We investigate four study areas in different mountainous regions of the world to develop our methods and to evaluate and demonstrate their applicability and transferability. The study areas have a wide range of tectonic, climatic and lithological settings which makes them ideally suited to extensively test our techniques.
The European Alps have a high population density and a long tradition in research compared to other mountain ranges. Therefore, landslide hazard and risk assessment are well established and a number of regional and national landslide inventories have developed and make the European Alps a suitable region for method testing and validation. In addition, extensive historical records provide a basis for linking landslide magnitude and frequency to recent climate change – an aspect that is of great importance for modulating temporal hotspots of landslide dam initiation as well.
Southern Alps of New Zealand:
The Southern Alps of New Zealand are the surface expression of an on-going oblique collision of the Australian and Pacific plates and serve as a test site due to the unique tectonic and climatic setting – a wide range of rock uplift rates within which some locations experienced substantial glaciation whereas others remained ice free. In addition, this study area features an enormous gradient in precipitation rates from 12,000 mm a-1 to 800 mm a-1. While landslides are a key factor of orogen evolution in the high-uplift and high-precipitation regions, they have almost fully eradicated glacial imprint within the current interglacial. In addition, active continental collision makes the New Zealand Alps an earthquake hotspot.
The mountains of Taiwan, which are subjected to frequent earthquakes, are situated in the active subduction-collision region between the Eurasian Continent and the Philippine Sea plates and among the fastest uplifting mountain ranges worldwide. They are located in a subtropical/tropical climate and remained ice-free during most of the Pleistocene. About 70 % of the island is mountainous with 286 summits over 3,000 m a.s.l. The topography is characterized by fractured rock formations, high relief and steep stream gradients. Taiwan is located on the major tracks of typhoons (tropical cyclones) and experiences, on average, four to five typhoons per year. These facts make Taiwan highly susceptible to landslides, which regularly lead to fatalities and severe damage to infrastructure. The Taiwanese mountain landscape is, at least in part, densely populated and human lives and infrastructure are frequently affected by large landslides and landslide-river interference.
Himalayas of Nepal:
Northern Nepal is subject to rapid uplift and exhumation as well, was repeatedly glaciated during the Pleistocene and hosts some of the highest peaks and rock faces worldwide. The entire study region was repeatedly affected by large earthquakes, the last of which took place in May 2015 and caused more than 4,000 landslides.