Chapter 14: The Sand Spits of the Rhône River Delta: Formation, Dynamics, Sediment Budgets and Management

Abstract

This chapter describes the morphology and dynamics of the three sand spits flanking the Rhône river delta: Gracieuse, Beauduc and Espiguette spits. The formation and distal extension of these spits (respectively +5, +10–15, +10–15 m/ year) results from active wave-induced longshore transport that generates sand migration downdrift from erosional updrift sectors. These erosional sectors are systematically associated with former delta distributary mouths that are being reworked by waves. In other words, the sand brought down to the sea by the Rhône participates in the construction of sand spits only following mouth abandonment. Finally, as a result of the curvature of these spits, the overall aeolian regime induces sand migration seaward in the southern sectors of the spits near the transition zone between eroding and accreting sectors. Understanding these functional aspects of spit formation and growth is important in terms of management of the Rhône delta shoreline and its sediment budget by public authorities.