Search

This study presents 62 years of hindcast wave climate data for the south coast of Sweden from 1959–2021. The 100-km-long coast consists mainly of sandy beaches and eroding bluffs interrupted by headlands and harbours alongshore, making it sensitive to variations in incoming wave direction. A SWAN wave model of the Baltic Sea, extending from the North Sea to the Åland Sea, was calibrated and validated against wave observations from 16 locations distributed within the model domain. Wave data collected from open databases were complemented with new wave buoy observations from two nearshore locations within the study area at 14 and 15 m depth. The simulated significant wave height showed good agreement with the local observations, with an average R2 of 0.83. The multi-decadal hindcast data was used to analyse spatial and temporal wave climate variability. The results show that the directional distribution of incoming waves varies along the coast, with a gradually increasing wave energy exposure from the west towards the east. The wave climate is most energetic from October to March, with the highest wave heights in November, December, and January. In general, waves from westerly directions dominate the annual wave energy, but within the hindcast time series, a few years had larger wave energy from easterly directions. The interannual variability of total wave energy and wave direction is correlated to the North Atlantic Oscillation (NAO) index. In the offshore, the total annual wave energy had a statistically significant positive correlation with the NAO DJFM station-based index, with a Spearman rank correlation coefficient of 0.51. In the nearshore, the correlation was even stronger. Future studies should investigate the possibility of using the NAO index as a proxy for the wave energy direction and its effect on coastal evolution.

Combining hard and soft costal protection solutions can be an appropriate measure to enhance structure lifetime. This study aims to quantify the morphological evolution of the nourished stretch and adjacent coastlines. A small-scale beach nourishment has been performed in front of a rock revetment at site in Faxe Ladeplads in Zealand, Denmark. The overall objective is to learn more about the dynamics of small-scale nourishments in low energy environments. Monitoring techniques include repeated topographic (Trimble RTK-GPS, drone surveying) and bathymetric (single beam) measurements. To measure the hydrodynamic conditions two surface acceleration buoys deployed at -4 and -7 m water depth were used. Sediment volumes from nourishments of size 70,000 m3 and 20,000 m3 redistributed relatively quickly. The nourished material built up the cross-shore profile and a longshore bar in this area, and distributed sediments in the direction of the dominant littoral drift (SW). Results suggest that the morphological evolution of the nourishment is dependent on local hydrodynamic conditions and local geomorphology. These findings have implications for the main objectives of preventing wave overtopping onto an adjacent coastal road during extreme events and restoring a beach for recreation.

In this study, an efficient numerical model for predicting ship waves was developed using Green’s functions. Avoiding detailed description of the complex boundary conditions around a ship, this mod...

Nearshore complex and energetic hydrodynamic conditions make observing evolving processes during extreme and short-term events difficult. In particular, total sea levels at the coast are hard to measure with current techniques. Sea level is commonly measured with tidal gauges and spaceborne altimetry, which lack essential details of spatial and wave-related sea level variability along the coast. Hence, novel techniques, adapted to nearshore areas, are required. This paper presents the first-time use of video cameras to derive the total sea level at the coast. This novel approach consists of estimating time-varying total water levels by applying a celerity-based depth inversion method, which is conventionally used to estimate bathymetry from video. The video-derived total sea levels are compared to sea levels derived from an in situ acoustic Doppler current profiler (ADCP), the nearest tide gauge, and altimetry. A tidal harmonic analysis is performed on the video-derived water levels, yielding an accurate determination of the dominant tidal harmonics. However, it remains difficult to separate bathymetric changes due to the waves on beaches when rapid morphological changes occur under energetic conditions. Nonetheless, video-derived water-level anomalies are in good agreement with state-of-the-art altimetry products. Although there is still work to be done, the results show the potential to measure total sea level at the coast using video camera systems.

This study investigates the impact of beach sediment supply on dune volume evolution through data analysis and model simulations of the Kennemer dunes in the Netherlands. A cross-shore sediment transport model (the CS-model) is applied with local time-averaged longshore sediment transport gradients derived from bathymetric and topographic observations. The model is used to study the relative importance of different transport processes on dune volume evolution, assuming that aeolian transport from the beach to the dune is supply-limited. The wave-driven longshore transport gradients are found to explain a large part of the observed variation in the dune evolution within the study area. In accreting parts of the coast, dunes are growing due to sediment supply from longshore transport, whereas in eroding parts, dune growth depends on supply from artificial nourishments. Seasonal constructions on the beach and vegetation removal from the dunes partly impede dune growth along the considered stretch of coast. The model performance is satisfactory, being able to reproduce a considerable part of the large variation in the alongshore dune response observed in the study area. Overall, the results are a promising contribution to the capability of simulating decadal-scale dune evolution, which is important for long-term flood risk assessments and safe designs of nature-based solutions.

