Controls on the formation of potential landslide dams and dammed lakes in the Austrian Alps

Abstract

Abstract. Controls on landsliding have long been studied, but the potential for landslide-induced dam and lake formation has received less attention. Here, we model possible landslides and the formation of landslide dams and lakes in the Austrian Alps. We combine a slope criterion with a probabilistic approach to determine landslide release areas and volumes. We then simulate the progression and deposition of the landslides with a fluid dynamic model. We characterize the resulting landslide deposits with commonly used metrics, investigate their relation to glacial land-forming and tectonic units, and discuss the roles of the drainage system and valley shape. Modeled landslide dams and lakes cover a wide volume range and lake volume increases linearly with landslide volume in case of efficient damming, i.e. small landslides damming large lakes, which is in line with real-world inventories. The distribution and size of potential landslide dams and lakes depends strongly on local topographic relief. For a given landslide volume, lake size depends on drainage area and valley geometry. Largest lakes form in glacial troughs, while most efficient damming occurs where landslides block a gorge downstream of a wide valley, a situation preferentially encountered at the transition between two different tectonic units. Our results also contain inefficient damming events, a damming type that exhibits different scaling of landslide and lake metrics than efficient damming, and is hardly reported in inventories. We hypothesize that such events also occur in the real world and need documentation to better understand the effects of landsliding on the drainage system.