Using historical data to access the surface subsidence in the vegetable belt of the Three Lakes Region, Switzerland

Abstract

AbstractThe ‘Grosses Moos’ in the Three Lakes Region (Berner Seeland) was formed by the Wallis glacier resulting in a peat bog-dominated landscape. During the last two centuries this area was drained by a complex channel system to enable highly fertile agricultural activity. As such, the region is the vegetable belt of Switzerland. However, as the peat has degraded due to overexploitation, the situation for agriculture production has become critical. Consequently, measures are needed to prevent soil degradation and water accumulation. The extent of surface changes for the last ~ 100 years is, however, not precisely known and is assumed to have varied spatially. To understand the historical evolution of this area, we used a unique map from 1920 to compare the surface height with the newest digital terrain models (DTM) in order to estimate surface subsidence, and thus soil degradation, for the last 100 years. More than 44,000 single measurement points drawn on the historical map were digitized to derive the DTM that served as a basis for further analysis. The in-depth investigation of the observation methods and the accuracy assessment allows us to conclude that differences in the DTMs of up to 2.4 m (i.e., averaged rate of 2.4 cm yr−1) can be attributed to large-scale soil subsidence and that degradation was heterogeneously distributed over the investigated area. The data provide the basis for further soil restoration efforts in the area.