Bed Level Variations Research Articles

Environmental impacts of shallow water mining in the Baltic Sea

The discovery of rare metal resources in international waters has raised seabed mining claims for large areas of the bottom. There is abundant scientific evidence of major negative consequences for the maritime environment, such as the destruction of natural landforms and the fauna that depend on them, as well as the production of enormous silt plumes that disrupt aquatic life. This study investigated the environmental risks of seabed mining for metal resources in the Baltic Sea using a combination of hydrodynamic, particle-tracking, and sediment-transport models. The models were applied for ten years i.e., 2000-2009 under prevailing conditions to simulate seabed mining operations. The focus was on sediment concentration near the seabed and its spread. The mean background concentrations were low with small seasonal bed-level variations throughout the Baltic Sea Basin. Late summer and early autumn periods were the most active. Seabed mining significantly alters the dynamics of sediment suspensions and bed level variations. The concentrations increase unsustainably to high levels, posing a serious threat to the ecological health of the Baltic Sea. The Gotland basins in the Baltic Sea are the most susceptible to mining. The bed level variations will be ten-fold, exposing the highly contaminated sediments at the seabed to the flow. In less than a year, 30-60% of the total particles released in each basin reached the thermocline layers. This study suggests that seabed mining in the Baltic Sea is not sustainable.

Sensitivity of sheltered mudflats to wind events

The impact of waves on the morphological changes of sheltered mudflats is less well studied compared to that on open flats. To investigate the sensitivity of low-energy sheltered mudflats to hydrodynamics such as waves, we carried out in situ measurements of bed level, currents, and waves on the middle flat of a sheltered mudflat in a bay in southern China. Two 1-month measurements, March 26–26 April 2021, and July 8–8 August 2021, were performed for repetition. We found that the sheltered system was not as stable as it appeared. The maximum intratidal bed-level variation, ΔZ, was <5 mm in calm conditions. However, wind speeds slightly highly than 3.0 m/s, under which significant wave height was approximately 0.1 m, triggered significant bed-level variation patterns, with ΔZ reaching up to 2 cm. Intratidal bed-level change patterns depend on the relative dominance of waves and currents: low τc (current-induced bed shear stress) and high τw (wave-induced bed shear stress) promote the generation and migration of bed ripples; comparable τc and τw, with medium-to-high values, lead to non-cyclic bed-level change patterns; high τc and high τw result in bed accumulation/degradation superimposed by bed ripple migration. From a long-term perspective, i.e. in the time scale of month to year, sheltered mudflats are stable systems, and their high sensitivity causes short-term significant bed-level variation. The sensitivity and stability of sheltered mudflats must be further investigated to explore the effects of human intervention and global climate change.

Using Noncontact Measurement of Water Surface Dynamics to Estimate River Discharge

AbstractEstimating river discharge requires simultaneous measurement of velocity and flow depth. While surface velocities are relatively easy to measure using noncontact techniques, depth measurement usually requires physically intrusive instrumentation. This limits our capability to remotely monitor discharge in natural rivers subject to bed level variations. This work tests the potential to estimate the surface velocity, the water depth, the depth average velocity, and then discharge of a river using only a sequence of images of the dynamic water surface. The method is based on a comparison between the spatiotemporal Fourier spectra of the pixel intensities of these images and the theoretical dispersion relations of turbulence‐generated surface fluctuations and gravity‐capillary waves. The method is validated through the analysis of water surface videos obtained with fixed cameras from two river sections equipped with conventional discharge gauging. The applicability of the approach is demonstrated and the measurement uncertainties are quantified. The method is affected by two main sources of uncertainty: one derives from the estimation of the velocity index and the other from the obtainable resolution of the Fourier analysis. This resolution strongly controls the observation of depth and/or velocity variations in space and in time. The technique has advantages over current approaches: it has clear physical foundations; the equipment is low cost and is highly mobile; it does not need artificial tracers or physical equipment to measure depth; and it can directly provide estimates of the key flow parameters just from time series of images of the water surface.

