Erodible Surface Research Articles

Winter variability of aeolian sediment transport threshold on a cold-climate dune

Changes in surface conditions on cold-climate aeolian dunes are pronounced; during winter dunes are wet, snow covered, and/or frozen for extended periods of time. It is unknown how the critical wind speed for sediment transport (“threshold”) varies and how threshold may influence sediment transport predictions. Although the impact of surface conditions on threshold has been examined in synthetic experiments (wind tunnels), complicated feedbacks between threshold, sand transport, and surface conditions that occur in natural environments suggest that a ground-based empirical approach may provide enhanced insight. In this study we investigate threshold variability for 73days during fall–winter–spring surface conditions from 18 November 2008 to 30 May 2009 in the Bigstick Sand Hills of Saskatchewan, Canada. Simultaneous measurements of threshold and atmospheric variables (air temperature, relative humidity, solar radiation, wind speed and direction) were used to examine the extent to which surface erodibility was regulated by meteorology. Time‐lapse images of the surface from a co-located camera were used for quality control and interpreting changes in the surface affecting threshold. Results reveal that threshold varied throughout the deployment (25–75% quartiles: 6.92–8.28ms−1; mean: 7.79ms−1). Threshold variability was especially evident at two scales: (i) event timescale and (ii) seasonal timescale. Event-scale variability peaked during mid-winter; in one event the threshold varied by 6ms−1 in 2h with freezing and re-freezing of the surface and relatively constant atmospheric conditions. The causes of event-scale variability are complex though qualitatively related to changes of wind direction, antecedent meteorological conditions, and vertical variations of grain-scale bonding agents such as pore ice and moisture. Seasonal-scale changes manifested as an increase in threshold during fall, peaking in mid-winter, and decreasing in spring. Increased threshold in mid-winter was linked to lower insolation and air temperature, suggesting low erodibility due to the presence of pore ice. Correlation coefficients of threshold versus atmospheric variables yielded relatively weak correlations (air temperature: r=−0.322; relative humidity: r=0.388; solar radiation: r=−0.309) that also varied according to wind direction, suggesting that the link between atmospheric conditions and surface erodibility on cold‐climate dunes is complex. This contrasts with results from field-based studies in warmer climates and controlled wind tunnel experiments, which show a more direct link between atmospheric variables (temperature and humidity) and surface erodibility. Nevertheless, our results do show a seasonal pattern of threshold that could be important for modeling cold-climate aeolian sediment transport.

Balkas – a new look at a common landform of the East European Plain, from a Quaternary perspective

ABSTRACTBalkas (large Quaternary gullies) of the south‐western part of the East European Plain (and their analogues in Central and Western Europe) are considered in terms of their geomorphology, lithology, sedimentology, modern surface processes, stratigraphy and palaeogeography. Features attributed to balkas in comparison with regular gullies and small river valleys are described. Balkas are widespread elements of the modern landscape with the same characteristic gentle‐concave bottom as regular gullies, and with or without weakly incised river channels. Buried gully incisions of different ages (post‐Gelasian) with the same shape are also revealed below modern Balkas. They are infilled by characteristic balka alluvial, slope and even lacustrine‐bog deposits, in places representing compound sequences of fluvial‐aeolian sedimentation. The fluvial part reflects multiple series of ephemeral episodes of increased water and sediment supply within temporary streams. Two conspicuous series supposedly fall within the final stages of the Dnieper (late Middle Pleistocene) and Valdai (Late Pleistocene) glaciations. Different ideas concerning the increase of surface runoff and erodibility of soils that might favour active balkas under conditions of land‐ice decay and permafrost, including its degradation, are discussed. The development of balkas included relatively short phases of incision and accumulation interrupted by much longer periods of inactivity, when they were subjected to surface processes in a subaerial environment or left as a relic. However, during active phases they served as important and powerful depositories and arteries of rill–gully–balka sedimentation systems, collecting and transmitting eroded material to the river valleys. These phases are related to climatic oscillations and were to some degree independent of fluvial processes affecting the permanent streams. Most of the Middle‐Late Pleistocene balkas retained their primary features, having subsequently been incorporated into the erosional network. In contrast, some of them were totally infilled and disappeared from the landscape. Copyright © 2012 John Wiley & Sons, Ltd.

