Yvonne Schaub

Landslides and New Lakes in Deglaciating Areas: A Risk Management Framework

New lakes forming in high-mountain areas due to climate-driven glacier shrinkage are likely to be located in areas of potentially unstable slopes. Therefore they are prone to impacts from rock/ice-avalanches and other types of landslides, which might trigger outburst floods causing damage farther down valley. In view of an integral lake management, a risk management concept for the Swiss Alps is proposed in this study, which consists of risk analysis, risk evaluation and the integral planning of risk reduction measures. The pertinent question is how risk, resulting from natural hazard process chains involved with landslides and new lakes, can be assessed. The present knowledge basis together with currently available models, methods and tools is herein reviewed. Knowledge gaps are mainly identified in the determination of future landslide detachement zones and in the evaluation of changes in landuse and damage potential.

Limits and challenges to compiling and developing a database of glacial lake outburst floods

A unified database of glacial lake outburst floods (GLOFs) has been created for analysis and future natural hazard evaluations. The data from individual case studies fill the database at a primary level, while the regional and global scales are more suitable for evaluating the information. There is enhanced research activity in this topic worldwide due to ongoing environmental changes, and this is apparent in the database. Database compilation is linked to the International Programme on Landslides (IPL) because different types of slope movements are the most common triggering factors for glacial lake outburst floods, and the outburst floods, on the other hand, often initiate different types of slope movements.

New lakes in deglaciating high-mountain regions – opportunities and risks

In connection with the ongoing disappearance of glaciers in cold mountains, a great number of new lakes come into existence. The sites and approximate formation time of such potential new lakes can be realistically modelled. This provides an important knowledge base for planning the management of at least the larger ones among such lakes. New water bodies can markedly increase the hazard and risk potential for down-valley areas in the long term, especially in relation to impact/flood waves triggered by rock/ice avalanches from the steep icy peaks surrounding them. However, they also offer opportunities for use in connection with tourism, water supply and hydropower production. Legal regulations and aspects of landscape protection and nature conservation have to be thereby carefully considered. Possible synergies and conflicts exist; they can be anticipated at an early stage by a matrix-type analysis of interrelations between the different perspectives involved. A corresponding inter- and transdisciplinary study was performed for the currently glacierized areas of the Swiss Alps. The results of this study may serve as an example for dealing with the consequences of rapid climate-induced changes in other populated regions with rugged icy mountains, such as the Peruvian Cordilleras or the Himalaya-Karakoram region.

Ice-avalanche scenario elaboration and uncertainty propagation in numerical simulation of rock-/ice-avalanche-induced impact waves at Mount Hualcán and Lake 513, Peru

The interest in numerical simulation of cascading processes involving mass movements and lakes has recently risen strongly, especially as the formation of new lakes in high-mountain areas as a consequence of glacier recession can be observed all over the world. These lakes are often located close to potentially unstable slopes and therewith prone to impacts from mass movements, which may cause the lake to burst out and endanger settlements further downvalley. The need for hazard assessment of such cascading processes is continuously rising, which demands methodological development of coupled numerical simulations. Our study takes up on the need for systematic analysis of the effect of assumptions taken in the simulation of the process chain and the propagation of the corresponding uncertainties on the simulation results. We complemented the research of Adv Geosci 35:145-155, 2014 carried out at Lake 513 in the Cordillera Blanca, Peru, by focusing on the aspects of (a) ice-avalanche scenario development and of (b) analysis of uncertainty propagation in the coupled numerical simulation of the process chain of an impact wave triggered by a rock/ice avalanche. The analysis of variance of the dimension of the overtopping wave was based on 54 coupled simulation runs, applying RAMMS and IBER for simulation of the ice avalanche and the impact wave, respectively. The results indicate (a) location and magnitude of potential ice-avalanche events, and further showed (b) that the momentum transfer between an avalanche and the impact wave seems to be reliably representable in coupled numerical simulations. The assessed parameters—initial avalanche volume, friction calibration, mass entrainment and transformation of the data between the models—was decisive of whether the wave overtopped or not. The overtopping time and height directly characterize the overtopping wave, while the overtopping volume and the discharge describe the overtopping hydrograph as a consequence of the run-up rather than the wave. The largest uncertainties inherent in the simulation of the impact wave emerge from avalanche-scenario definition rather than from coupling of the models. These findings are of relevance also to subsequent outburst flow simulation and contribute to advance numerical simulation of the entire process chain, which might also be applied to mass movements other than rock/ice avalanches.

Current and Future Glacial Lake Outburst Flood Hazard: Application of GIS-Based Modeling in Himachal Pradesh, India

Most studies concerning the hazard from glacial lake outburst floods have focused on the threat from lakes that have formed over the past century, some of which have demonstrated significant growth in response to recent warming of the climate system. However, attention is shifting toward the anticipation of future hazard and risk associated with new lakes that will develop as glaciers continue to retreat and water accumulates within depressions in the exposed bed topography. Using the Indian Himalayan state of Himachal Pradesh as a case study, this chapter provides both a review and implementation of modern approaches to assess current and future glacier lake outburst flood hazard over large spatial scales. Across Himachal Pradesh, the formation of new lakes over the next decades will lead to a minimum two- to threefold increase in land area affected by potential lake outburst floods in several districts. Generally the potential increase in glacial lake outburst flood frequency is demonstrated to be even greater, owing to the heightened opportunity for ice or rock avalanches to impact into larger and more numerous glacial lakes. Methods described herein allow early anticipation of future threats, providing a scientific basis for sound adaptation and planning responses.