Morphological adjustments of the lower Orba River (NW Italy) since the mid-nineteenth century

A multi-temporal and multi-scale analysis based on historical data collection and review, maps and aerial photograph interpretation, field observations, topographic surveys, and GIS investigations was performed to (i) examine the morphological evolution of lower Orba River since the mid-nineteenth century, (ii) identify its controlling factors, and (iii) correctly interpret ongoing hydrogeomorphic conditions under a river management perspective. The riverbed experienced overall slight and non-homogeneous morphological adjustments, along with some horizontal displacements, up to the early twentieth century (Phase 0). Subsequently, two phases of channel degradation were identified. The first, from the 1920s to the 1950s (Phase 1), is characterized by slight narrowing (12.3%), the beginning of incision, and rare and little lateral migration. The second, between the 1950s and the years around 2010 (Phase 2), displays significant channel incision (mostly from the 1950s to the 1970s, from 0–1 m to 4–5 m), weak narrowing (21.0%), and only minor horizontal displacements. Over the last decade (Phase 3), widespread slight channel widening (3.4%, up to 25.7% at the reach scale) associated with the absence of a generalized bed-level variation trend was observed. The study reach has exhibited a single-thread or transitional channel since the mid-nineteenth century. Channel incision was mainly caused by extensive in-channel sediment extractions primarily carried out between the 1950s and the early 1980s at the reach and catchment scales. The long-term presence of widespread channelization works was recognized as the main reason why overall little riverbed planform adjustments occurred during the whole period investigated. The most recent dynamics were triggered by floods and were interpreted as the river response to human-induced alterations. The riverbed changes that occurred during the twentieth century match the channel adjustments commonly experienced by Italian single-thread and transitional channels as a response to various types of human disturbances. However, the detected morpho-evolutionary phases of the Orba River are only partially in agreement with those reported in the literature for other Italian rivers affected by similar anthropogenic pressures, as some differences exist in timing and magnitude of prevalent channel adjustments. An overall slight potential for channel recovery, priorities for rehabilitation, and the main objectives for the next-decades management were identified. This research provides insights into the medium- and short-term morphological evolution of Italian rivers, and its outcomes represent an essential piece to drive river management towards sustainable and effective river restoration and risk mitigation measures framed within a larger, multidisciplinary, and objective-based context. A wide spectrum of both consolidated and newly developed GIS-based planform metrics was considered to assess the channel morphological evolution in detail, providing an operative reference framework for future investigations.

Observations of Tidal Flat Sedimentation within a Native and an Exotic Spartina Species

Field measurements of bed elevation and related wave events were performed within a tidal marsh, on two cordgrass species, Spartina anglica (exotic) and Spartina maritima (native), in the Bay of Arcachon (SW France). Bed- and water-level time series were used to infer on the sediment behavior patterns from short to long term. A consistent response was found between the bed-level variation and the wave forcing, with erosion occurring during storms and accretion during low energy periods. Such behavior was observed within the two species, but the magnitude of bed-level variation was higher within the native than the exotic Spartina. These differences, in the order of millimeters, were explained by the opposite allocation of biomass of the two species. On the long term, the sedimentation/erosion patterns were dominated by episodic storm events. A general sediment deficit was observed on the site, suggested by an overall bed-level decrease registered within both species. However, further verification of within species variation needs to be considered when drawing conclusions. Despite possible qualitative limitations of the experimental design, due to single point survey, this work provides original and considerable field data to the understanding the different species ability to influence bed sediment stabilization and their potential to build marsh from the mudflat pioneer stage. Such information is valuable for coastal management in the context of global change.

Key morphological changes and their linkages with stream power and land-use changes in the Upper Tapi River basin, India

Knowledge on spatio-temporal variations in planform, hydraulic geometry, and bed-level variations of alluvial streams is required for planning and development of hydraulic structures and bank protection works. In the current study, a Geographic Information System (GIS) has been used to analyze topographical maps, multi-temporal remotely sensed imagery, and hydrologic and hydraulic data to extract the morphological parameters of the Upper Tapi River, India. The river has been found to have consistent migration towards the northern direction, with erosion/deposition on right/left banks. The river has not experienced any major meander except in the lower reaches of the Upper Tapi Gorge and minor braiding conditions at the location where the river emerges from mountainous topography to the plain region. The analyzed river cross sections were found to be depth dominated, and contain large flows within the channel banks. The cross-sections exhibited moderate channel bed adjustments in 1994, 2006, and 2007 wherein excessive sediment flux and stream power were capable of causing morphological changes in the river. High intensity rainfall in the subcatchment resulted in high sediment flux into the river during 1994, which was reported to cause significant aggradation at the downgauging station. The analysis of sediment flux into the river in conjunction with decadal land use land cover, revealed that sediment yield from the catchment was reduced during 2000–2010 due to an increase in water bodies in the form of minor hydraulic structures. The entry of comparatively less sediment laden water into the river, resulted in moderate bed degradation especially in 2006 and 2007 as observed at the downstream station. The methodology applied in the current study is generic in nature and can be applied to other rivers to identify their morphological issues.

