Erosion threatens Zurich Lake’s prehistoric pile dwellings

The prehistoric pile dwellings in Lake Zurich are at risk of decay as erosion removes the sediment that protects them, SRF reports. Ship propellers, construction work and changed currents are exposing the fragile wooden remains.

About 70 pile-dwelling sites have been documented in Lake Zurich. The remains of prehistoric settlements built on wooden posts along the shores provide insights into how people lived around 5,000 years ago, before written records existed.

The settlements survived because layers of sediment on the lakebed protected them from oxygen. Most microorganisms that break down organic matter need oxygen, so decomposition is greatly slowed or stopped without it. Plant remains, including pollen and grains, have also been preserved, revealing what people grew and ate.

Today, the lake is used for swimming, diving, boating, fishing and construction. These activities alter water currents and expose the archaeological remains. Once the protective sediment has been removed, the wooden structures can rot within a few decades, says Andreas Mäder, head of Zurich underwater archaeology.

Staff from Zurich underwater archaeology are working at a site off Feldmeilen, recovering and documenting exposed artefacts. They are precisely measuring and mapping the wooden foundations of the pile dwellings.

The remains can then be protected by covering a section with fleece and adding a layer of gravel. A site off Feldmeilen is due to be covered in this way within one or two years. Gravel was also placed over a site in Lake Hallwil in 2017 to protect the pile dwellings and preserve them for future research.