Modelling Nature II

The study aims to enhance the understanding of flow structure modulated by a model of a heterogeneous canopy of four different seagrass species under unidirectional currents, and compare these findings with metrics from canopies with a single species to understand the fundamental differences in flow structures.

Large scale (full and half scale) experimental tests were conducted to investigate the performance of four constructed salt marsh edge treatments and their ability to attenuate waves and limit reshaping of a marsh platform. The four tested edge treatments include a natural sand edge, a rounded gravel berm, an oyster-shell filled bag berm and a brushwood dam. A brief summary of the ability to attenuate waves and limit marsh sediment reshaping is provided for each edge treatment.

Nature-based approaches aim to protect coastal ecosystems, but implementing them in urbanized coastal areas is challenging. Biomimetic solutions attempt to imitate natural habitats like kelps, but their use for coastal protection is non-existent due to the complexity of the geometry and hydrodynamic behavior they mimic. This study focuses on   wave dissipation by soft structures, aiming to develop an analytical model for determining new formulations of drag and inertia coefficients, enabling integration into traditional models with less prior parametrisation. The approach relies on the interaction between wave forcing and flexible structure displacement, considering parameters like pulsation, amplitude and phase shift. The new formulation of drag and inertia coefficients will depend on the structure geometry and flexibility, and hydrodynamic forcing. A comparison with existing literature and a dedicated field campaign are used to validate the model.

Coastal dunes, shaped by natural processes, particularly aeolian sediment transport, are dynamic environments where vegetation plays a pivotal role in trapping sediments, enabling dunes to reach substantial heights. However, the biomechanical traits of aboveground dune vegetation have received limited attention, impeding precise modeling in coastal engineering. Understanding dune erosion and accretion is essential for enhancing coastal resilience and the integration as ecosystem-based coastal protection measures. Notably, prior research has primarily focused on salt marshes and seagrass (e.g. Keimer et al. 2023), neglecting more detailed modeling of dune vegetation, often employing simplified methods like live vegetation (e.g. Figlus et al. 2014) or wooden dowels (e.g. Bryant et al. 2019). The hypothesis tested here is that geographic expositions and seasonal growth stages can be quantified for marram grass (Ammophila arenaria), and that in turn, these vegetation characteristics will inform laboratory studies involving the interaction of waves, flexible vegetation and eroding dunes.