Bank Stability And Toe Erosion Model Research Articles

Dynamic Analysis of Changes in Jambu Riverbed and Banks: Case Study Around Cikuya Bridge

Several cross-sections of the Jambu River, particularly around the Cikuya Bridge, have experienced bank collapse phenomena. This paper interprets the issues related to bank collapse and its impact on the flow capacity of the Jambu River, especially around the Cikuya Bridge. Morphological changes were simulated using a sediment transport model implemented in the Hydrologic Engineering Center's River Analysis System (HEC-RAS) 6.3.1, integrated with the ARS-USDA Bank Stability and Toe Erosion Model (BSTEM). The simulation results indicate that over a period of 10 years, the thalweg elevation (the lowest point of a riverbed) of the Jambu River around the Cikuya Bridge is predicted to experience deposition in 17 cross-sections and erosion in 15 cross-sections. The highest deposition occurs at the cross-section below the Cikuya Bridge, with a thalweg elevation change of 0.59 m. This warrants attention as the storage capacity of the cross-section decreases by 7% from the initial condition. Predictions indicate that bank collapse will occur in 7 cross-sections over the next 10 years. This is attributed to the steep slopes of silt and clay banks, exceeding 45 degrees, and the reduced safety factor of bank stability due to groundwater pressure influenced by river discharge fluctuations and tidal effects reaching the Jambu River. Bank collapse impacts the elevation change of the riverbed and adds load to the sediment transport model from the collapsing cross-sections to the downstream sections. Keywords: Jambu River, Cikuya Bridge, Cilacap, sediment transport, bank stability and toe erosion model

Quantifying the Impact of Model Selection When Examining Bank Retreat and Sediment Transport in Stream Restoration

The objective of this study was to assess the performance of form-based and process-based models, and of local-scale and reach-scale models, used to examine bank retreat and sediment transport in stream restoration. The evaluated models were the Bank Erosion Hazard Index (BEHI), Bank Assessment for Nonpoint Source Consequences of Sediment (BANCS), Bank Stability and Toe Erosion Model (BSTEM), and HEC River Analysis System (HEC-RAS 1D). Model-to-model assessments were conducted to quantify the impact of model selection when predicting applied stress and geomorphic change in a restored stream in North Carolina, USA. Results indicated that the mobility of the bed dictated model selection at the reach-scale. The process-based HEC-RAS 1D was needed to accurately analyze the sand-bed stream, predicting amounts of geomorphic change comparable to measured data and up to three orders of magnitude higher than those from local-scale models. At the local-scale, results indicated that the bank retreat mechanism and flow variability constrained model selection. The form-based BEHI and BANCS did not directly account for geotechnical failure nor capture severe floods, underpredicting amounts of geomorphic change by an order of magnitude when compared to the process-based BSTEM, and failing to characterize erosion potential and applied stresses after short-term morphodynamic adjustments.

Refining the Bank Stability and Toe Erosion Model: Improving the timestep, the top of toe selection and the iteration routine

AbstractRiverbank failure is an essential source of river sediment and a major cause of river meandering. The Bank Stability and Toe Erosion Model (BSTEM) is a widely used simulation tool owing to its simplicity and clear presentation of results. However, the three core issues in the simulation by the software, time‐step determination, top‐of‐toe (TT) selection, and the iterative algorithm, still lack an in‐depth discussion to ensure the rationality and stability of the simulation results. In this study, the Jing‐150 cross‐section of the Jingjiang River was chosen as an example to illustrate these three problems. For the first problem, which is the choice of the time step, the simulation results become stable and close to the measured value as the time‐step decreases. After determining a suitable time step, the difference between adopting and modifying the default TT of the BSTEM was analysed. The results show that adopting the default TT causes chaos in the distribution of profile nodes, leading to an overly large bank failure width, whereas the modified TT node distribution is normal and the bank failure width is close to the measured value. For the third problem, the original iteration routine (OR) may cause the output bank profile to be unstable and cause a deviation between the bank width and measured value. The negative impact of unstable bank profiles diminishes as the time‐step decreases. However, the workload for reducing the time step is enormous. Therefore, an improved routine (IR) was proposed. With IR, the relative error between the simulated and measured values of the failure width was within 15% when the SD of the water stage was reduced to 0.2478. A similar result could only be obtained when the SD of the water stage was less than 0.099 for OR. This means that to obtain the same simulation accuracy for the failure width, IR can use a larger time step than OR, thereby reducing the workload of the simulation.

