Aubrey, D.G. and A.G. Gaines Jr.
Marine Geology, Vol. 49, pp. 257-278, 1982 WHOI-R-82-018
Three possible mechanisms cause barrier spits to elongate; two are generally known, while a third is presented in this paper. The most commonly cited mechanism for spit elongation, according to the authors, is downdrift buildup on the tip of a barrier spit from sand introduced by longshore transport. A second mechanism is accretion on the end of a barrier spit bordering a tidal inlet; this is generally accompanied by erosion of the spit on the opposite side of the inlet. A third mechanism, proposed in this paper, is self-generative in the sense that it does not require an external sediment source to elongate a barrier spit (although an external source could accelerate the process). This mechanism operates under a restrictive set of conditions, so it is not as common an occurrence as the mechanisms mentioned above. The paper discusses a prototype (Popponesset Beach, MA) used by the authors to illustrate this mechanism and describes, in detail, this unconventional method for increasing barrier spit length. The authors also suggest that, based on this third mechanism, estimates of directions and rates of longshore sand transport based on spit development must be scrutinized on a case-by-case basis.