Suspended Sediment Transport Rate Research Articles

Interactions between Hydrodynamic Forcing, Suspended Sediment Transport, and Morphology in a Microtidal Intermediate-Dissipative Beach

This study aims to investigate the hydrodynamic-morphological interactions on a microtidal intermediate-dissipative beach under low to moderate wave energy conditions using field measurements during two climatic seasons. The separate contributions of currents, sea-swell waves, and infragravity waves to high- and low-frequency sediment fluxes were analyzed. The infragravity wave energy was more relevant near the swash zone than in other areas. Although the currents are the primary suspended sediment transport mechanism, the results suggest that the waves are an important driver of sediment suspension from the seabed. The results indicate that Sea-Swell (SS) waves and cross-shore currents are the prevailing hydrodynamic factors in nearshore sediment transport, and the cross-shore suspended sediment transport rates are higher than those in alongshore transport. The submerged bar intensified during the wet season (1–4 November 2018) when the wave height intensities were lower, contrary to the dry season (24–25 March 2018). Significant accretion nearshore was identified (in the subaerial beach) during the wet season when the suspended sediments were greater, the SS-wave heights nearshore were lower, and sediment flux was directed onshore. A notorious erosion was distinguished during the dry season. The most representative volume changes occurred during the dry season (with high erosion), which is attributed to the high SS-wave energy.

Interactions between Hydrodynamic Forcing, Suspended Sediment Transport, and Morphology in a Microtidal Intermediate-Dissipative Beach

This study aims to investigate the hydrodynamic-morphological interactions on a microtidal intermediate-dissipative beach under low to moderate wave energy conditions using field measurements during two climatic seasons. The separate contributions of currents, sea-swell waves, and infragravity waves to high- and low-frequency sediment fluxes were analyzed. The infragravity wave energy was more relevant near the swash zone than in other areas. Although the currents are the primary suspended sediment transport mechanism, the results suggest that the waves are an important driver of sediment suspension from the seabed. The results indicate that Sea-Swell (SS) waves and cross-shore currents are the prevailing hydrodynamic factors in nearshore sediment transport, and the cross-shore suspended sediment transport rates are higher than those in alongshore transport. The submerged bar intensified during the wet season (1–4 November 2018) when the wave height intensities were lower, contrary to the dry season (24–25 March 2018). Significant accretion nearshore was identified (in the subaerial beach) during the wet season when the suspended sediments were greater, the SS-wave heights nearshore were lower, and sediment flux was directed onshore. A notorious erosion was distinguished during the dry season. The most representative volume changes occurred during the dry season (with high erosion), which is attributed to the high SS-wave energy.

Gravity‐Driven Differences in Fluvial Sediment Transport on Mars and Earth

AbstractThere is abundant evidence from fluvial landforms and deposits that Mars had rivers that actively transported sediment and shaped its surface. Sediment transport equations are playing a key role in quantifying river processes from these observations, which continue to increase in quality and quantity. In this study, we review sediment transport equations developed on Earth and isolate the effect of gravity for the case of an alluvial channel. We compare 33 formulas used to calculate the sediment transport rate, under transport‐limited conditions, for grain sizes that range from silt to boulders and a lognormal sediment distribution. Results indicate that for a given discharge, channel morphology and grain size, the lower gravity on Mars compared to Earth results in: (a) larger grains mobilized on Mars and transported in suspension, and (b) larger suspended sediment transport rates on Mars and therefore larger total transport rates. Importantly, the effect of gravity is different for bed load and suspended load, with nonlinearity at the bed load‐suspended load transition zone. Therefore, typical total‐load transport relations that do not distinguish between bedload and suspended load are not appropriate for other planets as they simplify the effect of gravity. Gravity‐driven differences in fluvial sediment transport should produce differences in sediment sorting, morphology and stratigraphy between Earth and Mars. Additionally, our results show how Earth‐derived fluvial sediment transport theory can be applied beyond Mars to other planets and moons.