Field Measurements and Modelling of Vessel-Generated Waves and Caused Bank Erosion—A Case Study at the Sabine–Neches Waterway, Texas, USA

The Sabine–Neches Waterway (SNWW) is home to the largest commercial port of the United States military and of the refineries that produce 60% of the nation’s commercial jet fuel. The deposited sediments from bank erosion due to wake wash result in frequent dredging to keep the waterway operational. This study investigates vessel-generated waves and their impacts on bank erosion. Surface wave data at Golden Pass and the City of Port Arthur Park dock were measured using a 1 MHz Aquadopp Profiler. Bank properties such as soil strengths were measured and soil samples were collected. Acceptable predictive models for estimating the maximum wave heights caused by vessels sailing through the SNWW were developed and validated with recorded data. Vessel-generated waves are found to produce enough shear forces to mobilize bed sediments and cause bank erosion. The bed erosion rate increases with an increase in wave height or a decrease in water depth. Bank and bank toe erosion occurs at both monitoring locations. Bank stability and toe erosion model (BSTEM) results suggest that potential bank protection options are large woody debris and riprap at Port Arthur. However, other stronger stabilization methods are required at Golden Pass.

Effects of desert riparian vegetation roots on the riverbank retreat process in the Tarim River in China

The desert riparian vegetation zone is an important part of the riparian ecosystem. It is significant for river evolution and to channel beds owing to the reinforcement effect of the vegetation roots on the bank and resistance to erosion. The quantitative effects on toe erosion and bank collapse were first investigated to determine how vegetation roots affect the continuous retreat process of riverbanks under different water levels. The case study is the Tarim river, the degrees of riverbank stability at eight sampling sites during the 2016 and 2017 hydrological years were calculated using the bank stability and toe erosion model (BSTEM). Furthermore, the effects of six vegetation species, Populus euphratica (PE), Tamarix ramosissima (TR), Alhagi sparsifolia (AS), Nitraria tangutorum (NT), Phragmites australis (PA), and Glycyrrhiza uralensis (GU), on riverbank stability were discussed. Taking the right bank of sampling site II (Alar New Bridge) as an example, the bank stability safety factor (Fs) and collapse process under the roots of six vegetation species with different root area ratios (RARs) were calculated. The following conclusions were drawn from the results: (a) Different vegetation roots can reduce toe erosion from 0.4 % to 68.4 %, with peak effects during the dry season and recession stages; (b) The presence of near-bank vegetation roots can strongly influence bank collapse, particularly during the recession stage when water level drops rapidly; and (c) Most of the calculated Fs with the roots of all six plant species studied were higher than those without roots during four stages. Moreover, it was greater than the critical value of 1.3 in most cases. The results also indicate that banks with PE roots had the highest Fs values. By contrast, banks with NT and GU roots had the smallest Fs. As the RAR increased, the Fs values in a hydrological year increased linearly for each vegetation specie. The rate of increase order was as follows: PE > TR > NT > AS > PA > GU under a particular range of RAR (0.9 % < RAR < 1.8 %).