Multiple Environmental Variables Affect Germination and Mortality of an Annual Salt Marsh Pioneer: Salicornia procumbens

Salt marshes, providing numerous ecosystem services, are degrading worldwide. To effectively aid conservation and restoration efforts, increased knowledge on marsh expansion processes and the initial establishment of pioneer vegetation is essential. In this study, we disentangle environmental drivers that affect the lifecycle of the annual pioneer Salicornia procumbens at the salt marsh edge. We studied the effect of various environmental variables on the start of germination, germination success and mortality before seed-set in a field experiment in the Dutch Wadden Sea at Westhoek. Our results indicate that temperature and sedimentation inhibited the initiation of germination. Once germination occurred, higher precipitation rates increased germination success. In contrast, sedimentation rates above 0.5 mm day−1 halved germination success through burial of freshly sprouted seedlings. Unexpectedly, natural germination was low, indicating that seed availability may have been limited, despite a seed source nearby. Frequent inundation, extended periods without inundation (through desiccation of the soil) and a highly dynamic bed level increased mortality before seed-set. Consequently, bed-level dynamics (erosion, sedimentation and bed-level variation) impact seed production dually (decrease germination and increase mortality) and thus potentially reproduction success. A high seed reproduction is crucial for annuals, such as S. procumbens, to re-establish the following year. Next to advancing our general knowledge of natural salt marsh expansion, results in this study can also be used to assess the potential of a given site for salt marsh stimulation or restoration. Seed availability and local bed-level dynamics are key in the successful establishment of a salt marsh pioneer: Salicornia procumbens.

Bed level variations around submerged tandem bridge piers in sand beds

ABSTRACT The characteristics of scour hole around the submerged tandem pier in alluvial bed plays an important role in analyzing the problem of parallel bridge failures. The present study investigates the scour hole properties around single and tandem pier arrangements with spacing 2d (d, diameter of pier) under varying flow conditions. Experiments were carried out on a mobile bed channel having mean sediment size 0.75 mm and geometric standard deviation (σg ) of 1.27. The cylindrical piers of diameter 4.5 cm are vertically embedded in the mobile channel bed having flow depth of 15 cm with a flow range of 0.02–0.035 m3/s in clear water conditions (U0/Uc = 0.45–0.79). The scour depth around the rear pier is 30% less than the front pier in tandem case for all the flow conditions. Further, with increments of 0.005 m3/s discharge, 20–30% more scour depths are observed around the piers (single and front pier of tandem). In all, 40% more sediment erosion is observed around the piers in tandem case vis-à-vis single pier case. The study reveals that parallel bridge piers are more prone to local scour/erosion than single pier in alluvial beds for similar flow conditions.

A model for simulation of debris flow sedimentation in slit detention-dam reservoirs

Debris flow is a natural phenomenon that requires appropriate structural measures such as detention dams to reduce hazards resulting from it. The objective of this paper is to present a two-dimensional numerical model to investigate debris flow deposition in the reservoir of the detention slit dams. The governing equations include shallow water equations considering the bed level variation, sediment continuity, and debris-flow transport equations. Shallow water equations were discretized using the MacCormack scheme and then Banihabib Scheme was applied for solving sediment continuity equation. The governing equations were solved in an iterative procedure and as a result, flow properties and bed level variations were obtained in silt dam reservoir. The model performance was evaluated against experimental and numerical models in two aspects including the outflow hydrograph and reservoir bed level variations or trapping efficiency. The model performed quite well in outflow hydrograph simulation, and the comparison of the bed level variations or trapping efficiency illustrated that the simulated values were acceptable. A sensitivity analysis of the parameters was carried out to analyze the influence of parameters variation on outflow and sedimentation volume. The results of this sensitivity analysis revealed sedimentation is more sensitive to the parameter variation than outflow hydrograph. Generally, the proposed numerical method can provide insights on the debris flow deposition in slit dam reservoir, which could be useful for slit dam design.

