Showing papers by "Wilfried Haeberli published in 1983"

Frequency and Characteristics of Glacier Floods in the Swiss Alps

Abstract: Damage due to glacier floods in the Swiss Alps occurs about once every two years at present, despite the pronounced retreat of glaciers during the twentieth century and the installation of many water reservoirs, which act as flood retention basins. Over half (60 to 70%) of the observed floods are caused by outbursts of marginal glacier lakes or sudden breaks of ice dams, and 30 to 40% by ruptures of water pockets. In a glacierized mountain region as densely populated as the Swiss Alps, even debris flows triggered by outbursts of very small water masses may be dangerous. Historical information about glacier floods in the Swiss Alps, although incomplete and heterogeneous, is used as an empirical basis for an attempt to recognize potential hazards at an early stage by considering outburst processes, volumes of water involved, potential peak-discharge values, lithology and inclination within the reach of glacier streams.

Accumulation characteristics on a cold high-alpine firn saddle from a snow-pit study on Colle Gnifetti. Monte Rosa, Swiss Alps

Abstract: Diverses caracteristiques de la neige, isotopes (δ 18 O, 3 H), conductivite electrique, poussieres, trace d'elements et pollen ont ete etudies dans une tranchee englobant environ deux ans et demi d'accumulation neigeuse afin de determiner une «clef» pour l'interpretation stratigraphique des carottages dans les regions de neves froids en haute-montagne sur le Colle Gnifetti (4 450 m s.m., Mont Rose). On observe que la forte influence du vent mene a des phenomenes de melange et de resedimentation des couches superficielles. Toutefois, sur la base de l'information tiree de la combinaison des differents parametres observes, il est possible de dater une grande part des couches de neige et parfois d'en determiner l'origine. En plus des horizons de glace, qui n'apparaissent que dans les couches estivales, des indices marquants sont les poussieres sahariennes, caracterisees par la pointe de teneur en poussiere et de conductivite

Snow accumulation, firn temperature and solar radiation in the area of the Colle Gnifetti core drilling site (Monte Rosa, Swiss Alps): distribution patterns and interrelationships

Abstract: Distributional patterns of glaciological parameters at the Colle Gnifetti core drilling site are described and their interrelationships are brietly discussed. Observations within a stake network established in 1980 furnish information about snow accumulation (short term balance), submergence velocity of ice flow (long term balance), ram hardness (melt layer stratigraphy), and firn temperature. In addition, a numerical model was used to estimate local variations of available radiant energy. Melt layer formation is considerably more intensive on the south facing parts of the firn saddle where incoming radiation is high. These melt layers seem to effectively protect some of the fallen snow from wind erosion. As a result, balance ist up to one order of magnitude larger on south facing slopes. Heat applied to the surface is therefore positively correlated with balance, whereas the relation between solar radiation and firn temperature is less clear. Distributional patterns of submergence velocity confirm that the observed spatial variability of surface balance is representative for longer time periods and greatly influences the time scale and the stratigraphy of firn and ice cores from Colle Gnifetti.