The aim of this technical note is to present methods that allow for direct computation of the bed roughness due to sediment transport based on a formula developed in the literature for case...

This paper presents a bottom boundary layer model for the unsteady and non-uniform flow in the swash zone, by extending the momentum integral method so as to include spatial gradients. The developed model is further incorporated into a hydrodynamic model based on the Nonlinear Shallow Water Equations. Two swash zone cases are examined to investigate the effect of the inclusion of spatial gradients. In the first of the two, boundary layer development under non-breaking periodic waves formulated by Carrier and Greenspan (1958) is investigated (wave-driven swash). Results show that the spatial gradients have the most pronounced effect in the lower swash, and in the region just seaward. In both these regions the spatial gradients enhance (diminish) onshore (offshore) bed shear stress, thus potentially contributing to onshore sediment transport under non-breaking waves. The second case investigated is the Kikkert et al. (2012) dam-break swash event (bore-driven swash). The model results are qualitatively and quantitatively accurate when compared against the laboratory measurements, and the velocities in the later backwash agree more closely with the measurements than those of Briganti et al. (2011). Results show that the inclusion of spatial gradients also favours onshore sediment transport in the lower swash. In addition, the bottom boundary layer is more fully developed in the uprush tip, resulting in smaller bed shear stress in the upper swash. The extended momentum integral method thus appears to capture more comprehensively the swash boundary layer, and the approach, therefore, offers a way forward in more accurate reproduction of swash dynamics in computational modelling.

The potential catastrophic event of a landslide bringing contaminants to surface waters has been highlighted in public media, but there are still few scientific studies analyzing the risk of landslides with contaminated soil. The aim of this study is to present a method to estimate the risk of potential long-term ecological effects on water bodies due to contaminated soil released into a river through a landslide. The study constitutes further development of previous work focusing on the instantaneous (short-term) release of contaminants and associated effects. Risk is here defined as the probability of surface water failing to comply with environmental quality standards (EQS). The transport model formulation is kept simple enough to allow for a probabilistic analysis as a first assessment of the impact on the river water quality from a landslide runout deposit containing contaminated soil. The model is applied at a contaminated site located adjacent to the Göta Älv River that discharges into the Gothenburg estuary, in southwest Sweden. The results from the case study show that a contaminated runout deposit will likely cause contamination levels above EQSs in the near area for a long time and that it will take several years for the deposit to erode, with the greatest erosion at the beginning when water velocities are their highest above the deposit. A contaminated landslide runout deposit will thus act as a source of contamination to the downstream water system until all the contaminated deposit has been eroded away and the contaminants have been transported from the deposit to the river, and further to the river mouth - diluted but not necessarily negligible. Therefore, it is important to prevent landslides of contaminated soil or waste, and if such events were to occur, to remove the contaminated runout deposit as soon as possible.

Modelling is an alternative solution to reduce the cost of water quality monitoring. Commonly, concentration of pollutants is estimated based on limited sampling information. Concentration of ions in rivers can be estimated using modelling strategies that involve statistics and artificial intelligence as well as the understanding of physical processes. Therefore, the performance of feedforward neural networks that employs the Levenberg-Marquardt optimization method was compared to the PPBM recently proposed. Both ANN and PPBM were used to estimate the concentration of major ions (Na+, K+, Mg2+, Ca2+, HCO3 −, SO4 2−, Cl−, and NO3 −) in river water based on pH, alkalinity, and temperature. Root-mean-square error and Pearson correlation coefficient (R) together with its p-value were used to evaluate the quality of results of both models. The ANN model provides better estimates compared to the PPBM in most cases. However, the PPBM has the possibility to evaluate its predictions by using the difference between the estimated and measured electrical conductivity. If the predictions are not good the PPBM can be recalibrated, whereas the ANN model is limited in this respect. Another disadvantage of ANN models is that they are developed based on historical data and if limited data are available, such models cannot be used. This latter disadvantage makes the PPBM superior in developing countries, where often little or no consistent historical data exist.