The heterogeneity of mudflat erodibility

The prediction of the erosion of mudflats is hampered by inaccurate estimates of the erodibility distribution of the sediment bed. To investigate how erodibility varies in space and what the vertical distribution over the sediment depth is, comprehensive observations of the sediment properties, hydrodynamics and bed-level changes were conducted on an intertidal flat in the Western Scheldt Estuary, the Netherlands. The erosion potential on a mudflat is determined by the critical shear stress for erosion (τe), erosion rate coefficient (M) and local hydrodynamic conditions. A clear difference in hydrodynamic forcing was observed, leading to significant bed level variations at the low water line, where erosion often occurs during very shallow water condition, and a nearly constant bed level at the upper part. The erosion parameters τe and M could be determined over a sediment bed of 12 cm at the low water line. The erosion coefficient M can be considered constant with depth, although there is a large spreading. A clear vertical variation of τe was found: τe increased significantly downward from 0.10 Pa at the sediment surface to 1.13 Pa at 12 cm below the surface. Additionally, there was a strong indication that the presence of diatoms enhanced τe in the upper 2 mm of sediment by five times of the abiotic τe (from 0.09 Pa to 0.46 Pa). These findings lead to the following improvement for predicting morphological changes of tidal mudflats: (1) very shallow conditions should be better simulated, (2) the vertical distribution of τe should be considered. Otherwise, erosion rates can be overestimated, especially during extreme events, because exposure of the deeper well-consolidated layer likely occurs; and (3) an appropriate description of the effect of diatoms should be considered as part of the bottom boundary condition.

Numerical and Experimental Studies in Prediction of Bed Levels of Aggrading Channels

A semi-coupled 1D numerical model is presented to compute transient bed and water levels of aggrading channels due to the overloading of sediments. The numerical model solves mass and momentum equations (i.e. de Saint–Venant equations) for water and continuity equations for sediments simultaneously, using explicit finite difference scheme while considering upstream and downstream boundary conditions in the channel. Series of experimental studies are reported for measurements of bed and water levels in an aggrading channel due to the overloading of uniform sediments, in a flume installed at the Advanced Hydraulics Laboratory of SVNIT. The performance of bed level variation models, with different sediment transport functions, has been validated using the laboratory measurements. The performance of the numerical model is dependent on sediment transport functions. In addition, the performance of the proposed numerical model has been verified with existing numerical models on prediction of bed level variations. The proposed numerical model with recommended sediment transport function has been found to perform better than the existing numerical models on bed level variations of uniform sediment beds.

Prediction of bed level variations in nonuniform sediment bed channel

In the present study, a numerical model, based on one-dimensional de Saint-Venant equations along with sediment continuity equation, is developed for prediction of bed levels in non-cohesive sediments in aggrading alluvial channels. One-dimensional, unsteady flow equations and sediment continuity equations are solved using ‘shock-capturing’, second order accurate, explicit MacCormack finite difference scheme while considering upstream and downstream boundary conditions in the channel. Series of experimental investigations have been undertaken for measurements of bed and water levels in an aggrading channel due to overloading of nonuniform sediments, extracted from the bed of Tapi River at Surat City, in a flume installed in Advanced Hydraulics Laboratory of SVNIT, Surat, India. A satisfactory coupling between the water flow and sediment flow has been achieved. The sediment continuity equation is used for the each size class to compute the volume of each size class after each time step at any computational node in the computational grid. The fractional bed and suspended load transport capacities for different size fractions have been computed using fractional transport laws for nonuniform sediments. The active bed layer concept has been implemented in finite difference scheme to consider the interaction and exchange of sediment and water flow near the mixing layer. The performance of developed numerical model has been satisfactorily verified with independent experimental data of nonuniform sediment bed. Also, consideration of sediment nonuniformity in computation of bed level variation has been demonstrated by comparing the results based on sediment transport functions of uniform and nonuniform sediments.