Quantitative analysis of riverbank collapse mechanisms based on BSTEM

ABSTRACT Riverbank collapse is a very common phenomenon in natural rivers that plays an important role in their evolution. In this study, we used the Bank Stability and Toe Erosion Model (BSTEM) to study quantitatively the effects of soil properties and bank inclination on its stability. For this, we investigated the stability of homogeneous banks under different bank inclination angles and binary structure banks composed of different materials. Our findings show differences between the cohesive and non-cohesive bank collapse modes, under the condition of ignoring the water table. We find the internal friction angle to be the dominant factor affecting non-cohesive banks, whereas cohesive banks are affected by the effective cohesion. The safety factor and water depth variations follow a quadratic polynomial law, more pronounced in non-cohesive banks. A higher inclination reduces the riverbank stability and safety factor. The latter is sensitive to bank slope changes for larger effective internal friction angles in non-cohesive banks. The material composition and thickness of the upper and lower layers of the riverbank with a binary structure affect the bank stability. The thickness and mechanical properties of the lower material play a key role in riparian stability.

An integrated assessment of land use impact, riparian vegetation and lithologic variation on streambank stability in a peri-urban watershed (Nigeria)

Bank erosion is an important source of sediment and phosphorus to inland fluvial systems and is generally responsible for more than half of the total watershed sediment export. Numerous studies have quantified bank erosion and the spatio-temporal variation of sediment flux in different watersheds. However, there is sparse research to date on the linkages between bank erosion/accretion and sediment export under different land uses, especially in rapidly evolving peri-urban watersheds. This research, therefore, integrated remote sensing techniques and repeated field survey of erosion pin plots to quantify bank erosion and sediment flux in the 80 km2 Nkisi River watershed (NRW), southeast Nigeria, over a three-year period. The impact of land use change on streambank erosion was evaluated by utilising remotely sensed Landsat datasets of 2003, 2010, 2016 and 2019. Geotechnical tests were used to characterise the lithologic properties of the banks, while the Bank Stability and Toe Erosion Model (BSTEM) was used to determine the stability of the banks under various hydrological conditions and mechanical properties of the riparian vegetation. Mean bank recession rates increased from 10.7 cm during the 2017–2018 monitoring period to 17.5 cm for the 2019–2020 monitoring period. The percentage of total watershed export ascribed to bank erosion in the three stream reaches varied from 6.6 to 44.9%. The high rates of bank erosion and accretion within the NRW were attributed to rapid changes in land use, which evolved from grassland and woodland to cropland, built-up and bare land. The BSTEM accurately predicted the high erosion rates of the streambanks and showed that riparian vegetation has a mechanical effect on bank stability. However, the mechanical effect diminishes as the depth to water table rises during high streamflow events.

Variable discharges control composite bank erosion in Zoige meandering rivers

This study investigated the roles of variable daily discharges in controlling processes of composite bank erosion in alpine meandering rivers located in the Zoige basin on the Qinghai-Tibet Plateau of China using Bank Stability and Toe Erosion Model (BSTEM). BSTEM was calibrated from compiled daily discharges, field measurements, and pre-determined model parameters for modeling fluvial erosion (FE) and bank collapse (BC) in the lower layer of a conceptualized composite bank profile. Modeling was based on theoretically designed five sets of competent hydrographs, each of which contains seven hydrographs with the same mean daily discharge (Qa) and variable shapes represented by different combinations of the initial daily discharge, the peak daily discharge, and its occurrence time. The design was guided by 77 real competent hydrographs representing daily discharges recorded in 14 years. Results showed that shapes of these hydrographs (1) had discernable impact on FE and BC, but this impact is secondary to that of Qa; and (2) affected FE in magnitude, but BC in both magnitude and frequency. After identifying a proportion of the designed hydrographs that are realistic in the existing flow regime, hydrograph-based rating curves for both FE and BC were established and used to create hydrograph-based effective discharges (Qe) for FE and BC, respectively. Finally, Qe was correlated to the width of overhanging arm for explaining the dominant processes controlling composite bank erosion and linking the nature of these processes to lateral migration of the associated meandering rivers. This success demonstrates a great potential of using Qe to reveal many complex processes in fluvial systems.

