Swiss lakes are world-renowned for their rich archaeological heritage from the time of the pile dwellings, when Neolithic to Bronze Age people built their villages on stilts on the lake shores.

For the thousands of years that followed, people used Swiss lakes as trade routes. A precious aid for transporting goods, especially heavy or large objects. Blocks of stone extracted from the Jura quarries would have been difficult to carry on roads. Whether during the Gallo-Roman period, the Middle Ages, or the late periods, many ships did not reach their destination and sank to be quickly forgotten, buried under the sediments.

Ever changing lakes

In the 19th and 20th centuries, the Three Lakes region underwent profound changes (construction of reservoirs, canals, etc.) to stabilize water levels during floods or droughts. This constraint imposed on the lakes resulted in them beginning to reshape their beds, much like a diverted river. This erosion primarily affects coastal areas, with significant sand shifts, bringing to light archaeological remains such as Neolithic dugout canoes and 19th-century barges. A fragile catalogue of forgotten witnesses to our history.

Our recent underwater excavation project focuses on several shipwrecks which, due to their age and state of preservation, are invaluable sources for understanding the evolution of naval architecture and navigation in the Three Lakes region of Switzerland.

These remains were discovered during aerial prospecting flights. Fabien Langenegger, archaeologist at the office of heritage and archeology of the canton of Neuchâtel (OARC), is responsible for monitoring local underwater heritage. For many years, he has collaborated with the balloonist and engineer Fabien Droz to monitor the erosion fronts that endanger the prehistoric pile dwellings, but also to prospect the 30 kilometers of coastline the canton of Neuchâtel enjoys.

Wood has a voice

An anomaly spotted in 2015 allowed the discovery of a Gallo-Roman barge that is about two thousand years old. In 2017, a pile of large stone blocks led to the discovery of a second wreck, dated precisely to 1776 thanks to dendrochronology (a scientific method allowing the dating of pieces of wood by counting and measuring the tree rings). A third wreckage, which appears to have been intentionally sunk in the 16th century as the basis for building a signal, completes this trio of outstanding vestiges.

The rare barges that have been found in our lakes have almost all sunk with their cargo of limestone blocks, creating reliefs visible from the air. These boulders also helped stabilize the remains of the wreckage by keeping it at the bottom until silted up.

High scientific stakes

To date, only three Gallo-Roman wrecks have been identified and studied in Switzerland. In addition to the one discovered in the bay of Bevaix (NE) and presented in the navigation room of the Laténium Museum, a boat and a barge were excavated in Yverdon-les-Bains (VD) visible at the Yverdon Museum.

The “new” Gallo-Roman wreck discovered by Fabien Langenegger could prove to be historically important, as certain parts of the ship (such as one of its sides) could be very well preserved.

In the region of Trois-Lacs and Léman, there is a 1700-year gap to fill, between Roman boats dating from the 2nd century AD. and the many 19th century boats that were found. The study of the remains of the 16th and 18th century boats may therefore be paramount to better understanding the evolution of shipbuilding on our lakes.

Short-term threats

Located at a shallow depth and protected by a thin layer of sediment, the three wrecks are now vulnerable, as they are located in a part of the lake particularly exposed to the prevailing winds.

Les blocs de calcaire étaient taillés dans le jura, puis acheminés jusqu'au port pour être chargés sur les challands © Octopus Foundation

For this first lake heritage preservation project, the Octopus Foundation will provide a team made up of five qualified divers and two aerial and submarine drone pilots. This field team will assist the archaeologists in their excavation project and informs the public on this rich topic.

In exchange, the OARC allows the Octopus Foundation to acquire knowledge of underwater archaeological excavation techniques in cold water and to publicize the excavations on its own behalf and on behalf of the OARC. The first campaign took place in April 2019 and allowed for the complete excavation and documentation of the 18th-century shipwreck.

Thanks to underwater 3D models, the objective is to keep track of each step of the underwater excavations.

The Octopus Foundation was thrilled to be able to work almost “at home”, in particular for the study and preservation of wrecks threatened by underwater erosion.

