Processes that drive of shoreline change in fringing reef systems

Coral and rocky reefs are often considered to be an effective natural barrier that protects coastlines from waves. The three-dimensional structure of a reef dissipates wave energy over relatively short distances, which must ultimately affect the shape of the adjacent coastline. However, precisely how the shoreline profile is affected by the presence of a reef is not well understood and models that are validated to capture this profile do not exist.

A laboratory experiment was conducted in a 55 m wave flume, using a 1:15 scale fringing reef model with both a fixed and movable bed. Four seven-hour irregular wave cases were conducted both with and without bottom roughness elements (schematically representing bottom friction by reef roughness), as well as for both low and high still water levels. The laboratory experiments are compared to results obtained from the numerical model XBeach that was applied in both non-hydrostatic (XB-NH) and surf-beat (XB-SB) modes. Using this combination of laboratory and numerical data, this presentation will discuss how a range of physical processes that are observed in reef environment shape the adjacent coastline as well as how changes to these processes may affect reef fringed coastal areas.