UZH researchers prove subsidence of the Great Marsh

Zurich/Bern – Researchers at the University of Zurich (UZH) have documented the subsidence of the Great Marsh in the Bernese Seeland using digital mapping. Compared to 1920, the terrain has sunk up to 2.40 meters in some places. The measurements provide information about necessary soil remediation.

Researchers from the Institute of Geography at the University of Zurich (UZH) have used digital measurement protocols to discover that the ground of the Great Marsh in the Bernese Seeland has subsided by 2.40 meters over the past 100 years. According to a press release, the team led by Markus Egli and Claudia Röösli compared manually collected data from a historical terrain survey with new data from a digital terrain model created by the Federal Office of Topography.

The first step was to digitize the 44,000 survey points on the map of the area, which was produced manually in 1920. The data obtained in this way was compared with current terrain data, including that obtained terrestrially using LiDAR or from aircraft. LiDAR is a measurement system based on laser technology. A comparison of the historical data set with the current data set shows not only that the Bernese Seeland has subsided overall, but also where the greatest subsidence has occurred.

The researchers believe that one of the main reasons for the subsidence of the peat soil is the extensive agricultural use of the area, which is also known as Switzerland's vegetable garden. This was accompanied by intensive drainage of the terrain with the consequences that have now been observed. The maps of the Great Marsh created by the UZH researchers show where soil remediation will be necessary in the foreseeable future and where a switch should be made to sustainable, environmentally friendly agriculture. ce/ww

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