Changes in Water and Sediment Processes in the Yellow River and Their Responses to Ecological Protection during the Last Six Decades

The variation of river hydrologic process can reflect the impact of not only natural factors, but also human activities. The purpose of this study is to reveal the change in the hydrologic regime of the Yellow River and its response to ecological protection. Based on the daily water and sediment observation data of representative gauging stations of the Yellow River, we analyzed the variation of the annual and monthly runoff and suspended sediment load (SSL), as well as monthly mean runoff, suspended sediment transport rate (SSTR), sediment inflow coefficient, and hydrological regime in a decadal average of the gauging stations during the period of 1960–2019. The results showed that the variation of annual runoff and SSL, as well as the monthly mean runoff and SSTR in a decadal average, had a significant decreasing trend in the 1960s–1990s, which was mainly in response to the gradual implementation of ecological protection measures such as afforestation, terrace construction, check dam construction, etc., in the basin. In 2000s and 2010s, the annual runoff increased, while the SSL increased slightly. This was a response to the implementation of new river management measures such as ensuring the ecological water demand of the lower reaches and scouring the riverbed by manually regulated water discharged from the Xiaolangdi Reservoir. At the same time, the monthly mean runoff and SSTR for the flood season (July–October) decreased remarkably while the process curve of the monthly mean discharge and sediment concentration changed from a clockwise loop to a counterclockwise loop in the river reach below the Xiaolangdi dam. This was a comprehensive response to the environmental protection measures in the Yellow River basin, in which the construction and operation of the Xiaolangdi Reservoir played a key role. This study can provide reference for river basin management.

Suspended-sediment transport related to ice-cover conditions during cold and warm winters, Toudaoguai stretch of the Yellow River, Inner Mongolia, China

The presence of winter ice in cold regions changes the water level, flow rate, velocity distribution, and other parameters of the river, which in turn affects the sediment concentration and channel evolution. Based on data obtained from Toudaoguai Hydrological Station from 1959 to 2021, this study examines the characteristics of the ice regime during cold and warm winters and the water and sediment transport processes along the Yellow River in Inner Mongolia in the context of climate change. The Mann–Kendall test and trend analysis were applied to define the years of temperature mutations and their trends, and the temperature mutation point was determined to be the 1987/1988 season. The study considers the effect of climate change on the combination of hydrological and hydraulic conditions. Therefore, trends in suspended sediment transport, ice type formation, water discharge, and storage in different ice flood seasons (November 1 to March 31, from 1998 to 2021) were attained. Based on the cumulative negative air temperature, winters were categorized into three types, warm, normal, and cold (52.2%, 17.4%, and 30.4%, respectively). Strong and weak grades further divide cold and warm winters, and statistical analyses were used to examine the characteristics of ice, water discharge, channel storage, and sediment transport. The duration of open water, freeze-up, ice cover, and breakup periods were calculated, and the relationship between the suspended sediment transport rate and discharge rate in these various ice periods was defined. The obtained relations show that the suspended sediment rate during the ice cover and first drift was smaller than that during the open water and post-breakup conditions. For the ice cover period, the sediment transport rate was on average approximately four times smaller than the freeze-up condition and six times smaller than the open water condition. The reduced sediment transport rate in the freeze-up period can be attributed to the weakened vertical turbulent mixing and increased flow resistance.

