Barrier-fronted saltponds (Cape Cod, USA) and limans (NW Black Sea, Ukraine): Comparative morphostratigraphy and response to sea-level rise

Abstract

Microtidal saltponds of the upper Cape Cod (MA, USA) and the limans of the non-tidal northwestern Black Sea are compared on the basis of their planimetric and barrier-stratigraphic characteristics. The shore-normal ellipticity value (en) is defined as a means of distinguishing between shore-normal (valley-type) and shore-parallel (lagoon-type) trending water bodies, in addition to quantifying their overall morphology. Besides the differences in morphological response to relative sea-level rise of the bays with different en values (greater impact of barrier retreat on bays with lower en), the size of the water bodies and barrier width and height are important factors in determining their response. Given simple landward barrier translation, an average liman with en=−0.8 will have a 50% reduction in open-water area over approximately 1000 years, whereas less than 10% decrease is predicted for valley-type systems (en=0.8) over the same time interval. Similar retreat will take place in just 300 years for saltponds. Although relative sea level is rising at a slower rate along the south shore of Cape Cod than along NW Black Sea, it is expected to have a greater impact on saltpond water area reduction due to their smaller sizes and narrower barriers. Engineering structures make it difficult to predict the near-future behavior of individual coastal segments. Storm-driven flooding, overwash, and breaching of narrow and low barrier segments will be the likely morphodynamic response at both sites.