Regional challenges in tourist wetland systems: an integrated approach to the Ria Formosa in the Algarve, Portugal

Coastal change and coastal erosion have been a long-existing source of environmental changes. Traditionally, regional changes in wetland systems and their relations to agriculture, industry and urbanization are a major cause for concern. Nowadays, coastal distress has reached even global proportions: the problems of coastal change are strongly linked to the loss of fragile ecosystems, eutrophication and loss of biodiversity. Given that over 70 % of all human activity is in coastal areas, it is clear that many environmental and socio-economic changes occur at a local level and manifest themselves in a spatial context. The physical effect on the geographic morphology is evident in the related consequences for land use. A deep understanding of the changes in land use, and simultaneously in coastal erosion, calls for the integrated monitoring of the most relevant effects in fragile regions. The Ria Formosa wetland system is a unique and very special wetland system in the Algarve (Portugal) and has been integrated in the NATURA 2000 network. The strong symbiosis between nature, agriculture and fisheries, as well as tourism, in the Algarve has led to spatial-ecological synergy. By using coastal recession analysis techniques by means of remote-sensed imagery from 1987, 1989, 2000 and 2007 and by combining this information with available data sets on surface erodibility, a cost surface on multitemporal transitions of land-use classes from the CORINE Land Cover data allows us to assess and integrate a decision-making framework by means of GIS. The novelty of this combined approach to land-use management is the blend of spatial analysis and remote-sensing techniques that share important information on ecosystems at risk. Our findings suggest a growing concern to the area brought by anthropogenic activity. This is studied to a spatial accounting of the distribution of land changes and transitions, where (1) a significant loss of coastal area is witnessed along the Ria Formosa, leading in particular to loss of agricultural land. (2) This loss is underpinned by an increase in leisure facilities to respond to the tourism demand of the region of the Algarve, while landscape metrics suggest that these areas are more volatile for coastal erosion. (3) Simulation through Markov chains on the land use and effects of urban, agricultural, forest and wetland dynamics suggests that by 2026, it is expected to continue to have an increase in urban land, leading to an augmented vulnerability of coastal erosion processes brought by the loss of forest areas which protect from erosion given the root system that directly protects from the existing wave energy and helps sedimentation processes. The above methodology and the availability of data that are freely available render such a combined approach interesting for many other regions of the world, where tourism, coastal change and regional balance are of the utmost importance for sustainable development. The advanced research tools presented here are of critical importance for coastal zone degradation management.

The use of a new portable erosion measuring device for assessing the erodibility of the surface layers of flood embankments

AbstractWhen a river overtops its flood banks, water running down the landward side of the bank can rapidly erode the soil surface and scour the bank, sometimes leading to breaches and collapse. A covering of living vegetation, particularly grass, can reduce this risk of water erosion. As part of a project to assess the effectiveness of different management regimes on bank vegetation cover, direct measurements were required of the erodibility of the soil surface. A portable erosion measurement device (EMD) was developed by LAB Coastal with the support of the Environment Agency. This could direct water flowing at known velocities across areas of the flood banks, and it was used to test directly the erosion resistance of vegetated grass banks at three sites. The EMD gave a direct measure of the erodibility of a small sample of flood bank. While measurements of soil strength and assessments of vegetation cover were useful, they did not always correctly characterize the stability of the bank surface as measured directly by the EMD. The EMD and its use are described and the results obtained are discussed. The results indicate that flood banks need to be mown at least once a year to make them less vulnerable to erosion.

Total suspended particulate matter emissions at high friction velocities from desert landforms

[1] Most wind erosion studies that characterize dust emission potential measure particulate matter smaller than 10 mm (PM10) for air quality purposes or atmospheric modeling. Because the PM10 size fraction is only a portion of the total range of fine‐grained particles potentially emitted from desert landforms, we modified the miniature Portable In Situ Wind Erosion Lab (PI‐SWERL) by adding a new instrument to measure total suspended particulate matter (TSP). The modified PI‐SWERL is capable of measuring TSP with diameters <500 mm emitted from highly erodible surfaces at friction velocities up to 1.28 m s −1 . Undisturbed and artificially disturbed surfaces of six common landforms in the Negev Desert of Israel were studied to evaluate the utility of TSP measurements. These landforms include alluvial fans and plains armored by desert pavements, loessial soils with silt‐rich surficial crusts, fluvial loess with biological crusts, and active sand dunes. The landforms differ in character and surface age, thereby exhibiting a wide range of surface covers, soil properties, and soil strengths. Our results indicate that the magnitude of TSP emission is primarily controlled by geomorphic setting and surface characteristics. TSP and PM10 concentrations measured from dust‐rich loessial soils were significantly correlated, and TSP emission was best predicted at all sites using PM10 content and bearing capacity. Our results demonstrate that further research is needed to determine correction factors for friction velocities related to erodible, anisotropic surface roughness elements and that the modified PI‐SWERL is a promising tool to quantify total potential emission flux from desert landforms.

