Abstract
Cheniers are ridges consisting of coarse-grained sediments, resting on
top of the fine sediment that forms the otherwise muddy coast. In this
paper, we use Delft3D to explore how cheniers are formed through wave
winnowing. We identify three phases of chenier development: (1) a
winnowing phase, during which mud is washed out of the seabed initially
consisting of a mixture of sand and mud, (2) a sand transport phase,
when the sand in the upper layer is transported onshore, and (3) a crest
formation phase, during which a chenier crest rapidly develops at the
landward limit of onshore sediment transport. The main mechanism driving
onshore sand transport is wave asymmetry. During calm conditions, sand
transport takes place within a narrow band limiting the volume of sand
delivered nearshore, and therefore no chenier develops. In contrast,
average storm conditions mobilise sufficient sand for a crest to
develop. Our results thus reveal that chenier formation through wave
winnowing does not require extreme storm conditions. Furthermore, our
study showed that chenier formation through wave winnowing is a
relatively slow process, with the largest time scales associated with
the winnowing and sand transport. Once sufficient sand is available
nearshore, the crest develops rapidly.