Glacial lakes

Glaciers and the surrounding areas, as has been evident in particular in recent decades, constitute a rapidly changing environment strongly affected by climate change. The formation of glacial lakes is often associated with this evolution, the origin of which is deeply linked to glacial dynamics and morphologies of the territory. In the current climatic phase, characterized by a marked reduction in glacial masses and accelerated melting processes, the formation of glacial lakes is a process that occurs with increasing frequency.

More in detail, according to their location, these lakes can be defined as: periglacial (present in the areas surrounding the glacier, in contact with it or not), proglacial (in front of the glacier), epiglacial (above the glacier surface) or endoglacial (inside the glacier).

The Geoportal contains and presents the “recently” formed glacial lakes that originated in Aosta Valley region between 1975 and 2005 . The information was obtained mainly from the comparison of aerial orthophotos relating to different periods and from subsequent direct investigations on site. The lakes thus identified are over 120.

The presence and formation of glacial lakes represents so anevolution of the landscape but, in some cases, it can constitute a significant risk factor. In example the new formation of lakes that are generate as a result of the damming action of a moraine or a glacial dam during the retreat of a melting glacier. Other similar phenomena are linked to the formation of water pockets inside the glacier, which can potentially generate sudden emptying phenomena associated with the consequent formation of high flood waves and/or debris flows that could reach infrastructures or villages even at the valley bottom.

Some of the better known examples of these phenomena, which occurred in different sectors of the Alps, are the ephemeral Lake of Belvedere (2002), the ephemeral Lake of Rocciamelone (2004) and the Lake of Grindewald (2005). In these cases, in order to reduce the potential risk of sudden emptying phenomena, various interventions were carried out to drain the newly formed water accumulations.

Even in Aosta Valley region there were historical phenomena of floods or torrential lava resulting from the sudden emptying of glacial lakes: the most emblematic case is that of Lake Santa Margherita formed at the Rutor Glacier (La Thuile).

As evidence of this growing potential risk, there is the recent example of the neoformation of Lake Grand Croux (2018, Cogne) which formed at the front of the glacier, where Fondazione Montagna sicura - Montagne Sûre coordinated the risk mitigation activities.

CONSULTATION OF THE CARTOGRAPHIC GEOPORTAL

The Inventory is divided into a cartographic section and an associated database. On the cartography, the newly formed lakes are highlighted by a blue circle. Clicking on the maptip takes you to a form showing the data of major interest and an image. The data reported are the following:

  • the name of the lake, which is associated with the glacier of origin. If there are more lakes these are identified with a progressive numbering (eg Rutor I, Rutor II, etc.);

  • the Municipality of belonging;

  • the hydrological basin to which it belongs;

  • the surface (m²);

  • the perimeter (m);

  • the altitude (m a.s.l.);

  • the geographic coordinates of the centroid of the polygon representing the lake (expressed in UTM-ED50);

  • The identification code: it incorporates the code of the glacier to which it belongs according to the classification of the World Glacier Inventory (WGI) followed by the suffix "L" and the progressive number of the lake in the case of several lakes belonging to the same glacial apparatus (eg the lake Rutor IV will have the code I4L01516012 - L4);

  • origin: classification of the lake on the basis of itgenesis (dam, glacial contact, glacial excavation, etc.);

  • the characteristics of the banks: brief description of the materials that make up the bank dam (ice, rock, debris material, etc.);

  • the tributary: the presence or absence of a tributary stream;

  • the emissary: the presence or absence of an emissary stream;

  • the feeding (snow, snow-ice melting, etc.);

  • the localization method (orthophotography, GPS survey, etc.);

  • the year of the survey;

  • the date of the photograph.