Assessment of extreme wind erosion and its impacts in Inner Mongolia, China

Abstract Increasing land use intensity in the Xilingol Steppe has changed a former dust deposition area into a vulnerable area against wind erosion. Overgrazing caused large-scale soil degradation and destruction. The use as cropping land affects only a small area, but especially these parts of the steppe are extremely endangered. Strong winds, bare soil surface and high soil erodibility caused extreme wind erosion in April and May 2006 on a 147 ha fallow cropping field. The size and thickness of the deposited material in a sediment fan was measured to calculate the volume and the mass of the relocated material. The average thickness, the total size and the volume of the sediment fan were 11 mm, 257 ha and 27,600 m3, respectively. Comparison of the grain size distributions of soil and sediment material showed that up to 45,900 m3 of surface soil material were moved by wind and up to 18,300 m3, largely of the clay and silt fractions, were removed by dust emission. The average erosion rate from the cropped field was between 323 and 340 t ha−1, which was equivalent to 30 mm of the upper soil surface. The average dust production at the field amounted up to 136 t ha−1. Croplands are thought to contribute considerably to the total dust production and soil degradation in the temperate grasslands of Inner Mongolia. The sediment fan consisted predominantly of sand. This accumulation of coarse particles at the surface of the cropping and grassland locally degraded soil quality.

Response of Soil Suction to Heavy Rainfalls in a Tailings Dam

Rainfall is a significant factor leading to failure of tailings dams. The impact of rainfall on the instability of dams is mainly reflected in the variation of negative pore-water pressure (i.e. matric suction) during rainfall infiltration. However, there is a lack of study on the effects of rainfall on suction in tailings dams. In this study, the response of suction to artificial heavy rainfalls in a tailings dam was investigated. The effects of rainfall intensity and surface vegetation conditions on the response of suction were studied. It is found that suctions at a certain depth in the tailing dam were kept constant until the wetting front reached this depth. Once suctions were altered, the values dropped rapidly. The magnitude of suction change generally decreased with depth. Rainfall infiltration mainly occurred above the depth of 40 to 80 cm when subjected to rainstorm and heavy rainstorms. Larger rainfall intensity leads to shorter response time and to larger depth affected by rainfall, implying that the tailings dam is more susceptible to shallow landslide failure under larger rainfall intensity. The existing vegetation increases infiltrability significantly and then produces an adverse effect on the stability of the tailings dam. On the other hand, it is observed that the presence of vegetation greatly prevented surface erodibility and then decreases the possibility of debris flow.

Innate immune responses to polyanhydride nanoparticles modified with a toll like receptor three ligand. (52.9)

Abstract Improving efficacy of subunit-based immunization protocols without eliciting adverse reactions continues to be a hurdle in vaccine design. Vaccination of mice in our laboratory with surface eroding polyanhydride nanoparticles (NPs) prepared from 1,6-bis(p-carboxyphenoxy)hexane (CPH) and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) administered as a single intranasal dose provided high-titer and high-avidity humoral responses and protection against a live Yersinia pestis challenge at 23 weeks post-vaccination. The goal of the current study was to elucidate the immune-enhancing properties of the NPs by functionalizing them with TLR3 ligands (i.e., poly I:C) via either surface modification or encapsulation into the particle in order to activate macrophages. We also tested the hypothesis that the protective responses observed following intranasal NP vaccinations was due to particles undergoing endocytic processing by targeting TLR3 located on the endosomal membrane. Our results demonstrated that stimulation of primary macrophages (bone marrow-derived) with poly I:C modified particles increased surface expression of MHC II and CD80/86 as well as enhanced secretion of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α as compared to stimulation with non-functionalized NPs. Encapsulation of TLR ligands in polyanhydride NPs enhanced the activation status of macrophages and targeted functionalization may improve the efficacy of this novel vaccine platform.