A new method for measurement and calculation of unit width suspended sediment transport rate

Abstract The unit width suspended sediment transport rate is the basis for calculating river sediment flux, which provides an important measure of river hydrology and morpho-dynamics. By integrating the vertical distribution of the suspended sediment concentration and logarithmic flow velocity, the formula for unit width suspended sediment transport rate is presented. Based on this formula, the calculation of the near-bed relative transport rate missing in field measurement is given. Moreover, a new stratified water sampling device is invented for suspended sediment transport rate measurement by the six-point method at Mengsheng hydrological station in the Lancang River basin. Results of 24 sets of measurements show that the near-bed relative sediment transport rate ranges from 3.4 to 10.7% and is significantly positively correlated with the suspension index. The unit width suspended sediment transport rate measured by the traditional depth integrating method is on average 15.0% smaller than that calculated by the theoretical formula, which can be a reference for correcting the sediment transport rate based on the traditional method. This work provides a new device and a new method for the measurement and calculation of the unit width transport rate of suspended sediment, which has theoretical and practical significance.

In situ observations of hydro-sediment dynamics on the abandoned Diaokou lobe of the Yellow River Delta: Erosion mechanism and rate

In situ observations of suspended sediment concentrations (SSCs), bed elevations, and concurrent hydrodynamics were conducted with an instrumented tripod on an abandoned lobe of the Yellow River Delta in the winter of 2014–2015. Four typical winter storms were recorded, but no significant local seabed erosion was observed at the observation site. Nevertheless, the sediment dynamic processes in this area were inferred from the data. The bottom sediment is eroded by the waves induced by strong northerly winds, and the erosion source area is located northwest of the observation point. Therefore, during strong wind and wave conditions, the observation point forms a horizontal SSC gradient, which generally decreases from west of to east of the observation point. The gradient mainly passes the observation site through diurnal tidal horizontal advection and is intermittently influenced by advection by the residual current driven by sea‒land wind and semidiurnal tides. Additionally, local resuspension of a “fluffy layer” on the seabed by the semidiurnal tide occurs. Flood tides transport the SSC gradient southeasterly, while ebb tides push the gradient back periodically. An asymmetry in the suspended sediment transport rate exists and is estimated to be 1.77 kg m−2 s−1 to the southeast. A new parameter, the net loss rate of suspended sediment, is defined and is estimated to be 0.0109 g L−1 h−1. These findings provide a better understanding of the erosion mechanism of the Diaokou lobe and some new ideas/methods for analysing hydrodynamics and sediment dynamics with a single-point measured dataset.

Theoretical model of suspended sediment transport capacity in submerged vegetation flow

Quantifying suspended sediment transport capacity (SSTC) in submerged vegetation flow is vital to predicting the topographical changes of a river channel with vegetation and the effect of ecological restoration projects. Based on the definition of suspended sediment transport rate (SSTR) and the assumption that the energy maintaining sediment suspension (suspension work) comes from the turbulence kinetic energy (TKE) of flow, two models for estimating SSTC in submerged vegetation flow were proposed in this study. The SSTR-based model calculated SSTR by taking the depth-integral average of the product of local velocity and suspended sediment concentration and dividing it by discharge per unit width. The Energy-based model introduced suspension work to the double-averaging TKE budget equation as a sink term. That is to say, the production of TKE is used for sediment suspension and viscous dissipation. In the open channel without vegetation, a fixed proportion of the TKE production term is used to maintain the sediment suspension, but the proportion falls and is no longer a constant for the reason that the presence of submerged vegetation raises the viscous dissipation term. To represent this influence, an equivalent ratio coefficient was introduced. Thus, the SSTC model was derived. Then, a series of experiments in suspension capacity flow through submerged vegetation were carried out to verify the two models. Results showed that the two models could estimate the SSTC in flow with submerged vegetation well. Moreover, it was found that the suspended sediment is mostly transported by the water flow above the vegetation layer, and the proportion of which rises as discharge and vegetation density increase. Furthermore, compared with the bared-bed channel, the increase of TKE dissipation term in submerged vegetation flow leads to the decrease of SSTC, which is why submerged vegetation promotes sediment deposition.

