A detrital sediment budget of a Maldivian reef platform

- Provides measurements of platform surface and fore-reef slope sediment transport.
- Sediment fluxes were high in the absence of large-scale storm activity.
- Regional climatic oscillations drive reversals in net sediment transport.
- Total off-reef export (sand and gravel) estimated at 127,120 kg y-1.
- Detrital sediment deposits act as temporary stores of carbonate material.

Sediment dynamics are an important control on the morphology and development of reef systems by actively removing and redistributing excess detrital sediment. This study presents quantitative data from direct point measurements of sediment transport on the platform surface and fore-reef slope of Vabbinfaru reef, North Malé Atoll, Maldives. A suite of sediment traps were used to construct actual rates of platform sediment fluxes and off-reef export over different spatial and temporal (seasonal) scales to establish key sediment transport pathways. Findings showed that high sediment fluxes occur on Vabbinfaru platform in the absence of major storm activity (up to 1905 g m− 1 d− 1), with 95% of annual transport occurring during the southwest monsoon as a result of increased wave energy. Climate-driven changes in the platform process regime caused a reversal of net sediment transport pathways between each monsoon season. Off-reef export rates were high, reaching a maximum of 12.58 kg m− 1 y− 1 for gravel and 407 g m− 1 d− 1 for sand-sized sediment. An estimated 127,120 kg is exported from the platform annually equating to a significant loss from the reef sediment budget and contributing to the long-term geomorphic development of the fore-reef slope and atoll basin. Detrital sediment reservoirs on Vabbinfaru are not purely depositional carbonate sinks, but rather temporary stores that are important in the transfer of sediment between reef zones.