Energy-Based Method for Providing Soil Surface Erodibility Rankings

The jet erosion test (JET) and the hole erosion test (HET) are two tests used to determine soil erodibility classification, and results are commonly interpreted by two distinct methods. A new method based on fluid energy dissipation and on measurement of the eroded mass for interpreting the two tests is proposed. Different fine-grained soils, covering a large range of erodibility, are tested. It is shown that, by using common methods, the erosion coefficient and average critical shear stress are different with the JET and with the HET. Moreover, the relative soils classifications yielded by the two erodimeters are not exactly the same. On the basis of the energy method, an erosion resistance index is determined for both apparatuses, and a classification of surface-erosion resistance is proposed. For both apparatuses, values of the erosion resistance index are roughly the same for each soil, and a single classification of soil erodibility is obtained.

Effect of nonerodible grains on wind erosion control

A simple drag partition scheme for rough surfaces of various roughness densities is presented to explain the effect of roughness density on apparent threshold friction velocity, the validity of which is confirmed by comparison with measured data sets. Based on this drag partition scheme, we assume that the presence of nonerodible rough grains affects the wind erosion of an erodible surface in two ways: (1) protecting part of the erodible underlying surface from wind erosion by directly covering it and (2) leading to a decrease of the shear stress acting on the uncovered part of the erodible underlying surface by absorbing some wind momentum. Involved with the two hypotheses, a mathematical formula with an exponential form that describes the dependence of mass erosion rate on the free‐stream wind velocity and the roughness density is developed by dimensional analysis. The mathematical formula of wind erosion rate fits well some data sets of laboratory experiments and field observations.

Numerical modelling of aeolian erosion over rough surfaces

AbstractThe presence of non‐erodible roughness elements on erodible surfaces has the effect of absorbing part of the wind shear stress and thus protecting the erodible surface from wind erosion. This paper examines the shear stress distribution over roughness arrays of varying density, representing the progress of erosion on a bed of erodible and non‐erodible particles. Three‐dimensional numerical simulations, simulating wind flow over a bed of particles covered by roughness elements, were conducted in order to investigate the effect of roughness elements on the shear stress near the surface. The results of these simulations confirm that the erosion of soil by wind is strongly attenuated by the presence of roughness elements on the surface and depends on the geometric properties of the roughness elements. Based on the new numerical results obtained, a refinement of existing theoretical approaches is developed to describe the dependence of the friction velocity upon roughness frontal area and real exposed cover rate. The new formulation proposed will allow a more accurate evaluation of shear stress partitioning as a function of topographic changes. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A review of the application of the fetch effect to modelling sand supply to coastal foredunes

The fetch effect is an increase of the aeolian sediment transport rate with distance downwind over an erodible surface. The first observations of the fetch effect go back 70 years and the concept has been widely used in a variety of landscapes. This paper reviews the present state of knowledge of the fetch effect, with particular reference to its application in coastal areas, and compares findings from theoretical, wind tunnel, and fieldwork experiments. While wind tunnel experiments tend to show critical fetch distances of a few metres, studies in natural areas show that measured critical fetch distance can exceed one hundred metres. There is supporting evidence pointing to the role of soil clods/crusts and moisture content in increasing critical fetch distances in agricultural and coastal areas, respectively. In coastal areas tradeoffs imposed by the geometry of the beach over which the wind is blowing and wind direction determine the available fetch distance and thus the sediment transport rate downwind. A major challenge which needs to be addressed is the development of robust equations for predicting both the critical fetch length and the increase in the sediment transport rate with distance on beaches. There is also a need to obtain field data on the combined effect of moisture, angle of wind approach, beach width, and fetch length. Long-term monitoring using remote sensing techniques may provide valuable data to analyze the effect of fetch distances on the nature of transport events that deliver sediment from the beach to the foredune.

Depot versus dispersal: biodegradable polymer vaccination effects of size and chemistry (46.17)

