Simulating spatiotemporal aeolian sediment supply at a mega nourishment

Abstract

Mega nourishments are a novel approach to stimulating coastal safety and resilience. Mega nourishments are intended to spread along the coast on a decadal time scale by natural sediment transport processes with a minimum of intrusion into the natural coastal system. The supratidal morphodynamic behaviour of mega nourishments is not well understood due to complexities introduced by limitations in sediment availability to aeolian sediment transport. Consequently, the effectiveness of mega nourishments to stimulate coastal safety and to influence coastal landscape and habitat development remains unknown. In this paper we present a detailed 4-year hindcast of the morphological development of the Sand Motor mega nourishment in The Netherlands. We use the aeolian sediment transport and availability model AEOLIS that focuses specifically on the simulation of spatiotemporal variations in sediment availability. The model includes the recurrence relation between sediment availability and aeolian sediment transport through self-grading and beach armoring. We show that the model is able to reproduce multi-annual aeolian sediment transport rates in the Sand Motor domain in the four years after its construction. The RMSE is 3⋅10⁴m³ (7% of the total sediment accumulation) and R² is 0.93 when comparing timeseries of total sediment accumulation in the dunes, dune lake and lagoon. The combination of spatial and temporal variations in aeolian sediment availability, due to the combined influence of soil moisture, sediment sorting and beach armoring, is essential for an accurate estimate of the total sedimentation volume. The simulated feedback between aeolian sediment availability and transport is required for accurately describing compartmentalization of the beach and locating the aeolian sediment source areas in the Sand Motor domain.