Predicting hydrodynamic forces from ship waves along a waterway is essential for managing a sustainable shoreline in fairways. In this context, a numerical model can be a useful tool for calculating ship waves in fairways with complex geometry. XBeach is a numerical model offering the potential to be a one-tool solution for simulating ship waves from the ship to the shore. However, XBeach has not been evaluated against field measurements of ship waves. Thus, the objective of this paper is (1) to compare XBeach against high-quality field measurements of ship waves and (2) to assess its general applicability to ship wave simulations through an extensive sensitivity analysis with regard to the main input parameters. Water level measurements from 42 passages of the M/S Baltic Princess in the Furusund navigational fairway in the Stockholm Archipelago were chosen to test and evaluate XBeach. The results showed that XBeach was able to generate and propagate the primary and secondary waves. Primary waves were reproduced well with a mean absolute error (MAE) of 3 cm for the drawdown height. The overall secondary wave field pattern was represented by XBeach; however, for the largest, single divergent wave comparison for height, period, and timing showed deviation from the observations. Overall, XBeach was found to be a robust model for ship wave applications, only requiring input data typically available. Sensitivity analysis for a generic hull, derived from the type of vessel studied and with the corresponding dimensions as the real hull, showed similar results enabling robust and reliable simulations without access to detailed technical drawings.

The 2011 Great East Japan Earthquake on March 11, 2011 triggered not only giant tsunami waves, but also caused significant land subsidence followed by land rise in the Sendai Coastal Plain areas. These impacts resulted in severe damages to the coastal infrastructure and induced coastal morphology changes along Japan's northeast coast. It was observed that the maximum downward deformation in the Sendai Coastal Plain was initially about - 0.3 m. Immediately after the earthquake, the land started to rise and it has already recovered back to its original position at some locations after 10 years. Thus, the high-quality measured beach profile data sets after the 2011 Tohoku Earthquake are valuable for exploring the impact of sea level rise (SLR) on shoreline position evolution, since the bed level change is inversely related to the sea level rise process. The data also provide a unique opportunity to evaluate the Equilibrium Beach Profile (EBP) theory and validate the Bruun concept. In the present study, a new simple analytical solution for time-dependent shoreline position response to the tectonic recovery process is developed based on the convolution method. The model results are able to predict the time-dependent shoreline evolution, including the maximum potential response and the characteristic erosion time scale at which the profile evolves towards a new equilibrium state.

A modelling methodology was developed that simulates the resulting pH and alkalinity in the mixing zone when acidic water is discharged into a river. The input to the model are the: pH, alkalinity, flow, and temperature of both the river water and the acidic discharge. Two different scenarios were simulated: (1) a change of pH in the acidic discharge, assuming constant flow; and (2) a change in the flow of the acidic discharge, assuming constant pH. The model incorporates the effect of carbonic acid and the modelled values agree well with the laboratory results. The model setup was subsequently used to predict the anticipated effect of contamination of the Zambezi River in Mozambique. The results indicate that the river will be impacted if the average pH of the water in the tributaries coming from the mining area is below 3. The model could be used by water managers to predict the potential impact of acidic discharges in poorly monitored rivers.

Changes in the inlet morphology of choked coastal lagoons often restrict the water exchange with the sea, making them vulnerable to pollution events and eutrophication processes. In this study, the importance of tides for the water exchange was investigated in Mundau Lagoon, which is a choked lagoon located in northeastern Brazil that has a very dynamic inlet and channel system. The analysis was carried out for critical scenarios during the dry season when the river flow to the lagoon decreases markedly. The concepts of integrated flushing time and spatially distributed residence time scales were applied using a Lagrangian particle tracking approach coupled with a hydrodynamic model. The flushing time of Mundau Lagoon was estimated to be 12.6 days during neap tide and 5.7 days during spring tide, including a return flow factor. Employing an e-folding form, the corresponding value was calculated to be 64 and 54 days for particles allowed and not allowed to return to the lagoon, respectively. The spring tides were responsible for the most pronounced water exchange in the Mundau Lagoon. Different particles release times displayed the effect of the initial tidal conditions on the flushing time; lower exchange times were estimated for releases during ebb tides and spring tides. The integrated estimation of the water exchange when imposing a scenario of most frequent wind conditions indicated a considerable delay caused by this forcing, increasing the flushing time up to 23 days. Another observed effect of the wind was a spatial redistribution of the tidal exchange in the lagoon into different zones with similar residence time.