Roles of advection and sediment resuspension-settling in the turbidity maximum zone of the Changjiang Estuary, China

Understanding mechanisms of suspended sediment transport in estuaries is critical for predicting estuarine geomorphic evolution, managing navigation and fisheries, and monitoring the health of estuarine ecosystems. Yet monitoring suspended sediment transport in estuaries is challenging due to the influences of both riverine and marine processes, and traditional in situ observations cannot directly differentiate contributions of multiple physical processes (e.g., advection and resuspension/settling). Here we investigated the effects of advection and sediment resuspension/settling on suspended sediment transport within the turbidity maximum zone at the South Passage of the Changjiang Estuary. The Changjiang catchment is notable for its long history of intensive human activities including dam construction, which has caused significant geomorphic changes along the river and its estuary. We conducted synchronized hydrodynamic measurements at three monitoring stations along the river channel and imported time series of current velocity and suspended sediment concentration (SSC) at these stations into a simplified, one-dimensional box model to separate in situ SSC into advection- and resuspension/settling-induced components. Our results show that high SSC consisted of a background SSC of 0.93 kg m−3 maintained by advection that contributes to 97.9% of the total average SSC, and a fluctuating SSC controlled by sediment resuspension and settling. The background SSC was higher than the fluctuating SSC at all times, indicating that sediment advection was stronger than local sediment resuspension in the river channel. We compared time series of SSC components, bed-level change and suspended sediment transport rates in the South Passage with previous observations in the nearby subaqueous delta, and found that the South Passage of the Changjiang Estuary experienced net accretion during summer because of the relatively high background SSC maintained by advection of fluvial sediment. In contrast, the subaqueous delta experienced erosion due to strong local sediment resuspension and weak sediment delivery by advection. Our results highlight the spatial variability in the magnitudes of sediment advection and resuspension/settling as key drivers of geomorphic changes of deltas and estuarine channels in response to sediment reduction caused by upstream dam construction.

Indirect Estimation of Flow and Suspended-sediment Concentration and Load in Small Mountain Streams: an Exploratory Study in Ribeira Seca Stream, Madeira Island

The aim of this study was to assess the applicability of indirect techniques for streamflow and suspended sediment concentration estimation and their use in the calculation of suspended sediment transport rate in the small mountain watersheds of Madeira Island, Portugal. Emphasis was given to the application of salt dilution gauging to the indirect determination of the flow rate and the use of water turbidity data to estimate the concentration of suspended sediments. The field and laboratory work carried out are briefly described, and the main experimental results and the field data from the short measurement campaign performed in the Ribeira Seca stream in Faial, on the north side of the island, are presented and discussed. Whilst the measurement campaign carried out was temporally and spatially limited, it was pioneering for Madeira and allowed to verify the applicability of the indirect hydrometric and sedimentometric techniques used in this exploratory study.

Suspended sediment transport map for disaster mitigation in the upper course of Jangkok River

Jangkok River, a very important river for irrigation purposes in Lombok Island Indonesia is experiencing a rapid change in the land use of its watershed. The conversion of trees into seasonal crops in the watershed causes a decrease in the carrying capacity of the watershed and reduces its ability to prevent soil erosion. Environmental damages such as erosion and sedimentation along the river are becoming increasingly difficult to control. This paper proposed an idea to identify river conditions based on suspended sediment concentration. A series of field measurements of suspended sediment concentrations and river flow discharges were carried out to obtain the relationship between these two parameters. A resulting watershed map contains information on the rate of suspended sediment transport in the form of a suspended sediment-flow discharge rating curve is designed as a sediment conservation health indicator of the watershed. The map allows the authority to observe the condition of each river order in the upper course of the Jangkok River since the nearby tributaries are most likely to have their pattern of suspended sediment transport rate. The finding from this preliminary study can facilitate the drafting and implementation of the right policy in watershed conservation management planning which leads to preventive action and better preparedness in disaster mitigation.