Assessment of land use impact and seepage erosion contributions to seasonal variations in riverbank stability: The Iju River, SW Nigeria

The Iju (Atuwara) River is an important component of the Owo River catchment (ORC), which supports the livelihood of millions of people in Lagos and Ogun States of southwestern Nigeria. However, rapid urbanisation and numerous anthropogenic activities have caused significant changes in the natural flow regime of the river, resulting in serious bank erosion. In many riparian areas, accelerated bank erosion has been attributed to the combined effects of seepage erosion and fluvial undercutting of the bank toe due to the hydraulic stress of the river on the bank. This research, therefore, investigated the combined effects of seepage erosion, riparian vegetation (root cohesion), tension crack, and land use/land cover (LULC) change on the stability of riverbanks on the Iju River, Nigeria. Multi-temporal LULC datasets acquired from remotely sensed Landsat images of 1999, 2009, and 2019 were used to map LULC changes in the ORC. Laboratory tests were conducted to determine the geotechnical properties of the riverbanks followed by bank stability analysis and evaluation of the erosion potential of the riverbanks using the Bank Stability and Toe Erosion Model (BSTEM) and Bank Erosion Hazard Index (BEHI), respectively. The BSTEM results indicate that the factor of safety (Fs) decreased with an increase in seepage undercutting distance (du), irrespective of the bank angle. The correlation of Fs with root cohesion (cr) and depth of tension crack (zc) shows that Fs was positively correlated with cr but decreased with an increase in zc. LULC change results show that the natural flow regimes of rivers within the ORC have been adversely affected by the combined decrease in vegetation and wetlands, with a corresponding increase in the spatial extents of the built-up area and cultivated land/open spaces. These research findings are essential for the development of a watershed-scale natural disaster management framework for the southwest ecoregion of Nigeria.

Evaluating stream bank instability and toe erosion using BSTEM model for the Amu river

Loss of land, disputes on sharing costs, and benefits of transboundary waterways are points of debate between neighboring countries. Unfortunately, weak, undeveloped countries always suffer more than their stronger neighbors. Due to economic, political, and institutional problems, Afghanistan is one country that faces challenges to develop the potential of its water resources. Each year, Amu River flooding causes great losses of land due to massive bank degradations and erosions for up to several kilometers. Currently little progress has been made to study, research, or manage the bank erosions of the Amu River. In the absence of field data, the Bank Stability and Toe Erosion Model (BSTEM) may be used to analyze stream bank stability and toe erosion. This study was conducted to describe the Amu River stream bank using the BSTEM model for a restoration process. A field survey was conducted from February 3, 2019, to February 23, 2019; soil type, layer thickness, water table depth, and stream bank profile are entered into the BSTEM model with two different flow depths according to insights from villagers and well-diggers. Mass failure and toe erosion are two dominant mechanisms of Amu River bank failure, and the effectiveness of vegetation on bank protection is observed.

Bank stability and toe erosion model as a decision tool for gully bank stabilization in sub humid Ethiopian highlands

Gullies that are expanding at alarming rate are responsible for the majority of soil losses in the (sub) humid highlands of Ethiopia. Few affordable and effective methods for gully erosion control are available in the highlands. The objective of the study was to develop cost-effective measures to halt gully expansion by determining stable-bank conditions under a variety of environmental situations using the Bank Stability and Toe Erosion Model (BSTEM). The study was carried out in the sub humid Debre Mawi watershed, located 30 km south of Lake Tana. Input data for the BSTEM model were collected using field surveys and soil sampling. After the BSTEM was tested on actual measured soil data, soil cohesion and internal friction angle were calibrated against observed gully bank retreat. Using the calibrated parameters, the model evaluated the stabilization of the existing gully bank under different scenarios in which groundwater table, bank angle and bank height, tension crack depth, vegetation, and toe protection were varied. Finally, the head-cut of the study gully was treated based on the model recommendation. The simulated results showed that a 5 m deep gully was stable under fully saturated conditions when the bank toe is protected, its upper surface is vegetated, and its bank angles do not exceed 45°. If the depth of the gully is less than 5 m or if its water table is deeper than 0.5 m, only regrading the gully bank to an angle of 45° can stabilize the gully. BSTEM showed to be an effective tool that can be used to evaluate gully control measures.