The 400-km long coast of the Bight of Benin, formed by sand barriers and lagoons, is bordered to the east by the Niger River Delta and to the west by the Volta River Delta and is characterized by several coastal infrastructures, of which the most important are the deep water harbors of Lome, Cotonou, and Lagos. In this study, an enhanced version of the CASCADE coastal evolution model was implemented in order to reproduce the evolution of the coast over the period 2000-2015, considering the presence of coastal infrastructure, inlets, and the reduced sediment influx from rivers. The model results showed simulated coastal response around the main coastal infrastructure in agreement with observed data. In addition, the validated model was used to estimate the amount of sediment needed to control erosion through beach nourishment downstream of the harbors. The impact of reducing sediment input on coastal evolution was investigated through model parameterization of the influx at the boundary. Overall, the model may be a useful tool for improving regional coastal policies in the Bight of Benin.

Thirty-nine years of high-resolution data from 1981 to 2019 surveyed by the Field Research Facility (FRF) of the US Army Corps of Engineers at Duck, North Carolina, in the United States, were analyzed for temporal and spatial characteristics of beach morphology evolution employing a range of statistical methods. In the study, emphasis was put on the response of the subaerial part of the beach profile to waves and water levels at several different spatial and temporal scales, ranging from weekly to decadal response. The profile data set was analyzed to determine the subaerial beach evolution, including both the influence of cross-shore sediment transport related to storms and the longshore transport affected by the FRF research pier. The analysis showed that adjacent profile lines exhibit similar beach morphology and evolution with high correlation regarding spatial and temporal patterns. The pier has a noticeable influence on the longshore sediment transport leading to erosion downdrift and accretion updrift of the pier; the dune in the FRF region is rather stable and resistant towards storm erosion, requiring combinations of runup height and water level (i.e., runup level) that reaches the dune face; and erosion high up on the subaerial part of the beach, including the dune, occurs on average due to storms with a return period of 5 years.

Dredged material resulting from deepening and maintenance activities of the Aveiro Harbor inlet channel, northwestern coast of Portugal, has been used to mitigate the erosion trend recorded on nearby beaches (from Barra to Costa Nova Beach) through direct placement of sand by using standard dredge equipment. The disposal activities of dredged material have been undertaken at two main sites: between the south breakwater and the 1st groin of Costa Nova (dumping area 1, DA1) and between the 3rd and the 5th groin of Costa Nova (dumping area 2, DA2).The sand was placed in the nearshore, between the −2 and −7 m Chart Datum, CD, contours. In this study, short- and long-term coastal morphologic changes in the sea bottom, in response to several nourishment operations and to the incoming waves, within the dumping area boundaries are investigated based on a data set of hydrographic surveys collected annually, just before and after the nourishments, between 2009 and 2015. Preliminary results describing the main morphologic changes, evolution trends, sediment budget variations, and nourishments performance are discussed using mainly Geographic Information System techniques. Overall, the analysis demonstrates that the short-term losses in the dumping areas (one month of interval) can reach 50% of the nourished volume, revealing a significant movement of the fill material towards offshore. Seasonal variations promoting cross-shore material exchange can also prevail and misrepresent the sediment balances, if the monitoring area is not comprehensive. Furthermore, some bathymetric analysis suggested that longshore transport gradients have moved the fill material from Barra beach to downdrift areas. All the obtained results contribute to the ongoing discussion about the effectiveness of nearshore sand placements especially in context of an energetic environment.

This paper presents a two-dimensional numerical model of nearshore random wave transformation with a focus on model calibration and verification with both laboratory and field data. The model is based on the energy balance equation including diffraction and dissipation terms (Mase, 2001). The energy dissipation is determined based on the formulation by Dally et al. (1985), with new expressions for the stable wave height and decay coefficients. These coefficients are estimated based on the local beach slope and offshore wave conditions. The model is calibrated with several data sets from the Large-scale Sediment Transport Facility (LSTF) at the Coastal and Hydraulics Laboratory in USA. Then, the model is verified against a large number of data sets, including LSTF data for cases with structures, laboratory data from the Great Wave Flume in Hanover, the field data from Egmond in the Netherlands, Duck in USA, and Cancun in Mexico. The validation showed that the model could reproduce the observations well. The relative root-mean-square error varies from 5% to 7.6% for laboratory data, and from 10.3% to 18.6% for field data. The coefficient of determination varies from 0.81 to 0.97, demonstrating good agreement between the model and the measurements.