In November 2018, a scouting mission brought together Fabien Langenegger and the Octopus Foundation diving team to collect all the data necessary for the preparation of the project. During this short three-day mission, it was also possible to dive on the wreck of the Quai Osterwald in Neuchâtel. This ship, which sank in 1853, is 30 meters long and lies between seven and eight meters deep. In one dive, the team was able to deploy the underwater markup and make a photogrammetric acquisition of nearly 600 photos. The 3D model of this magnificent wreck is available here.

Aerial drones

The use of aerial drones is particularly useful for detecting underwater objects when they are at shallow depth and in clear water.

By flying several tens of meters above the surface, the pilot may spot the wrecks and pin them on a map. The drone can thus scan certain areas which will then have to be excavated by the underwater archaeologists.

For this project, the use of several drones with different optics will help archaeologists collect valuable data on these wrecks.

Underwater drone (ROV)

Using the OpenRov Trident may help us to:
– preview a wreck before sending a team of divers
– perform photogrammetry and 3D modeling of submerged sites
– capture images at depths and in areas difficult to access by divers
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3D models of wrecks

Once the underwater photographic acquisition has been completed, the Octopus Foundation processes the data to obtain a 3D modeled area like the ones below.

By clicking on the symbol in the center of the window, once the model is loaded, you can rotate the area by clicking in the center and moving the cursor. You can also zoom and move the model by holding down the shift key.

These simple and free tools provided by the Octopus Foundation allow people with little or no diving experience to explore the depths of the lakes and seas, and study various archaeological pieces with no risk of damage.

Photogrammetry

Whether for the public or diving enthusiasts, these digital models are effective visualization tools. But are they also useful for scientists? We keep in mind that one of the first objectives of the Octopus Foundation is to support research and scientific exploration of the oceans.

From the digital 3D model, a simple visualization element, the computer program makes it possible to extract a scientific tool: the orthophotoplan. By a vertical projection of the entire relief on a horizontal plane, this centimeter-accurate map respects all dimensions on the ground. While diving time is limited by the air contained in a tank, it is now possible to extract the archeological site out of the water to allow it to be studied carefully on land.

The 18th-century barge

This mission revealed an exceptionally well-preserved vessel, 15 meters long and nearly four meters wide, carrying approximately sixty finely carved blocks of Hauterive limestone. Excavations showed that the cargo was very likely too large for the size of the boat (estimated at around 15 tons) and that a gust of wind midway between the Neuchâtel shore and the Broye Canal likely caused it to sink. Several objects of interest, including a hammer (found between the frames), a mooring chain with its hook, and a belt buckle, were discovered and are now protected by the OARC (Neuchâtel Cantonal Archaeology Office). This discovery, made possible by the fieldwork of the Octopus Foundation, will allow Fabien Langenegger to fill an important gap, since no shipwreck dating from the period between the Gallo-Roman era and the 19th century has ever been discovered in such a state of preservation.

Dendrochronological analysis of several pieces of wood used in the boat’s construction places it around 1771. This date is a terminus postquem, meaning that the last growth ring found on the planks corresponds to 1771, making it impossible for the trees to have been felled before that year. However, it is possible that some rings are missing after this date; rings that could have been lost during the sawing process, for example. The boat was therefore probably built between 1771 and 1780.

The stone blocks, averaging one meter in length and 30-40 cm in width and height, were almost certainly intended for a manor house or port infrastructure such as a quay.

This barge must have loaded its heavy cargo at a quay in Hauterive and was likely destined for the Estavayer or Murten area. It was found almost exactly on the straight stretch between Hauterive and the entrance to the Broye Canal, which leads to Lake Murten.

Miraculously preserved, the boat is intact, its sides crushed by the pressure of the limestone blocks that collapsed on either side during what must have been a violent shipwreck. The vast majority of the boat’s structural elements are pegged together. Among the few metal pieces recovered is a long piece that served to secure the shrouds, the ropes that held the mast on either side of the vessel.