Effects of riparian plant roots on the unconsolidated bank stability of meandering channels in the Tarim River, China

Meandering channels with highly sinuous and distorted bends have developed along the middle and lower reaches of the Tarim River in northwestern China. Riverbanks composed of unconsolidated materials have much lower bank strengths and are susceptible to fluvial erosion and bank collapse, particularly under high flow conditions. Thus, the formation and development of meander bends in such environments appear unintuitive. It is logical to speculate that riparian plant roots in unconsolidated banks have significant effects on bank stability and bend development in the absence of cohesive sediments, but this has not been verified. To determine the influence of root cohesion on the bank stability of meandering channels in the Tarim River, in situ measurements and sampling of roots from locally dominant riparian vegetation, i.e., Populus euphratica (PE), Tamarix ramosissima (TR), and Phragmites australis (PA), were conducted on the meandering bends to obtain root parameters, including diameter and root area ratio. The radius of curvature of local bends corresponding to sampling sites was also calculated using remote sensing imagery. We used the Bank Stability and Toe Erosion Model (BSTEM) to quantitatively estimate the effects of different root conditions on channel bank strength. The results confirmed that roots (and sand–root composites) provide effective reinforcement to unconsolidated banks, control the bank erosion, and hence enhance bank stability. However, the effects were highly variable under different root conditions. PA roots generally improved bank strength more than those of PE or TR, with PA, PE, and TR improving bank strength by 88.2%, 73.2%, and 63.6%, respectively. Riparian vegetation in this extremely arid and unconsolidated sediment environment therefore appears to be a prerequisite for sustaining the meandering channel.

Mechanisms of riverbank failure and channel instability on the Nkisi River, Southeast Nigeria

Sedimentation hazards pose several geoenvironmental problems in active alpine regions and fluvio-deltaic environments. Therefore, this research seeks quantitative knowledge of the mechanisms that trigger riverbank erosion which result in high volumes of sediment yield in the downstream reaches of the Nkisi River. Study of the mechanisms of mass wasting of the riverbanks was motivated by the high rate of siltation and accretion that are currently occurring at the mouth of the Nkisi River, occupying a total surface area of about 40,000 m2. Many riverbank stability and erosion assessment studies have been done using a wide range of geomorphometric and geotechnical analyses which consider the shear strength of the bank materials in relation to the geomorphometric characteristics of the riverbanks. With this insight, this research focuses on investigating the potential causes of riverbank retreat on the river, with particular interest on the effects of soil properties in triggering mass failures. Field surveys and laboratory investigations, coupled with Bank Erosion Hazard Index (BEHI) and Bank Stability and Toe Erosion Model (BSTEM) characterized the riverbanks as unstable and conditionally stable, revealing a potentially high rate of sediment loading from the composite banks, with a factor of safety that varies from 0.76 to 1.04.

Monitoring of riverbank stability and seepage undercutting mechanisms on the Iju (Atuwara) River, Southwest Nigeria

This paper presents the results of a monitoring programme designed to investigate the inherent factors contributing to channel instability and riverbank erosion on the Iju River, Southwest Nigeria. Detailed reconnaissance surveys and in situ measurements were used to determine the geomorphometric characteristics of the riverbanks at more than 15 locations along the river channel. Laboratory tests in combination with the Bank Stability and Toe Erosion Model (BSTEM) and Bank Erosion Hazard Index (BEHI) were conducted to determine the shear strength characteristics and erosion potential of the riverbanks. The BSTEM results indicate that the factor of safety (FS) decreased from the initial values of 2.64 and 4.42 to 1.09 and 0.51, respectively. Further correlation of FS with root depth and depth of tension crack showed that FS was positively correlated with root depth but decreased with an increase in the depth of tension crack. The high BEHI values of 26 and 32 gave credence to the assumptions regarding the high erosion potential of the Iju riverbanks. These research findings are essential for the development of a watershed-scale natural disaster mitigation plan for the Southwest region of Nigeria.

