A morphodynamic model of reef-island development on atolls

Reef-islands on the rims of atolls are deposits of unconsolidated reef sediment that have accumulated as a result of sediment transportation processes. Reef-islands appear especially vulnerable to changing environmental conditions particularly regarding the impact of sea-level rise. The morphodynamic processes involved in the development of these landforms, however, are poorly understood and difficult to observe over long time periods. Several conceptual models of reef-island development have been proposed that offer insights into reef-island behaviour, particularly where these models can be implemented in a computational framework. This paper presents an aggregated-scale behaviour-oriented model that simulates sediment accumulation on an atoll rim. A requirement of the behaviour-based modeling approach is that the model parameters need to be determined for each application of the model. An inversion algorithm is used to estimate values for model parameters, including the maximum volume of the island and the sediment production rate. The model provides a framework for experimentation with modes of island development, links sediment production to the observed morphology of the reef-island, and quantifies the limits to reef-island development.