Coastal areas such as beaches with steep upper slope and flat low-tide terrace, are expected to be increasingly affected by sea level changes. Related impacts due to the paramount rise in sea level have been intensively investigated, but there is still little evidence of the impact of shorter timescales variations on the coast, particularly those induced by trapped coastal waves. Using the latest advances in video bathymetric estimation, daily observations over 3.5 years (February 2013 to June 2016) on Grand Popo Beach (West Africa) reveal that intraseasonal sea level variations impact the beach profile. The intraseasonal sea level variations are dominated by the propagation of wind forced coastal trapped waves with periods ranging 15–95 days. It is shown that the beach goes through a transient state with a deformation of the profile: an intraseasonal sea level rise leads to a 2 m erosion of the upper beach and a widening of the flat terrace at the lower beach. Although the underlying mechanism must be tested through beach profile modelling, this study highlights the active adaptation of the beach profile to variations in sea level.

A new parameterization for calculating the nonlinear near-bed wave orbital velocity in the shallow water was presented. The equations proposed by Isobe and Horikawa [1] were modified in order to achieve more accurate predictions of the peak orbital velocities. Based on field data from Egmond Beach in the Netherlands, the correction coefficient and maximum skewness were determined as functions of the Ursell number. The obtained equations were validated against measurements from Egmond Beach, and with laboratory data from small-scale wave flume experiments at Delft University of Technology and from large-scale wave flume experiments at Delft Hydraulics. Inter-comparisons with other previously developed parameterizations were also carried out. The model simulations by the present study were in good agreement with the measurements and have been improved compared to the previous ones. For Egmond Beach, the root-mean-square errors for the peak onshore (uc) and offshore (ut) orbital velocities were approximately 21%. The relative biases were small, approximately 0.013 for uc and &minus, 0.068 for ut. The coefficient of determination was in the range between 0.64 and 0.68. For laboratory experiments, the root-mean-square errors in a range of 7.2%&ndash, 24% for uc, and 7.9%&ndash, 15% for ut.

International audience; The Bight of Benin coast is marked by the presence of three deepwater harbours which have affected the stability of the shoreline. In addition, several studies pointed out the overall diminution of sand supply due to the dams on Volta river channel and climate change effects. The combination of all these factors leads to a mixture of natural and artificial components affecting the coastline evolution in regional and long term scales. Here, we modeled the shoreline in the Bight of Benin, using the CASCADE model. The results show that the overall shape is well maintained and shoreline changes pretty well reconstructed. But, unresolved detailed information did not allowed to consider cross-shore sediment exchange and local deviations can be observed. However, the CASCADE model can be used to investigate regional and long term solutions for decisions-makers in the concerned countries.

The aim of this study was to develop a morphological model for long-term inlet evolution to be applied using a minimum amount of input data and requiring low computational costs. The model was implemented numerically and then validated for a real inlet application: Mundau inlet (northeastern Brazil), a dynamic inlet with a marked freshwater seasonality and alongshore sand transport, reduced by reef sheltering. The model performance was verified, over a total period of 11 years, comparing the simulated inlet width with Landsat and Google Earth images. The simulated inlet channel morphology presented a satisfactory agreement with observations. With the low computational costs, the developed model represented a reliable approach with demonstrated potential to be applied in the quantitative assessment of inlet evolution over long time periods. (Less)

Analysis of a 13-year long, high-resolution data series on beach profiles, surveyed from 1981 to 1993 by the Army Field Research Facility (FRF) at Duck, North Carolina, in the United States, was analyzed in order to understand the temporal and spatial characteristics of the dune response. Various statistical methods were employed in this analysis. The profile survey data set was analyzed with regard to sand volume change and its relationship to seasonal storms and aeolian sand transport. The results showed how the sediment transport and morphological change of the dune were driven through the combined action by waves, water levels, and wind.

