Glaciological Investigations at Glacier du Giétro and Glacier de Corbassière
Bauder, Andreas Funk, Martin
Glacier de Corbassière with a length of 9.8 km and an area of 18.2 km2 is one of the largest glacier in the Swiss alps. The steep tongue of Glacier de Giétro (4.3 km long, covering an area of about 5.5 km2) flows over cascades and ends today 500 m above the bottom of the main valley. During the general glacier maxima of the Little Ice Age at the end of the 16th and beginning of the 19th century, the glacier advanced over steep valley sides.
The river in the main valley was occasionally dammed by accumulated ice blocks after break-offs. In 1595 and 1818 large water outbursts started catastrophic splash floods causing large damage down to the Rhone valley. Since the construction of the Mauvoisin reservoir in 1957 break-offs of large ice masses may cause an oversplash over the dam at times when the reservoir is nearly filled. The safety of the installation is of main interest and requires a continuous supervision.
The glaciers have been monitored intensively since the 1960's. Measurements of mass balance, flow movement, and volume changes document the general variations of the glaciers. Automatic observation systems have been developed in order to measure the surface displacement continuously and detect short-term changes of flow behaviour. Over more than 2 decades a total station (motorized theodolite with distance meter) that automatically follows several moving targets was operated by a telemetric data transmission. This system has recently been replaced by time-lapse photography allowing the monitoring of both ice flow and structures at surface over a larger area.
Bauder, A. (2003): Automatic surveying for hazard prevention on Glacier de Giétro, In Milestones in Physical Glaciology From the Pioneers to a Modern Science, International Glaciological Symposium held in honor of Prof. Dr. Hans Röthlisberger on the occasion of his eightieth birthday 14. February 2003. Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie der ETH Zürich, Mitteilungen 180, 1-3
There are several larger glaciers situated in the Mattmark area among them Allalingletscher, Hohlaubgletscher and Schwarzberggletscher. Since the beginning of the 20. century the Mattmark area and the glaciers have been focus of continuous hydrological and glaciological investigations. Several long-term data sets exist on precipitation, ice volume change, glacier mass balance and ice flow speed. Fluctuations of Allalingletscher repeatedly interfered human activity in the valley. During Little Ice Age the terminus dammed the river Saaser Vispa forming a lake. Occasional drainage of the ice dammed lake several caused times serious damages in the Saaser valley. During the construction of the Mattmark reservoir in 1965 an ice avalanche from a large break-off at the terminus destroyed the construction site an killed 88 people.
In order to support the local hydro power company managing the energy production, a glacio-hydrological monitoring program is conducted. The evolution of the glacier terminus of the glaciers Allalin, Chessjen, Hohlaub, Schwarzberg and Seewjinen is documented annually. Measurements of ice flow and mass balance are registered at selected locations. The photogrammetrical analysis of the surface topography in regular intervals allows the determination of ice volume change. Lastely, the seasonal evolution of the glacier terminus and in the forefield of Allalingletscher is monitored with daily time-lapse photography.
The available data base on glacier fluctuations in the catchment is worldwide unique. It allows the evaluation of the effects of climate change on glacier melt and runoff production. With the expected substantial future glacier retreat, the runoff characteristics in the catchment will be severly altered. The hydropower production relys on winter accumulation and summer melt at present. Adaptive measures will be necessary for the management in the future. The well documeted gradual changes of the state of the glaciers allow to adapt well in advance.