The overarching aim of this research is to contribute towards a best practice in modelling meso-scale O(10km), medium-term O(5yrs.) morphological features in Tidal & Estuarine environments. Therefore, various modelling aspects and stages are reviewed. The first pillar argues the need for numerical models in the Geomorphological Engineering discipline on the basis of a brief overview of the historic advances in numerical modelling. Next, the foundation of a numerical model is considered by means of a concise overview of numerical discretisation techniques and their characteristics. We assess the representation of the typical set of physical processes that one may encounter in present-day morphodynamic models and compare their (mathematical) representation following from the underlying choice of discretisation technique. Hereto, we refrain ourselves to the two commonly used methods - finite element and finite difference method. The second pillar gives an overview of the methods that geomorphologists may employ to reduce the model input, and methods to accelerate morphological computations. The last pillar sheds light on different methods that may be applied by geomorphologists to give more insight into the performance of morphodynamic models. These results can, in turn, be of considerable interest in the pursuit to quantitatively validate model predictions. Lastly, this research is concluded with a set of interviews wherein esteemed applied morphodynamic experts were asked about their perception on a possible best practice in modelling skillful meso-scale features in the timeframe of reference. This research hints, therefore, towards an overarching systematic strategy that could be applied by geomorphologists to acquire accurate morphodynamic model predictions on the temporal scale of 5-10 years and for meso-scale features in the order of tens of kilometres.

Ebb-tidal deltas play a key role in the morphology of barrier coastlines and tidal inlet systems as they serve as a natural source of sediment. They are typified by a dynamic morphology that interacts with the adjacent coastlines and sponsors a unique ecological habitat. Under increasing socio-economic, ecological and climate-induced constraints, it becomes imperative to obtain a better understanding of the evolution of ebb-tidal deltas in order to maintain and preserve these morphological features in the near-future time horizon. An increased interest has therefore been raised to understand, quantify and predict the development of ebb-tidal deltas.

In the context of developing a future-proof coastal management and maintenance strategy, the efficiency of ebb-tidal delta nourishments has been further investigated in research programmes such as Coastal Genesis 2.0. For the Ameland inlet, this entailed the construction of a 5 million m3 pilot nourishment over the course of March 2018 to February 2019 and subsequent monitoring in the years following. This research investigates the impact of this pilot nourishment on the natural behaviour of the Ameland ebb-tidal delta. The second goal is to build further knowledge on the modelling capabilities of present state-of-the-art models for the Ameland ebb-tidal delta.

To this end, a process-based Delft3D model is applied to hindcast the morphological development of the ebb-tidal delta with a particular interest in the evolution of ebb-shields and -chutes over the course of 2005 to 2020. It is identified that the representation of the wave-induced processes is key for capturing the development of ebb-shields and -chutes in the model predictions. Therefore, we applied and experimented with an updated nonlinear wave orbital velocity parameterisation and assessed its contribution to the modelling performance.
This thesis demonstrates that the evolution of ebb-shields and chutes on the outer delta is contingent on its initial presence in the initial bathymetry. Hence, the initiation of ebb-shield development is not inherited in the model response. These insights have been integrated and synthesised to assess the application of the present state-of-the-art model as a forecasting tool for the morphological development of ebb-tidal delta nourishments.

Ultimately, it is shown that a model using schematised boundary conditions and an efficient morphological updating scheme is able the predict the yearly-averaged development of the pilot nourishment on the ebb-tidal delta. It is demonstrated that the 2019 pilot nourishment only locally influences the behaviour of the Ameland ebb-tidal delta. Nourished sediment is likely to be redistributed along the ebb-shields, contributing on the long-term to the sediment exchange process with the downdrift coast of Ameland. The location of the ebb-tidal delta nourishment is thereby important for the sediment exchange process and the development of local features. Placing ebb-tidal delta nourishments to the south of the Westgat invokes a primary sediment exchange between the coast of Terschelling and surrounding morphological features. A secondary readjustment of the Westgat thereby influences the development of the ebb-shields and -chutes. Constructing an ebb-tidal delta nourishment north of the Westgat results in a sediment exchange between the local ebb-shields and the downdrift coast of Ameland. Our results also demonstrate that an increase in the pilot nourishment construction height enhances the redistribution of sediment along the ebb-shields.

Lastly, this study identifies further opportunities for improving medium-term morphodynamic models for the Ameland inlet by incorporating time-dependent boundary conditions including new transport formulations such as SANTOSS.