Human-induced reactivation of a dormant earthflow? A geomorphological interpretation of historical mining maps of the Ischl salt mine (Austria)

This case study from the Northern Calcareous Alps demonstrates the utilization of historical mining documents for geomorphological purposes, especially for landslide event documentation. The combination of geomorphological mapping and interpretation of up to 200 years old mining maps of the Ischl salt mine (Austria) revealed the existence of a 500 m long earthflow in an engineering geologically well-investigated area. The CAD-based creation of a polythematic map (surface and subsurface features) led to the conclusion that a prehistoric earthflow has been partly reactivated between 1850 and 1934 due to mining subsidence. The depletion zone of the historical earthflow is situated directly above the major collapse zone of the mine. Reactivation was most likely caused by the lowering of the slope base due to slow development of a subsidence trough within the ductile Haselgebirge Formation. Particularly for engineering geomorphological tasks in post-mining-areas, where subsurface facilities are no longer accessible, a combined approach of historical mining map analysis and geomorphological mapping can be regarded as a promising and cost-effective working concept. Supplementary material: historical ground plans and cross sections which are listed in Tab. 1 are available at: https://doi.org/10.6084/m9.figshare.21740459.v1 Thematic collection: This article is part of the Engineering Geology and Hydrogeology of the Anthropocene collection available at: https://www.lyellcollection.org/topic/collections/engineering-geology-and-hydrogeology-of-the-anthropocene