Multiproxy evaluation of the Paleohydrology of the Sakarya River during the Last Milennium, NW Anatolia

Paleohydrology studies are an emerging field of research linked to paleoclimatology and hazard estimation studies. Understanding the patterns of extreme events in the context of global change is of great importance, especially for regions where extreme events are an integral part of the hydrological regime, due to their social (e.g., vulnerability) and political (resilience and adaptation) implications. For many regions of the world where the instrumental record is very short and there are no historical records of hydrological events. These instrumental records can be extended by hundreds to thousands of years by reconstructing especially paleoflood events using fluvial archives.

We present the first detailed paleohydrology study in Anatolia. Our research focuses on the lower reaches of the Sakarya River at Adapazarı Basin, NW Anatolia, Türkiye. Here, the due unique tectonic setting controlled by the North Anatolian Fault, deposition of a 4.5-meter-thick fine-grained floodplain sediment since CE 1350 was possible. This timing constraint corresponds to the reign of the Ottoman Empire as well as to the Little Ice Age (LIA), an intermitted period(s) of cold and dry climate defined for the northern Europe. The characterization of past flow regimes of the river and the detailed identification of paleohydrology events within the studied section have been facilitated through a multidisciplinary and multi-proxy approach (grain size, mineralogy, geochemistry). All identified events have been precisely dated using age-depth model based on dendrochronology, radiocarbon, luminescence, and event-based dating techniques.

The focus sedimentary record revealed that the Sakarya River experienced distinct long-duration regular flow and drought episodes with intermittent flooding events for the last 600 years. Within this time frame, with intervals of uncertainty, three dry and three regular hydrological regimes have been identified from the year CE 1350 to 1950. Within these hydrological regimes, 9 periods of extreme drought and 10 flood events have been identified. These episodes are closely comparable with the published local and regional paleo-climatic record.