Marginal deltaic coasts in transition: From natural to anthropogenic along the southern Romanian cliffed coast

Abstract

In natural conditions marginal deltaic coasts benefit from sediment input from upcoast deltas via longshore drift and current-driven transport. This study investigated changes in the pattern and variability of both the shoreline and nearshore zone along the southern Romanian coast located downdrift of the Danube delta. We employed modern and historical cartographic materials to compare the baseline behavior before and after large coastal engineering works were emplaced in the last half century. From the early 20th century until 1960, the shoreline was largely progradational and the nearshore depositional indicating that the coast had a positive sediment budget. After 1960, and especially after 1980, a general erosional state took over the region as the jetties of the expanding Constanta and Midia Port increasingly blocked the bulk of the southward-directed Danubian longshore drift. Further development of ports and seaside resorts also led to a less coherent, fragmented coastal dynamics masking any potential effects of far-field anthropogenic changes in the Danube delta from reduced fluvial discharge or changes in longshore drift. The beach protection structures in seaside resorts did not successfully address the general state of sediment starvation. We conclude that the southern Romanian shore cannot provide a good example for protecting other marginal deltaic coasts with sensitive sediment budgets. An interactive map created in this study provides a starting point for future work to better understand the link between deltas and major ports connected with them.