Importance of infragravity waves in a wave-dominated inlet under storm conditions

The processes associated with infragravity waves (IGW) and their role on the hydro-sedimentary dynamics of a wave-dominated inlet are investigated using field observations collected at the Albufeira Lagoon (Portugal) during storm Leslie in October 2018. During the storm, significant IGW heights reached up to 1.0 m in the surf zone and 0.4 m inside the lagoon. IGW frequencies were blocked by ebb currents at the flood-delta and this effect was stronger for higher IGW frequencies. Therefore, low-frequency IGW were able to propagate further into the inner lagoon. The application of a 1D energy balance equation suggests that depth-induced breaking and bottom friction contributed equally to dissipate IGW energy at the flood-delta and that this dissipation was stronger during the flood than during the ebb.Large horizontal velocities under IGW crests increased the instantaneous suspended sediment transport rate by up to two orders of magnitude during flood at the flood-delta. The net suspended sediment transport rate and its variability, associated with the wave motion, was positive (landward) during flood and negligible during ebb. These positive values were associated with large wave-induced orbital velocities, suggesting that waves were more effective than tidal currents in inducing suspended sediment transport. The oscillatory suspended sediment transport rate was directed towards the lagoon and dominated by IGW frequencies. The observed sediment accretion of the northern channel occurred during the most energetic IGW. The measurements presented in this study and their analyses demonstrate how IGW play a major role in the sedimentary dynamics of wave-dominated inlets during storm conditions.

EFFECT OF NET CROSS-SHORE SAND TRANSPORT ON BEACH PROFILES

The concept of an equilibrium beach profile is convenient and widely adopted for long-term simulations of shoreline changes and beach profile evolutions. The equilibrium profile is regarded as a profile with net cross-shore sediment transport rate qn = 0. Kobayashi et al. (2008) proposed formulas for offshore suspended sediment transport rate qs and onshore bedload transport rate qb and derived the equilibrium profile equation of Dean (1991) for the case of qn = (qs+ qb) = 0. Their model is extended to equilibrium profiles with net offshore (qn0) sediment transport rates. The equilibrium profile with qn=0 is modified by periodic beach nourishment (qn0). The extended model predicts the degree and location of profile modifications as a function of qn and it can be used to improve beach nourishment design and devise barrier beach overwash countermeasures.

Field Observations of Turbulence, Sand Suspension, and Cross‐Shore Transport Under Spilling and Plunging Breakers

AbstractMeasurements of wave orbital velocity, near‐bed turbulence levels, and sediment suspension were obtained under plunging and spilling breakers in the outer surf zone on the beach at Vejers, Denmark. For the same range of relative wave heights and indicators of wave nonlinearity, we observed significantly larger suspended sediment concentrations and onshore‐directed rates of suspended sediment transport under (long period) plunging breakers, compared to (short period) spilling breakers. This is consistent with the long‐held understanding that, for a given beach slope, onshore transport and beach accretion are associated with longer‐period waves and offshore transport and erosion are associated with shorter‐period waves. An intra‐wave analysis of hydrodynamics and sediment suspension revealed that the main reason for the larger suspended sediment transport rates under plunging waves was (i) larger time‐averaged suspended sediment loads under plunging waves, and (ii) a larger difference in cumulated sediment load under the wave crest phase compared to the wave trough phase for plunging breakers. This latter difference was due to an earlier arrival at the seabed of higher levels of turbulent kinetic energy under plunging waves compared to spilling waves. Hence, both magnitude and timing within the wave cycle of turbulent kinetic energy production are important in a quantification of sediment transport under breaking waves. For ensemble‐averaged intense suspension events, contributing roughly 50% of the total sediment suspension during individual records, we found that instantaneous near‐bed sediment load was linearly related to instantaneous levels of Froude‐scaled turbulent kinetic energy.