Abstract Development of safe and efficacious vaccine regimen including delivery vehicles, routes, and adjuvants is paramount to public health and preventive medicine. This study evaluated the whole body distribution of unique, surface eroding polymers prepared from aliphatic sebacic acid (SA) and aromatic 1,6-bis(p-carboxyphenoxy)hexane (CPH). The inherent surface erosion kinetics permit development of a single dose vaccine based on tailored release kinetics of immunogen, adjuvanticity and sparing of protein dose, and sustained antigen presentation. Fabrication methods were used to create a size range (400 nm to 10 µm) of particles encapsulating LSS 640 fluorophore. These particles were used to evaluate in vivo distribution following intranasal (IN) or subcutaneous (SC) administration to mice. Using live animal imaging at multiple time points, fluorescent analysis at the injection and distal anatomical sites establish that microparticles distributed in a pattern consistent with a depot effect that was dependent upon the injection route. In contrast, nanoparticles distributed systemically regardless of route. Ex vivo analysis of excised tissues verified nanoparticle distribution to distal sites. The ability to assess the depot and dispersal effect of this novel delivery platform in real time consequent to the induction of an antibody response will provide insight into how size and polymer chemistry can be used therapeutically to effect targeting of a vaccine to desired immune tissues.

A mixture model for water uptake, degradation, erosion and drug release from polydisperse polymeric networks

We introduce a general class of mixture models suitable to describe water-dependent degradation and erosion of biodegradable polymers in conjunction with drug release. The ability to predict and quantify degradation and erosion has direct impact in a variety of biomedical applications and is a useful design tool for biodegradable implants and tissue engineering scaffolds. The model is based on a finite number of constituents describing the polydisperse polymeric system, each representing chains of an average size, and two additional constituents, water and drug. Hydrolytic degradation of individual chains occurs at the molecular level and mixture constituents diffuse individually accordingly to Fick's 1st law at the bulk level – such analysis confers a multi-scale aspect to the resulting reaction–diffusion system. A shift between two different types of behavior, each identified to surface or bulk erosion, is observed with the variation of a single non-dimensional parameter measuring the relative importance of the mechanisms of reaction and diffusion. Mass loss follows a sigmoid decrease in bulk eroding polymers, whereas decreases linearly in surface eroding polymers. Polydispersity influences degradation and erosion of bulk eroding polymers and drug release from unstable surface eroding matrices is dramatically enhanced in an erosion-controlled release.

Fluvial Sedimentary Patterns

Geomorphology is concerned with the shaping of Earth's surface. A major contributing mechanism is the interaction of natural fluids with the erodible surface of Earth, which is ultimately responsible for the variety of sedimentary patterns observed in rivers, estuaries, coasts, deserts, and the deep submarine environment. This review focuses on fluvial patterns, both free and forced. Free patterns arise spontaneously from instabilities of the liquid-solid interface in the form of interfacial waves affecting either bed elevation or channel alignment: Their peculiar feature is that they express instabilities of the boundary itself rather than flow instabilities capable of destabilizing the boundary. Forced patterns arise from external hydrologic forcing affecting the boundary conditions of the system. After reviewing the formulation of the problem of morphodynamics, which turns out to have the nature of a free boundary problem, I discuss systematically the hierarchy of patterns observed in river basins at different scales.

Development of a dust source database for mesoscale forecasting in southwest Asia

Numerous high‐resolution (1 km or better) images from satellite remote sensing platforms, i.e., space shuttle, Sea‐viewing Wide Field‐of‐view Sensor, and the Moderate Resolution Imaging Spectroradiometer, show dust plumes at the scale of 100 km originate from the merging of a multitude of point source plumes. These point source plumes stem from numerous point sources measuring 1–10s km across. Capitalizing on the Naval Research Laboratory's recently developed satellite derived 1‐km Dust Enhancement Product (DEP) imagery we can readily distinguish elevated dust over land from other components of the scene and identify the many small, eroding point sources that form the heads of point source plumes. On the basis of this approach, a high‐resolution (1‐km) dust source database (DSD) is created using 5 years (2001–2005) of DEP imagery for southwest Asia. The performance of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) using the high‐resolution DSD is evaluated via a case study of a major dust event over Afghanistan, Iran, and Pakistan in October 2001. The results from our case study show that the improved specification of erodible land surfaces by use of a high‐resolution DSD allows COAMPS to accurately model the evolution of individual dust plumes and better forecast the onset and end of dust storm occurrence (i.e., low‐visibility conditions). Statistical analyses of the visibility predictions and dust storm occurrence show simulations using the high‐resolution DSD have the lowest false alarm rates and the highest total prediction skill among the other DSDs that were considered. This work contributes to the growing base of knowledge concerning the global dust cycle by identifying and mapping point sources in one of the world's foremost dust‐producing regions.

