Morphological effects of buildings in a sandy beach environment

Worldwide, many houses, restaurants and other buildings are present at the beach. These buildings alter the airflow and windblown sediment transport in their surroundings. This causes patterns of deposition and erosion around buildings, which can block e.g. roads or beach entrances. Possible repercussions for the larger beach environment arise because deposition around buildings imply that windblown sediment transport is intercepted. This reduces sand influx into the dunes, thereby affecting coastal safety.
Coastal managers are responsible for regulation on beach buildings, and decide where, when and if buildings can be placed. This requires a proper understanding of how beach buildings shape their environment, and especially how this depends on building properties that can be addressed by regulation. Therefore, this thesis aims to determine and understand quantitatively how buildings at a sandy beach affect the wind-driven morphological development of the beach environment.
Using field experiments, the initial deposition and erosion patterns around buildings were examined. By placing cuboid scale models of buildings at the beach, the shape and size of these patterns were linked to building geometry. Next, the field experiments were extended to determine the effect of wind orientation and the bed pattern around building groups at various building spacings. Finally, interactions of building-induced bed patterns with natural bedform dynamics were studied. Hereto building effects were added to an existing cellular automaton computer model for sandy aeolian landscapes. Next, model results were compared to our field experiments, followed by longer-term simulations to explore building-bedform interaction for periods of up to 15 years.
Overall, this study has revealed that systematic relations exist between the geometric characteristics of buildings – individual buildings and building groups – and the induced aeolian deposition and erosion patterns. Quantitative relations were derived for the horizontal extent of the initial deposition patterns and for the asymmetry of the deposition tail lengths. For building groups, three building spacing regimes were identified, each with different morphological patterns around buildings. The long-term simulations illustrate how interactions of building-induced effects with aeolian bedform dynamics can alter dune development. These findings contribute to the much-needed scientific support for regulations for permitting buildings on the beach.