7000-year-old ancient seawall in Israel puzzles archaeologists though it failed to stem sea level rise

7,000-year-old seawall in Tel Hreiz in Israel reveals earliest known structure built against sea level rise that remains a challenge even to this day

Photographs of finds from the Tel Hreiz settlement: (a-b) exposure of stone-built features in shallow water. (c) wooden posts dug into the seabed. (d) bifacial flintadze. (e) in situ stone bowl made of sandstone. (f) in situ basalt grounding stone (scale = 20cm); (g) burial 1. (h) suspected stone-built cist grave - view from the east (scale = 20cm). (i) in situ antler of Mesopotamian fallow deer, Dama dama mesopotamica. E. Galili / V. Eshed

Almost 7,000 years ago, during the Neolithic period, these ancient villagers in Israel had built a seawall on the Carmel Coast to protect their settlement against rising sea levels in the Mediterranean, thought to be the first battle against against rising oceans.

A team of researchers from the University of Haifa, Flinders University in Australia, the Israel Antiquities Authority and the Hebrew University found the oldest known coastal defence system ever uncovered anywhere in the world, that too constructed by ancient settlers about one to 2 kilometers near their village.

100-meter-long ancient seawall

In a study published in PLOS ONE, Ehud Galili from the Zinman Institute of Archaeology, University of Haifa, said that the 100-meter-long seawall proved to be a temporary reprieve and the ancient village was eventually abandoned and inundated, leaving behind the traces of how humanity fought the threats posed by sea level rise, that remains a challenge even to this day.

Isometric modelling of the Tel Hreiz seawall based on an aerial photograph of the site and its hinterland (b) schematic cross section of the site today (c) during the Pottery Neolithic period J. McCarthy, E. Galili, and J. Benjamin

"During the Neolithic, Mediterranean populations would have experienced a sea-level rise of 4 to 7 mm a year or approximately 12-21cm during a lifetime (up to 70 cm in a 100 years). This rate of sea-level rise means the frequency of destructive storms damaging the village would have risen significantly," says Dr Galili.

Ancient response to sea level rise

Since the accumulating yearly sea-level necessitated action, these people would have responded by constructing the coastal protection wall similar to what we're seeing around the world now, say at the Indonesian sinking capital of Jakarta today. In fact, Tel Hreiz was built at a safe elevation of up to 3 metres above sea level but post glacial sea-level rises of up to 7mm a year, thus threatening their settlements.

Carmel coast
Eastern Mediterranean and the Israeli coast: Submerged Neolithic settlements off the Carmel coast 2019. John McCarthy after Galili et al

The Tel Hreiz settlement was first categorized as a potential archaeological site in the 1960's but the revelations in 2012 have started providing some previously unknown archaeological material as there are no known similarly built structures at any of the other submerged villages in the region. The Tel Hreiz site is a unique example of this "visible evidence for human response to sea-level rise in the Neolithic," says co-author Dr Jonathan Benjamin from Flinders University in Australia.

ancient village and seawall
Artist reconstruction of ancient village and seawall. John McCarthy and Ehud Gallili

Moving to the current 21st century, sea level rise is in the range of 1.7 to 3 mm per year, representing a smaller change when compared to the threat experienced by the Neolithic community that built the ancient sea wall. But the challenges remain the same, said the authors of the study.