This study investigates the relationship between grain-size distributions and sediment transport processes at Angelholm Beach in southwest Sweden. In total, 308 longshore and cross-shore distributed sediment samples are analysed with respect to median grain size and sorting. The longshore sediment transport is almost unidirectional from north to south. Its gradients cause erosion in the north and accretion in the south. The longshore transport sorts the sediment, leading to coarsening in eroding areas and deposition of finer sediment in accreting areas. In the eroding part of the beach, the aeolian transport is limited, and the median grain sizes on the beach are coarser than in the dunes. In the accreting part of the beach, where the dunes are prograding, sediment within the range of dune-building grain-sizes is mostly available at the beach. The results support that sediment supply of appropriate grain sizes is an important factor controlling the long-term dune evolution. (Less)

The salinity in a coastal lagoon is a crucial abiotic factor to the species adapted to the brackish water; for example, this is the case for bivalve mussels that have growth and survival rates critically dependent on the salinity. Lagoons with marked river flow seasonality can be periodically flushed to very low salinity levels during the rainy season. In addition, their water exchange with the sea can be very limited, especially for choked lagoons, making the recovery of the salinity levels slow. In this study, models of the salinity dynamics in a choked lagoon for both monthly and intertidal scales were developed. The intertidal model was used to simulate the salinity drop and recovery processes due to runoff events, while the monthly model was coupled with a newly developed heuristic population model for the bivalve mussel Sururu (Mytella falcata ). Thus, the impact of the salinity interannual seasonality on the mussel population was qualitatively investigated. The intertidal model estimated the expected time to be 19 days for the salinity to recover to levels prior to a runoff event with peak flow higher than 500 m3/s. The monthly salinity model satisfactorily represented the interannual seasonality when applied to a historical record including periods of critical salinity levels. The use of the mussel population model indicated that the Sururu stocks during this period were considerably reduced; however, the model results do not indicate the disappearance of this mussel for more than one rainy season. The models developed showed the potential to be used for the management of coastal lagoons and to investigate future scenarios of changes in the lagoon water balance and forecasted sea-level rise. The analytical models presented also showed potential to be used in guidelines for developing and verifying numerical models capable to represent the salinity effects on mussel populations.

A model developed to describe long-term cross-shore (CS) exchange of sand and resulting profile evolution at regional scale was employed to simulate the evolution at three different sites. The model consists of modules for calculating dune erosion and overwash, bar-berm material exchange, and dune build-up by wind-blown sand transport, as described in detail in a companion paper (Larson et al., 2016). Selected study sites represent coastal stretches influenced by beach nourishment (Barra in Portugal), overwash and breaching (Macaneta spit in Mozambique), and dune development (Angelholm in Sweden). The model applications showed overall good performance and the results of the simulations are promising. Due to limitations in data availability in Angelholm and Macaneta, values on calibration parameters were mainly determined based on previous studies. For Barra, where more field measurements were available, the application showed good agreement between the simulated results and observations. The CS-model proved to be a useful tool to predict long-term evolution of beach-dune systems in a time perspective from years to decades. However, additional efforts should be directed towards improving the schematized model profile so that it can better represent other beach shapes such as a sloping berm or a barrier shape.

A model is developed to simulate the cross-shore (CS) exchange of sand and the resulting profile response at decadal scale to be used in regional coastal evolution models. The CS model consists of modules for calculating dune erosion and overwash, wind-blown sand transport, and bar-berm material exchange. The sand transport equations included in these modules are formulated based on relevant physics in combination with empirical observations and then validated towards laboratory and field data. In order to couple the transport equations to the evolution of key morphological features describing the profile a set of sand volume conservation equations are employed and solved together with the transport equations. The features that are modeled include dune height (from dune foot to crest), the locations of the landward dune foot, seaward dune foot, berm crest, and shoreline as well as the longshore bar volume. The CS model is employed and tested at three different field sites in a companion paper (Palalane et al., 2016), whereas in the present paper the properties of the model are demonstrated by simulating the evolution of the dune, berm, and shoreline in connection with accretion and erosion of sand in a groin compartment. This case derives from a study at Westhampton Beach that focused on shortening the length of a number of groins in order to release accumulated sand in the groin field to eroding downdrift beaches.

