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Numerical models can be powerful tools for evaluating the best scenarios for the construction of artificial nourishments to mitigate coastal erosion. Until recent decades, when looking at medium- to long-term simulations, cross-shore and alongshore processes have been studied separately. Accounting for both processes in a shoreline evolution numerical model would improve the understanding and predictive capacity of future changes in coastline evolution. The AX-COAST project aims to develop new capacities in modeling cross-shore sediment transport processes by adding the CS-Model, a cross-shore numerical model, into the existing LTC (Long-Term Configuration) model. The LTC model is a shoreline evolution numerical model which is a module of the cost–benefit assessment tool COAST. This work presents the first steps of the CS-Model implementation, which involve evaluating its performance by calibrating the model with extensive measured datasets of wave climate, beach profiles, tide levels, etc., from coastal areas in IJmuiden and Sand Motor in the Netherlands. The results show good agreement between modeled and observed values. Additionally, wave climate datasets derived from global and regional wave models were considered to evaluate modeling performance at IJmuiden. Using derived timeseries from the wave models did not significantly lead to different results compared to using measured data. The obtained mean absolute and relative errors for each profile were low for both types of datasets. Calibration processes with consistent data are important in modeling simulations to accurately represent the study area and ensure the credibility of future simulations. [ABSTRACT FROM AUTHOR]

Abstract: The processes responsible for sediment transport and morphological change in the intertidal zone of natural beaches are not well known. Consequently, factors determining whether the intertidal beach erodes/accretes or remains stable in the face of significant wave impact, and the mechanisms behind the elusive concept of ‘equilibrium beach slope’ are poorly understood. A field experiment was designed to measure suspended sediment transport in the swash and inner surf zone through successive tidal cycles in the intertidal zone at Egmond Beach, The Netherlands, using a stack of fiberoptic backscatter sensors (UFOBS-7). The experimental period comprised three large storm events, including an extreme storm with offshore significant wave heights in excess of 7 m. Surveys spanning a >1 km long section of the beach as well as observations from an ARGUS video camera system showed that gently sloping shoreline salients (megacusps) were highly stable in position and displayed only minor slope adjustments through the storm period, whereas steeply sloping embayments were eroded significantly. The sediment transport measurements at a shoreline salient indicated that the subdued net beach response was because offshore sediment transport occurring under surf zone conditions at high tide was compensated by onshore sediment transport at low tide when swash zone processes dominated. Such temporally varying, tidally modulated sediment transport rates and directions are suggested to be able to maintain a quasi-equilibrium intertidal beach slope and the results indicate that a negative feedback existed between initial beach slope and net sediment transport patterns. [Copyright &y& Elsevier]

A man-made dune-beach-spit system at the south-east side of the island of Texel (Prins Hendrik site) has been built in 2018–2019 to strengthen the traditional dike. The core of the dune-beach-spit system consists of medium fine sand with a d 50 of 0.25–0.3 mm. The beach is covered with an armour (protection) layer of coarse materials with relatively large gravel and shell fractions to reduce wind erosion and thus maintenance costs. In the design phase of the project the aeolian sand transport model of Bagnold was used to estimate the long-term erosion losses of sand at the new dune-beach system. This transport model was validated in the design phase by using detailed sand transport and bed roughness measurements at a nearby site called The Hors. This site is a wide natural beach plain of sand (d 50 = 0.23 mm), where 147 high-quality datasets have been collected using a wind mast equipped with 5 cup anemometers and various sand traps. It is shown that the measured sand transport rates at the Hors can be reasonably well represented by the modified Bagnold-equation for dry sand. After completion of the new dune-beach system, a field experiment was performed at the Prins Hendrik site to verify the sediment transport predictions and erosion loss of sand. Data from two permanent wind masts and one short, mobile wind mast were used to derive the effective roughness of (stationary) bed forms. Sand transport rates were measured at various locations using a new trap sampler. The measured sediment transport in the armoured beach zone can be reasonably well represented by the Bagnold-equation using a multi-fraction approach with hiding-exposure coefficient. The predicted transport rates have been used to estimate the annual loss of sand from the Prins-Hendrik site. • Aeolian transport in conditions with sand, gravel, shells and bed forms is studied on Texel, the Netherlands. • Using the measured overall shear velocity leads to overprediction of transport rates. • Using a multi-fraction approach, transport rates in armoured conditions can be reasonably well predicted. • Transport rates on a sandy beach can be significantly reduced (factor 3 to 4) by the placement of an armour layer. [ABSTRACT FROM AUTHOR]