Rapid headward erosion of marsh creeks in response to relative sea level rise

Abstract

Tidal creeks in Cape Romain, South Carolina, are extending rapidly onto the established marsh platform producing an unusual morphology, which remains self‐similar in time. A time‐series of aerial photographs establishes that these channels are headward eroding at an approximate rate of 1.9 m/yr. The rapid rate of headward erosion suggests that the marsh platform is in disequilibrium and unable to keep pace with high local relative sea level rise (RSLR >3.2mm/yr) through accretionary processes. Biological feedbacks play a strong role in the morphological development of the creeks. Dieback of vegetation coupled with intense burrowing by crabs produces a bare and topographically depressed region beyond the channel head toward which the channel head extends. We examine the mechanisms producing this headward extension and pinnate channel morphology, and report a new pattern of creek incision in a regime of rapid RSLR.