This paper presents a numerical model designed to simulate subaqueous cross-shore profile behavior, including response of feeder mounds and barred systems. The present model development builds on the semi-empirical model proposed by Larson et al. (2013), designed to simulate the evolution of longshore bars exposed to incident waves, as well as the exchange of material between the bar and the berm region. Here, efforts are made to expand the theory for the evolution of a single-bar to a 2-bar system, where the volumes of the individual bars (inner and outer) and their responses are modeled. In order to investigate the predictive capacity of the model, this exploratory numerical tool is first calibrated and validated against data from Duck, North Carolina, USA, where 2 bars typically appear (inner and outer). Field data derived from nearshore sand placement projects (Silver Strand State Park, California, and Cocoa Beach, Florida, USA), involving the construction of artificial longshore bars, are also employed to test the model in complex situations with diverse wave climates and typical beach profile shapes. The study presented in this paper shows that the equilibrium-based model is skilled at predicting the time-varying volume of the outer bar (e = 0.39; NMSE = 0.24), suggesting that this morphological feature is strongly influenced by offshore wave forcing in a predictable, equilibrium-forced manner. Model skill was lower (e = 0.51; NMSE = 0.29) when predicting the inner bar evolution at Duck, remaining questions about the predictability and the equilibrium-driven cross-shore behavior of more transient features. Model prediction of the evolution of feeder mounds (artificial bars) proved to be also successful through description of hypothetical bars characterized by zero equilibrium bar volume, leading to a good agreement with the field observations. Overall, the potential for using rather simple models to quantitatively reproduce the main trends of cross-shore volume changes in bars in a time perspective from years to decades has been demonstrated.

In the present study, a morphological model based on the main governing processes of inlet channels was developed for application in long-term simulations, requiring minimum data on forcing and only key information on the inlet geometry. The model considers the balance between the inlet sand transport due to tides and river flows and the longshore transport due to breaking waves. The resulting equations were numerically implemented and validated first through schematic simulations and then through an application to a real inlet. For the schematic simulations, the sediment transport rates in the inlet and alongshore were maintained constant and the behavior during evolution towards equilibrium was investigated and qualitatively assessed. Then, the model was applied to Mundau Lagoon inlet (Brazil), a natural inlet sheltered by reefs and with a marked seasonality in river runoff. Thus, the model performance was validated for a complex setting over time scales of decades through comparisons with the observed inlet evolution determined from satellite images. The calculated results of inlet channel morphological evolution exhibited satisfactory agreement with observations. The computational efforts were low making the model suitable for long-term simulations where many alternative scenarios may be explored in a probabilistic manner. In conclusion, the developed model yielded robust and reliable simulation results having the potential for use in the assessment of long-term inlet channel evolution.

This study presents a deterministic, lumped model to simulate mesoscale sustainable drainage systems (SuDS) based on a conceptualization of the stormwater control measures (SCMs) making up the system and their influence on the runoff process. The conceptualization mainly relies on parameters that are easily quantifiable based on the physical characteristics of the SCMs. Introducing a nonlinear reservoir model at the downstream end of the SuDS results in a fast model that can realistically describe the runoff process at low computational cost. Modelled hydrographs for the study area in Malmo, Sweden, matched data with regard to the overall shape of the hydrograph as well as the peak discharge and lag time. These output parameters are critical factors to be considered in the design of large systems consisting of mesoscale SuDS. The algebraic foundation of the developed model makes it suitable for large-scale applications (e.g., macroscale), where the simulation time is a decisive factor. In this respect, city-wide optimization studies for the most efficient location and implementation of SuDS are substantially accelerated due to fast and easy model setup. Moreover, the simplicity of the model facilitates more effective communication between all the actors engaged in the urban planning process, including political decision makers, urban planners, and urban water engineers.

A numerical model for simulating beach-dune evolution at decadal to centennial time scales is developed. The work builds on an existing semi-empirical cross-shore model, the CS-model, to which the effect of sea level rise is added and the routines for aeolian transport and morphological dune evolution are improved. The model development is based on established conceptual models from the literature, which are translated into mathematical formulations and solved numerically. The capability of the proposed model is demonstrated through a case study at Ängelholm Beach, Sweden. The model is calibrated and validated against a seven-year long data set on morphological evolution and sediment grain-size samples. Beach and dune evolution is then simulated from 2018 to 2100 for a range of sea level rise scenarios. The model results are promising, and suggest that the model has potential to be used for long-term assessment of climate change impact on beaches and dunes.

A one-dimensional mathematical model is presented that describes the cross-shore evolution of a long linear mound of noncohesive sediment placed in the nearshore and exposed to non-breaking waves. The equation for the transport rate accounts for wave asymmetry and gravity, and the net rate is expressed by reference to an equilibrium profile shape. Simplifications reduce the governing equation for mound evolution to the diffusion equation, for which analytical solutions are available for various initial shapes of the mound. Temporal and spatial dependencies governing mound evolution are obtained from the analytic solutions; for example, a doubling of the wave height implies a certain mound response in 1/8 of the time compared to the original conditions. The governing equation is also solved numerically in order to avoid schematization of the forcing, initial, and boundary conditions. Both the analytical and numerical models are compared with data on mound evolution from several sites around the world. Model predictions agree with trends in measurements of four mounds at widely different sites. An example is given concerning the application of the analytical model for preliminary mound design. The formulation presented also applies to infilling of dredged trenches with lengths much greater than their widths. (Less)