Quantification of river bank erosion by RTK GPS monitoring: case studies along the Ningxia-Inner Mongolia reaches of the Yellow River, China.

The Ningxia-Inner Mongolia reaches of the Yellow River suffer from bank erosion problems; in order to identify the bank erosion dynamics, Real Time Kinematic Global Positioning System (RTK GPS) was applied to monitor bank morphology at three sites: Taole Cropland (TC), Maobula Shrubland (MS), and Maobula Cropland (MC). The measured data were analyzed using the Geographical Information System (GIS) to quantify the volume and amount of bank erosion. To verify the feasibility of other means quantifying bank erosion including remote sensing image interpretation and Bank-Stability and Toe-Erosion Model (BSTEM) simulation, their results were compared with the directly monitored results by RTK GPS. Results show that the bank erosion moduli at the TC, MS, and MC sites are 12,762, 6681 and 44,142tkm-1a-1 respectively based on RTK GPS measurements from 2011 to 2014, with the bank erosion amount varying between flood and non-flood seasons and among different years. The bank erosion quantified by remote sensing interpretation and BSTEM simulation agreed well with results from RTK GPS measurement. The main factors that influence bank erosion on the upper reaches of the Yellow River include land use in the bank area, bank height, and bank curvature. More rational land use along the Yellow River and stabilization of the river bank are required for this area. This study shows that RTK GPS monitoring is reliable and useful for bank erosion research, which has not yet been fully exploited. There is potential of applying remote sensing and model simulation to determine bank erosion of large rivers, while they should be combined and supported by field investigated data.

A network scale, intermediate complexity model for simulating channel evolution over years to decades

Excessive river erosion and sedimentation threatens critical infrastructure, degrades aquatic habitat, and impairs water quality. Tools for predicting the magnitude of erosion, sedimentation, and channel evolution processes are needed for effective mitigation and management. We present a new numerical model that simulates coupled river bed and bank erosion at the watershed scale. The model uses modified versions of Bagnold’s sediment transport equation to simulate bed erosion and aggradation, as well as a simplified Bank Stability and Toe Erosion Model (BSTEM) to simulate bank erosion processes. The model is mechanistic and intermediate complexity, accounting for the dominant channel evolution processes while limiting data requirements. We apply the model to a generic test case of channel network response following a disturbance and the results match physical understanding of channel evolution. The model was also tested on two field data sets: below Parker Dam on the lower Colorado River and the North Fork Toutle River (NFTR) which responded dramatically to the 1980 eruption of Mount St. Helens. It accurately predicts observed channel incision and bed material coarsening on the Colorado River, as well as observations for the upstream 18 km of the NFTR watershed. The model does not include algorithms for extensive lateral migration and avulsions and therefore did not perform well in the lower NFTR where the channel migrated across a wide valley bottom. REM is parsimonious and useful for simulating network scale channel change in single thread systems responding to disturbance.

Collapsing Mechanisms of the Typical Cohesive Riverbank along the Ningxia–Inner Mongolia Catchment

As one of the major sediment sources in rivers, bank collapse often occurs in the Ningxia–Inner Mongolia catchment and, to date, it caused substantial social, economic and environmental problems in both local areas and downstream locations. To provide a better understanding of this phenomenon, this study consisted of modifying the existing Bank Stability and Toe Erosion Model (BSTEM), commonly used to investigate similar phenomena, introducing new assumptions and demonstrating its applicability by comparing numerical results obtained against field data recorded at six gauging stations (Qingtongxia, Shizuishan, Bayan Gol, Sanhuhekou, Zhaojunfen, and Toudaoguai). Furthermore, the impact of multiple factors typical of flood and dry seasons on the collapse rate was investigated, and insights obtained should be taken into consideration when completing future projects of river adaptation and river restoration.

