Evolution of ancient harbours in deltaic contexts: A geoarchaeological typology

In deltaic areas, within a context of relative sea-level stability during the past 6000 years, environmental conditions have been key in mediating human settlements and the evolution of ancient harbours. The natural diversity of clastic-coast environments, in particular deltas, is central to explain the wide disparity in harbour contexts. It is, therefore, important to understand the impact of these settlements on the evolution of clastic coasts. How did ancient societies exploit and adapt to deltaic environments? Here, we detail a typology of ancient harbours on clastic coasts using a suite of multidisciplinary case studies from the Mediterranean and the Black Sea. We present the impact of different forcing agents (floods, storms, sedimentary inputs, relative sea-level (RSL) changes, dredging and harbour structures) on the geomorphological evolution of selected harbour sites, and underline the important role of coastal changes at different temporal and spatial scales. These processes affected the infrastructure and the viability of harbours to varying degrees. In deltaic contexts, our analysis differentiates five harbour types: (1) fluvial harbours, affected by floods, rapid sedimentation and river-channel changes; (2a) infilled estuarine harbours; or (2b) submerged estuarine harbours, lying at the interface between marine and fluvial processes; (3) lagoonal harbours strongly affected by sedimentary inputs; and (4) the impact of humans on harbour basins via harbour protection structures and dredging. For these harbour types, we probe the advantages and disadvantages of each geomorphological setting, in addition to the consequences of environmental pressures on human societies.