Temporal and spatial morphological variations along a cross-shore intertidal profile, Jiangsu, China

Fifteen monthly field surveys were conducted from September 2012 to November 2013 at ten representative stations along a cross-shore profile, covering the entire tidal flat. Results indicate that tidal currents significantly affect bed level variations over bare flats, while subsurface processes (e.g., soil subsidence and expansion) are likely to play an important role in changing the bed level of the upper intertidal flat where salt marshes are present. The cross-shore profile shows a clear double-convex shape, and different geomorphic zones display distinctive variation. Above the mean high water level (MHWL), the bed level is generally stable. The region around the MHWL, where the upper convex point is present, is a location of high sedimentation due to the weaker hydrodynamic conditions and the settling and scour lag effects, it keeps growing with the increase of inundation frequency. A concave point occurs in the middle part of the intertidal flat, showing considerable erosion. Near the mean low water level (MLWL), the lower convex point is elevated due to the long-shore tidal current and associated sediment transport (the flood dominated transport during summer exceeds the ebb dominated transport during winter, hence the net effect favors sedimentation). Further seawards, the area below the MLWL is strongly eroded. The cross-shore profile follows a “stable-accretional-erosional-accretional-erosional” sequence. Overall, the measurements indicate that the interplay among vegetation, hydrodynamics and sediment transport is critical in shaping the cross-shore morphology of the intertidal flats along the Jiangsu coast of China.

Probabilistic failure analysis of riprap as riverbank protection under flood uncertainties

Existing riverbank riprap could face the risk of failure if the flood regime changes in future. Additionally, changed sediment transport in rivers, as a possible result of climate change, impacts the failure risk of flood protection measures. Evaluation of this potential failure is the primary issue of riprap stability and safety assessment. The consequences of the bank failure are probably uncontrolled erosion and flooding with disastrous consequences in residential areas or damage to infrastructures. Thus, a probabilistic analysis of riprap failure considering different mechanisms due to the flood and sediment transport uncertainties is required to assess embankment stability. In this article, the concept of a probabilistic assessment model based on Monte Carlo simulation method, moment analysis methods, and Rosenblueth point estimation method are presented to define the failure risk of riprap as the river bank protection. The probability of failure in different modes, namely direct block erosion, toe scouring and overtopping, has been defined by taking into account the river bed level variation based on bedload transport described with a probabilistic function of the peak discharge. The result of three models comparison revealed a good agreement (the average deviation of less than 2%) in estimation of riprap failure probability. This model is a strategical tool to search the critical river reaches and helps to evaluate the risk maps. So that, the model could cover the engineering aspect of environmental stability in the rivers with riprap as the bank protections.

Application of the Mike21C model to simulate flow in the lower Mekong river basin.

Numerical models are useful tools that play an important role in many research projects. Mike21C is one of the most well-established models for simulating a variety of processes, including bank erosion, bed level variations, aggradation, and degradation. Such processes are caused by a variety of activities, such as construction and dredging, as well as seasonal flow fluctuations. Mike21C based on an orthogonal curvilinear grid, which enables a computational speed that is faster than that of other grids. The hydrodynamic part of the model is based on solving the Saint-Venant equations. In this research, the Mike21C model was applied to simulate water depth, flow discharge distribution, and suspended transport rate along reaches of the Bassac River the on Vietnam. The data files of the curvilinear grid and bathymetry were used to generate the model. A time series for the discharge and water level of hydrological stations was established. The model was calibrated using the water level and suspended load data collected during high and low flow discharges. The simulation results show that the model can be applied well to other areas.

Numerical Simulation of Bed Level Variation in Open Channels Under Steady Flow Conditions

Bed load transport is an important process in maintaining balance and stabilising channel geometry for restoring the form and function of river ecosystems. The amount and spatial distribution of bed load sediment particles contribute significantly to riverbed level changes. The prediction of bed load sediment transport evolution is an important aspect of catchment planning. This work can be effectively supported through numerical simulation by detailed analyses of flow components and sediment transport inside watersheds. The purpose of this research is to develop a twodimensional depth-averaged numerical model for flow and sediment transport using eight bed load transport equations to predict the time variation of bed deformation in steep slope, torrents and mountain river areas. The two-dimensional depth-averaged shallow water equations, along with the sediment continuity equation, are solved by using the Marker and Cell explicit scheme. Applying the eight bed load transport formulas to both ADM and MLSHM experimental flumes. After we will choice to the most appropriate formula to simulate the bed load transport rate and bed elevation change in the Yang yang mountains river in South Korea. The differences found between the measured experimental data and the numerical simulation for both flow and the time variations of bed deformation showed that the numerical model used in this research is useful for the analysis and prediction of riverbed level variations.