Seasonal sediment dynamics on the Barcelona inner shelf (NW Mediterranean): A small Mediterranean river- and wave-dominated system

The seasonal pattern of sediment dynamics on an inner shelf characterized by the presence of sediment delivered by a small, mountainous river (with a “flash-flood” regime) was investigated. Near-bottom suspended sediment fluxes across the shelf (i.e. 20, 30 and 40m water depth) were estimated using observations from three benthic tripods deployed from September 2007 to June 2008. Near-bottom sediment resuspension was controlled by wave-induced currents and river-born sediment availability, whereas the shelf currents played a secondary role. Fourteen sediment transport events were identified (eight in autumn, two in winter and four in spring), with transport rates according to storm intensity and sediment availability. These few energetic events induced a large percentage of the cumulative sediment transport near the bottom. However, the lack of proportionality between suspended sediment transport rates and the combined wave-current bottom shear stress in some events highlights the importance of the sequence of events in sediment dynamics. Since wave activity, hydrography and river discharges display a strong seasonal pattern in the NW Mediterranean, the resulting sediment dynamics across the shelf also correspond to a seasonal cycle. This seasonal variability leads to a temporal evolution of the bottom grain size (coarser in winter) and the near-bottom sediment transport rates (higher in spring and autumn) which is consistent with the seasonal pattern of the hydrodynamic events and the river discharge load.

Sediment transport partitioning in the swash zone of a large-scale laboratory beach

Swash zone sheet flow and suspended sediment transport rates are estimated on a coarse sand beach constructed in a large-scale laboratory wave flume. Three test cases under monochromatic waves with wave heights of 0.74m and wave periods of 8 and 12.2s were analyzed. Sediment flux in the sheet flow layer exceeds several hundred kgm−2s−1 during both uprush and backwash. Suspended sediment flux is large during uprush and can exceed 200kgm−2s−1. Instantaneous sediment flux magnitudes in the sheet layer are nearly always larger than those for suspended sediment flux. However, sediment transport rates, those integrated over depth, indicate that suspended load transport is dominant during uprush for all cases and during the early stages of backwash except in the case for the 12.2s wave case when the foreshore was steeper. Results could not be obtained for an entire swash event and were particularly truncated during backwash when water depths fell below the elevation of the lowest current meter.

Determining Spurious Correlation between Two Variables with Common Elements: Event Area-Weighted Suspended Sediment Yield and Event Mean Runoff Depth

Spurious correlation is a classic statistical pitfall pervasive to many disciplines including geography. Although methods of calculating the spurious correlation between two variables possessing a common element in the form of sum, ratio, or product have been developed for a long time, controversial assertions on whether the spurious correlation should be treated or ignored are still prevalent. In this study, we examined this well-known but intriguing issue using the data representing two nonindependent variables, event area-weighted suspended sediment yield (SSYe) and event mean runoff depth (h). By transferring the correlation between SSYe and h to that between suspended sediment transport rate (Qs) and water discharge (Q), we developed a new method of determining whether Qs is truly correlated to Q. The method involves calculating coefficients of spurious correlation () and the associated “pure” spurious correlation (), a hypothesis test, and regression between and . Our analysis showed that (1) there exists a true correlation between SSYe and h and (2) the spurious correlation is strongly related to the variability of the variables. We then proposed a general rule stating that the apparent spurious correlation between two variables could be ignored if the two have a true causal relation. At last, we distinguished the difference between spurious correlation and spurious reference.

Suspended sediment transport in the Magdalena River (Colombia, South America): Hydrologic regime, rating parameters and effective discharge variability

