NEW LAKES IN DE-GLACIATING HIGH-MOUNTAIN REGIONS – A CHALLENGE FOR INTEGRATIVE RESEARCH ABOUT RISK REDUCTION AND SUSTAINABLE USE

Wilfried Haeberli, Christian Huggel, Yvonne Schaub, Geography Department University of Zurich

Foro Intercaional Glaciares

vanishing surface ice

de-buttressing of lateral rock slopes oversteepened

inside slope of lateral moraine

disappearing support of steep glacier parts, ice avalanches from steep hanging glaciers

ice avalanches and rock falls not on glacier tongue any more but directly into lake

permafrost degradation slope instability

Milhuacocha Cordillera Blanca Hegglin

lake formation

Foro Intercaional Glaciares

Changing high-mountain glaciers

Paul

Cordillera Blanca

Aletsch, Alps

Assumption: temperature increase of 4°C by 2100, time steps of 15 years

Scenario of glacier retreat and lake formation Swiss Alps (Aletsch)

Aletsch Swiss Alps Schaub

Glaciers, new lakes, permafrost and steep slopes in the Alps

Foro Intercaional Glaciares

Portocarrero 12.04.2010

A successfully prevented catastrophe

Nevado Hualcán Cordillera Blanca Portocarrero

Foro Intercaional Glaciares

Palcacocha, Peru

Modeling the process chain and installation of an early warning system …

Nevado Hualcán Cordillera Blanca Schneider

Foro Intercaional Glaciares

Lake probably shallow

Lake probably deep

Lake formation uncertain

Lake formation ongoing or imminent

Lake formation in coming decades

possible retention

Hazard evolution Carhuaz

Terrier

Terrier

Künzler

Hydropower and flood protection Corbassiière Swiss Alps

Foro Intercaional Glaciares

The long-term risks of destructive flood waves from new lakes in deglaciating high-mountain regions are increasing …

… and need risk reduction strategies to be developed in time

because • the number of new lakes increases with continued glacier retreat • the new lakes are forming more and more closely to steep icy rock walls • the stability of these steep icy rock walls tends to decrease • the probability of large ice/rock avalanches into lakes increases • impact waves in new lakes from slope instability become more frequent • corresponding flood waves can affect valleys over long distances • the hazard zone related to rock/ice avalanches is thereby extended • areas of high vulnerability/damage potential may be affected • the probability of dangerous events and the damage potential both grow

by • modelling potential new lakes and critical slope conditions • modelling potential process chains to delineate hazard zones • defining hot spots of highest vulnerability • using existing experience/practice of protection against impact waves • considering aspects of long-term low probability/high damage risks • envisaging possible synergies with hydropower, water supply, tourism