Wireless monitoring of scour and re-deposited sediment evolution at bridge foundations based on soil electromagnetic properties

Hydraulic structures constitute the most vulnerable elements of transportation infrastructure. Recent increases in precipitation have resulted in severe and more frequent flash flooding incidents. This has put bridges over waterways at higher risk of failure due to scour. This study presents a new sensor for measuring scour depth variation and sediment deposition processes in the vicinity of the foundations to underpin systems for early warning of impending structural failure. The monitoring system consists of a probe with integrated electromagnetic sensors designed to detect changes in the dielectric permittivity of the surrounding bridge foundation. The probe is equipped with a wireless interface and was evaluated to assess its ability to detect scour and sediment deposition in various soil types and under temperature and water salinity conditions that would commonly occur in a practical installation environment. A novel methodology is also developed enabling discrimination between in situ and re-deposited sediment delivering vital information about the load bearing capacity of the foundation. The experimental approach was validated using ‘static’ scour simulations and real-time open channel flume experiments. Results indicate that the sensor is highly sensitive to underwater bed level variations and can provide an economical and accurate structural health monitoring alternative to existing instruments.

LARGE SCALE EXPERIMENTS ON BEACH EVOLUTION INDUCED BY BICHROMATIC WAVE GROUPS WITH VARYING GROUP PERIOD

New large scale experimental data have been presented showing the wave group influence on beach morphodynamics at the surf and swash zones. Bichromatic wave conditions were generated varying the modulation bandwidth but keeping the wave energetic content constant within the experimentation limits. The wave group influence in the surf zone is observed in the form of the cross-shore location of the breaker bar respect to the initial still water level (SWL) location, which has been shown to increase as increases the wave group period. This influence is explained in terms of differences on the surf zone width induced by the varying wave group periods. In the swash zone, time dependent bed level elevation measurements were done using a newly developed conductivity technique, the CCM+ system. Bed level time variations at the swash zone have shown to be composed of a long scale trend and bed level oscillations of shorter frequencies related to the wave group forcing. A good spectral correlation has been found between the water surface elevation and bed level variation at the wave group period for every bichromatic component indicating an important influence of wave groups on the swash zone morphodynamics.

Vertical distribution of Skewness and asymmetry in a boundary layer on a mobile bed. Experiment andk-ωmodel comparison

As the waves approach the coast, non-linearities become increasingly stronger. The interactions between the waves and loose bottoms then generate complex features within the turbulent boundary layer, which are difficult to measure and model. Experiments involving non-linear wave propagation over a mobile bed with detailed boundary layer velocity measurements and bottom elevations are presented. These data suggest a transformation in velocity time series as they are measured closer to the bed within the boundary layer with an increase in velocity skewness and a reduction in asymmetry. Additionally the vertical diffusion of momentum within the boundary layer is shown to be one order of magnitude larger than that over fixed beds. A k-ω model accounting for the measured bed level variations is used to mimic the flow in the boundary layer. In this work we present a strategy to combine bottom level variations with a k-ω model and show that it is possible to reproduce the observed experimental results. The bed vertical mobility is shown to be largely responsible for additional vertical diffusion of momentum within the boundary layer.

Numerical assessment of bathymetric changes caused by the 2004 Indian Ocean tsunami at Kirinda Fishery Harbor, Sri Lanka

Thus far various numerical models have been developed and improved to aid understanding of the sediment transport process due to tsunamis. However, the applicability of these models for the field-scale bathymetric change remains a major issue due to the scarcity of measured bathymetric data immediately before and after tsunamis. This study focuses on assessing the applicability of the sediment transport model by comparing the model results with measured bathymetry data obtained one month before and two months after the 2004 Indian Ocean tsunami at Kirinda Fishery Harbor, Sri Lanka. Obtained model results were compared with measured data along four different transects. In particular, similar to the measured data, the model reproduced the bed level change at the harbor mouth well, although it shows some discrepancy on bathymetric change along the shoreline, which is directly affected by littoral drift. Therefore, it is noted that the divergence of reproducing the local bathymetry change is due to the normal wind wave effect on measured data and the model limitations. Hence we included the wind wave effect in modeled data and the discrepancy between measured and modeled data was reduced. Furthermore, the modeled bed level change indicates a dynamic behavior in terms of the net variation during the tsunami flow, such that deposition dominates in the inflow and erosion dominates in the backflow. Both bed level variation and the suspended load concentration reveal that the large amount of eroded sediment attributable to tsunami waves was in suspended form and was deposited in the nearshore area after the water fluctuation had abated. The model results further indicate that eroded sediment at the initial depth deeper than 11m might be brought by the incoming tsunami waves and deposited in the nearshore area where the depth is shallower than 7m.