Numerical modeling of 2‐D granular step collapse on erodible and nonerodible surface

The study of the collapse of a granular step is of great interest for understanding transient dense granular flow conditions and for modeling geophysical flows in granular materials. We present the results of a series of finite elements simulations considering variable column aspect ratios and properties for an elastoplastic material with a Mohr‐Coulomb yield rule and nonassociate flow rule. The adopted approach does not suffer limitations of typical shallow water equation methods, being able to consider strong vertical motion components. Transition from initial instability to complete flow development is simulated for columns with different aspect ratios (a ≤ 20). Simulation results are compared to original tests and available well‐documented experimental data, in terms of flow development, duration, profile geometry, velocity distribution, erosion and deposition, and evolution of the interface between static and moving material. Tests involving a thick erodible layer have been performed and numerical simulation results are compared also with a real case study. Numerical results support both those of qualitative and theoretical models and the proposed general scaling laws and clarify the dependence on frictional properties. Power laws describe the normalized runout versus aspect ratio (a &gt; 4) relationship with constants of proportionality dependent on internal friction angle and exponents ranging between 0.68 and 0.77, in good agreement with experimental results. Total duration and evolution in three successive phases agree with observations. Time for the flow front to cease motion with respect to aspect ratio is best represented by the 3.68a0.448 relationships for a 30° internal friction angle material.

In Situ Erosion Testing and Clay Levee Erodibility

Earthen levee damage from storm surge overtopping in the New Orleans area was observed and documented after Hurricane Katrina. Some levee reaches were undamaged and some were slightly eroded, while other portions were completely breached. The in situ jet index test method was applied along selected post-storm reconstructed levee reaches to assess levee fill erodibility. Jet index testing was also conducted at three undamaged (un-eroded) levee surface locations. Pre-storm levee profiles (elevations) were compared to post-storm modeled stormwater elevations to estimate overtopping depths at the test sites. Also, pre-storm levee profiles were compared to post-storm profiles to estimate erosion depths at the test sites. The jet index test results were integrated with pre-storm soil boring data (i.e., stratigraphy and soil classification), post-storm erosion depths, and overtopping depths to investigate soil surface erodibility relationships. The results showed the validity of using the jet index test method for levee soil erodibility assessments.

A unified mathematical model for the prediction of controlled release from surface and bulk eroding polymer matrices

A unified model has been developed to predict release not only from bulk eroding and surface eroding systems but also from matrices that transition from surface eroding to bulk eroding behavior during the course of degradation. This broad applicability is afforded by fundamental diffusion/reaction equations that can describe a wide variety of scenarios including hydration of and mass loss from a hydrolysable polymer matrix. Together, these equations naturally account for spatial distributions of polymer degradation rate. In this model paradigm, the theoretical minimal size required for a matrix to exhibit degradation under surface eroding conditions was calculated for various polymer types and then verified by empirical data from the literature. An additional set of equations accounts for dissolution- and/or degradation-based release, which are dependent upon hydration of the matrix and erosion of the polymer. To test the model's accuracy, predictions for agent egress were compared to experimental data from polyanhydride and polyorthoester implants that were postulated to undergo either dissolution-limited or degradation-controlled release. Because these predictions are calculated solely from readily attainable design parameters, it seems likely that this model could be used to guide the design controlled release formulations that produce a broad array of custom release profiles.

Erosion resistance of cohesive soils

This paper presents experimental results on surface erodibility tests performed with undisturbed and remolded samples of cohesive soils. When subjected to shear stress caused by flowing water, erosion occurs in two distinctive modes: particle erosion and mass erosion. Erosion resistance is defined as the applied bed shear stress at which incipient erosion occurs. The ratio of mass erosion to particle erosion resistance ranged from 3.7 to 5.4 for the undisturbed samples. The erosion resistance increased with increase of moist bulk density, and an increase of water content to a certain level (to be termed optimum condition hereafter) and the decrease of the mean sediment size.Water content, plasticity index, and moist bulk density of a soil sample are combined into a single parameter ?. Results of the tests on field samples show that ? and the non-dimensional erosion resistance follow linear relationship. In the erodibility tests of remolded samples, individual soil property was changed to investigate its effect on erosion resistance. The results of the tests on remolded samples show that both normalized particle and mass erosion resistance could be represented by a Gamma distribution of ? with the maximum resistance occurring under a condition that closely resembles the field condition in terms of moist bulk density and water content. An erosion model is presented that can be used to estimate the particle and mass erosion resistance from the measured water content, plasticity index, and the moist bulk density of a cohesive soil sample.