Riverbank retreat analysis of the U-Tapao River, southern Thailand

Riverbank retreat is a result of complex combinations of several processes, including subaerial processes, fluvial erosion, and bank failure. The objective of this study was to analyze riverbank retreat of six representative riverbanks along the U-Tapao River in southern Thailand using a process-based riverbank retreat model. Field and laboratory tests were conducted to determine index and engineering properties of the riverbank soil required in the modeling. In particular, the erodibility parameters of the riverbank soil were estimated using empirical formulae, measured in situ by performing a submerged jet test, and estimated from long-term bank retreat simulations using the Bank Stability and Toe Erosion Model (BSTEM) incorporated with a lumped adjustment factor. The observed bank retreat over the period from 2002 to 2016 obtained from analysis of aerial imagery was used to verify the validity of the riverbank retreat results. Good agreement with the observations was obtained from BSTEMs using adjusted erodibility parameters.

Rating of Watercourse Bank Stability Through Riparian Herbal Communities

Riparian vegetation performs an important and irreplaceable role in the countryside. The paper deals with the stabilizing effect of herbal communities on the banks of watercourse Breznický potok in geomorphological unit Kremnické vrchy (Central Slovakia). We analyzed the relationships between the vegetation coverage VEG % (%) and factor of stability (Fs) which was computed according to Bank Stability and Toe Erosion Model (BSTEM) on experimental banks. We also analyzed the relationships between VEG % (%) and BEHI (Bank Erosion Hazard Index). The value of aditional cohesion cr was calculated by RipRoot Model in BSTEM for present vegetation. The research was conducted on 20 experimental sections with 20 experimental profiles with the presented vegetation coverage (%) based on the detected percentage of grass and herbaceous on the riparian banks. The calculated results of Fs were evaluated in accordance with existing erosion damages of experimental banks which were determined in the terrain through visual classification. Research has shown a strong correlation between vegetation cover of bank VEG % and a stability factor Fs (correlation coefficient Iyx = 0.976) and between VEG % and BEHI (Iyx = 0.956). Data according to BEHI and BSTEM show similar results (Iyx = 0.912). The results were statistically tested.

Modeling sediment mobilization using a distributed hydrological model coupled with a bank stability model

AbstractIn addition to surface erosion, stream bank erosion and failure contributes significant sediment and sediment‐bound nutrients to receiving waters during high flow events. However, distributed and mechanistic simulation of stream bank sediment contribution to sediment loads in a watershed has not been achieved. Here we present a full coupling of existing distributed watershed and bank stability models and apply the resulting model to the Mad River in central Vermont. We fully coupled the Bank Stability and Toe Erosion Model (BSTEM) with the Distributed Hydrology Soil Vegetation Model (DHSVM) to allow the simulation of stream bank erosion and potential failure in a spatially explicit environment. We demonstrate the model's ability to simulate the impacts of unstable streams on sediment mobilization and transport within a watershed and discuss the model's capability to simulate watershed sediment loading under climate change. The calibrated model simulates total suspended sediment loads and reproduces variability in suspended sediment concentrations at watershed and subbasin outlets. In addition, characteristics such as land use and road‐to‐stream ratio of subbasins are shown to impact the relative proportions of sediment mobilized by overland erosion, erosion of roads, and stream bank erosion and failure in the subbasins and watershed. This coupled model will advance mechanistic simulation of suspended sediment mobilization and transport from watersheds, which will be particularly valuable for investigating the potential impacts of climate and land use changes, as well as extreme events.