Zambezi River Basin is located in Southern Africa. It is essential for the economy of its eight riparian countries. The delta and almost 11% of its total catchment area are located in Mozambique. The main stream of the river receives a run-off contribution of 1800 m3/s in Mozambique and reaches the ocean with a flow of about 4100 m3/s. Coal mining is developing fast in the Zambezi River Basin in Mozambique due to favourable geological conditions. The coal mining and other activities have an impact on the surface and groundwater quality of the river basin. ARA-Zambeze is the river basin organization responsible for the water quality monitoring in Zambezi River Basin in Mozambique. In spite of limited resources ARA-Zambeze performs surveillance monitoring, while the institutions influencing the water quality of the river are doing operational monitoring. In this paper a monitoring system for the Zambezi River Basin in Mozambique is proposed. The system includes two alternative monitoring procedures. One procedure considers improvement of the current situation, which is characterized by multiple actors doing monitoring in isolation, by standardizing the analytical methods and improving data sharing through a web-based reporting system. The other proposed monitoring procedure considers a centralized approach, by having a consulting company doing the monitoring for the whole river basin in Mozambique. The second option has the advantages of improving consistency and comparability of the data, thereby allowing for more accurate trend analyses. It is concluded that the best way forward is to implement the first procedure and slowly move to the second.

Zhang, J.; Larson, M., and Ge, Z.P., 2020. Numerical model of beach profile evolution in the nearshore. Journal of Coastal Research, 36(3), 506–520. Coconut Creek (Florida), ISSN 0749-0208.A numerical model was developed to simulate hydrodynamics (waves, currents, and mean water level), cross-shore sediment transport, and beach profile evolution in the nearshore assuming negligible longshore transport gradients. Particular focus was put on describing the response of the subaerial region of the profile, including the foreshore and the berm, as well as the exchange of material between the swash and the surf zone. The model consists of different modules describing wave transformation, cross-shore currents, mean water elevation, and cross-shore sediment transport. For the purpose of model calibration and validation, detailed, high-quality data on hydrodynamics and beach profile response from the SUPERTANK data collection project were employed. The experimental cases studied encompassed several types of profile evolution, including berm erosion and bar formation, berm flooding and erosion, and offshore mound evolution for a narrow- and broad-crested mound. Overall, good agreement was obtained between calculations and measurements, especially for the foreshore and the berm, whereas the calculated bar shape was smoother than the measured shape. The model produced robust and reliable predictions of cross-shore transport and profile evolution for the cases investigated. Subsequent work in model development will involve dune erosion and overwash as well as validation toward field data.

A semi-analytic model is developed to describe the flow through an inlet between a lagoon and the sea due to a simple tide and the related morphological response of the inlet. The governing equation for the water level variation in the lagoon is derived from the continuity and momentum equations and then solved for quasi-steady conditions yielding analytic expression for the main flow-related properties such as lagoon amplitude, maximum and mean inlet velocity, tidal prism, and retention time. These quantities are expressed in non-dimensional form, where the repletion coefficient is the main independent variable. A sediment balance model is formulated for the inlet that relates changes in the inlet cross-sectional area to the difference between the longshore sediment transport and the transport through the inlet because of the tidal motion. This balance equation can be solved to yield the conditions at equilibrium as well as the evolution towards equilibrium or closure. The semi-analytic model is employed in the balance equation allowing for a close coupling between inlet hydraulics and morphology. Investigation of inlet equilibrium revealed, similarly to the Escoffier curve, two equilibrium situations, one corresponding to stable conditions and one to unstable conditions. The leading parameters in the stability analysis are the repletion coefficient and the longshore transport rate normalized with a fictive inlet transport rate.

A numerical model of undertow due to random waves is developed. The model includes three sub-models: (i) a model for multi-directional and multi-frequency random wave transformation, (ii) a surface roller evolution model, and (iii) a model for calculating the vertical distribution and the mean value of the undertow velocity. The calculation of wave trough level is performed based on a theory for the wave asymmetry. The model was successfully validated against small- and large-scale laboratory experiments. Thus, the model is expected to provide reliable input for the modeling of sediment transport and morphological change due to waves and currents.