The Magdalena River has the greatest length (1612km) and drainage area (257400km2) of any river system in Colombia, and its watershed occupies 24% of the Colombian territory. The river originates in the Andean Cordillera at an elevation of 3685m and flows to its mouth in the Caribbean Sea (Bocas de Cenizas). For this study, information on daily flow discharge (Q), suspended sediment transport (Qs) and mean suspended sediment concentration (Cs) from 1990–2010 for the Magdalena River, based on measurements at the Calamar gauging station (the closest station to the mouth), was provided by the Institute of Hydrology, Meteorology and Environmental Studies of Colombia (IDEAM in Spanish). The mean annual suspended sediment load was 169±73×106tyr−1 for the period from 1990–1999 and 145±47×106tyr−1 for the period from 2000–2010, amounting to a 14% reduction in the suspended sediment transport rate between the two periods. The sediment rating curve (Qs=aQb) was also evaluated for these two periods (1990–1999 and 2000–2010). An analysis of the regression coefficients (a, b) for the two periods showed a decrease in b and an increase in a after 1999, which coincides with a decrease in suspended sediment transport. This change might be attributed to natural factors, including the accumulation of sediment in the Depresion Momposina and variation in hydro-climatological patterns in the Caribbean region. Decreases in effective transport were confirmed using three methods (Log-Normal and Normal distribution, and magnitude-frequency histogram) for the study period.

Bedform contributions to cross-shore sediment transport on a dissipative beach

Field measurements of hydrodynamics, suspended sediment transport rates and bedform sediment transport rates were made in the intertidal section of a dissipative sandy beach (D50=0.26mm, slope=1/80) at Perranporth (UK). Pressure transducers, acoustic Doppler velocimeters, optical backscatter sensors and an acoustic sand ripple profiler were deployed for 12 tides, measuring in a range of wave heights from 0.5 to 2.2m, water depths from 1 to 6m, and in current strengths up to 0.4m/s. Data were analysed in terms of the distance to shore (x) normalised by the surf zone width (xs), and spanned the region 0.4<x/xs<3. Bedform heights up to 30cm and wavelengths 0.5 to 2.7m were recorded. Maximum wavelengths were observed just shoreward of the breakpoint. Bedforms were classified as sub-orbital, vortex ripples. Bedform migration was mostly onshore directed, and correlated with positive (onshore) wave skewness. Migration rates increased through the shoaling zone to a maximum of 1.5cm/min just shoreward of the breakpoint (x/xs=0.8). The bedform component of sediment transport was generally onshore directed, and maximum just shoreward of the breakpoint (0.021kg/m/s). Point measurements showed that the cross-shore suspended sediment transport 25cm above the bed was dominated by the mean component, with an offshore directed maximum at x/xs=0.5. Contributions to onshore transport were only made by the incident wave (gravity band) component. The total depth integrated suspended sediment transport was offshore directed and maximum in the mid surf zone (−0.16kg/m/s). The depth integrated suspended sediment transport dominated over the bedform sediment transport in the inner to mid surf zone (x/xs<0.5) and in the outer shoaling zone (x/xs>1.5). The fractional contribution of the shoreward directed bedform transport to the total absolute transport was up to 100%, and occurred broadly in the region of the breakpoint (0.5<x/xs<1.5). However, spatial averaging in the cross-shore indicated that a more realistic bedform contribution was up to 15% of the transport, with a maximum at x/xs=0.9. Results from this dissipative beach experiment generally agree with previous findings on intermediate beaches, steep beaches, and offshore sandbars.

Soft shore protection methods: The use of advanced numerical models in the evaluation of beach nourishment

Beach nourishment is one of the worldwide most common soft shore protection methods. However, the design of these projects is usually based on empirical equations and rules, leaving large margins of error regarding their expected efficiency. In the present work, an advanced wave and sediment transport numerical model is developed and tested in the evaluation of beach nourishment. Non-linear wave transformation in the surf and swash zone is computed by a non-linear breaking wave model based on the higher order Boussinesq equations, for breaking and non-breaking waves. The new Camenen and Larson (2007), transport rate formula for non-cohesive sediments (involving unsteady aspects of the sand transport phenomenon) is adopted for estimating the sheet flow sediment transport rates, as well as the bed load and suspended load over ripples. Suspended sediment transport rate is incorporated by solving the 2DH depth-integrated transport equation. Model results are compared with experimental data of both profile (cross-shore) and planform morphology evolution; the agreement between the two is considered to be quite satisfactory.