plane wave method without inclusion of evanescent modes.

Assessing the effects of geomorphological processes on archaeological densities: a GIS case study on Zakynthos Island, Greece

While geomorphological processes are considered key factors in the distribution of archaeological surface finds, few studies have attempted to quantify the relationship between artefact dispersal and erosional/depositional patterns. This paper compares Unit Stream Power Erosion Deposition model (USPED) and Revised Universal Soil Loss Equation (RUSLE) and integrates the results in the archaeological finds’ density map of Zakynthos Archaeological Project. The study area (Palaiokastro), with artefacts dated from middle Paleolithic to medieval times, includes a steep terrain with a surrounding plain area, where the downslope erosion has considerably modified the distribution of archaeological remains. Through this study, it is possible to identify relationships between high artefact densities and stable/non-eroded surfaces, and on the other hand, low densities and eroded surfaces. However, the results indicate a degree of spatial variability, which modifies the predicted relationship. The consideration of the effects of these temporal and spatial patterns is crucial for developing effective sampling methods and accurately interpreting the archaeological record.

Selection of the ripple length on a granular bed sheared by a liquid flow

The stability of a granular bed sheared by a liquid flow is investigated using an erosion-deposition model for the moving grains. Extending to arbitrary wave number a previous long wave analysis [F. Charru and E. J. Hinch, J. Fluid Mech. 550, 111 (2006)], this study shows that short waves are stabilized by a crest-erosion mechanism that is absent when the local particle flux is assumed to be in equilibrium with the local bed shear stress. The cutoff length associated with this mechanism scales on a deposition length of the particles. This characteristic length is similar, although of a different physical nature, to the inertial length involved in relaxation models of dune dynamics under the wind. Two stabilizing mechanisms cooperate for the most amplified wave number: the new crest-erosion mechanism and the gravity force parallel to the local slope of the inclined bed. The predictions of this model are compared to observations, showing better agreement than previous stability analyses, which strongly underpredict the observed lengths.

Modeled carbon sequestration variation in a linked erosion–deposition system

Unraveling the consequences of hydrologic transport on carbon (C) storage will help identify feedbacks between land management alternatives, climate change, and soil-vegetation-atmospheric-transfers (SVATs) of C. There is a need for theoretically driven models of erosion and deposition that includes transport induced mineralization to better understand the controls on SVATs of C. Here we present a model developed using a systems-dynamic approach that coupled C-SVATs at a 2-day resolution with a discrete event erosion–deposition model occurring with a prescribed return interval. Five possible mass-balance transformations of C occurring between the two patches were explicitly modeled: net primary production (NPP), decomposition, erosion, transport induced mineralization, and deposition. The net C-SVAT, NPP minus decomposition, exhibited three stable points of no net C flux. Starting with arbitrary initial C pool in each patch above the bifurcation point, the model approached a quasi-steady state, which included both the short-term and longer term consequences of erosion; in the baseline simulation 5080 g C m −2 was stored prior to erosion and 100 years of low intensity erosion 4840 g C m −2 SOC remained. Low intensity erosion also generated spatial heterogeneity; from an initial homogeneous distribution to 40% of the C stored in the eroded patch and 60% of the C stored in the deposition patch. Erosion reduction resulted in a corresponding increase in total soil C content that was positively related to the magnitude of erosion reduction. In conjunction with providing a modeling framework for reducing the uncertainty in C-SVAT, this model is a prototype of a growing theory of ecosystem processes within spatially explicit landscapes, a meta-ecosystem model.