Abstract
Abstract. The growing number of glacial margin lakes that have developed due to glacier retreat, have caused an increase of dangerous Glacial Lake Outburst Floods (GLOFs) in several regions over the last decade. A GLOF can occur when the water from the lake finds a path underneath the bottom of the glacier and the lake is draining rapidly. This causes normally a flood wave downstream the glacier. Typically such an event takes about 24 hours. GLOF scenarios may be a significant hazard to life, property, nature and infrastructure in the affected areas. Together with our partner institute CECS (Valdivia, Chile), a project was initiated on a pilot study for an early warning system for GLOF events in the Northern Patagonian Icefield. A GLOF is normally characterized by a progressive water level drop. By observing the water level of the lake, an imminent GLOF-event can be identified. Common gauging systems are not suitable for the measurement task, as they may be affected by ice fall or landslides in the lake basin. Therefore, in our pilot study the water level is observed by processing images of a terrestrial camera system. The paper presents the basic principle of a single-camera based GLOF early warning system. Challenges and approaches to solve them are discussed. First results from processed image sequences are presented to show the feasibility of the concept. Water level changes can be determined at decimetre precision. In the first stage of the project, the waterline was measured manually in the images. A promising approach for reliable automation of this task is the use of a camera, which is sensitive for near infrared. The difference in the reflection of water, ice, and rock in this wavelength is more better than in RGB. This will be discussed in the outlook in deep.
Highlights
Glacial margin lakes are water bodies next to a glacier
The typical Glacial Lake Outburst Floods (GLOFs) mechanism is described by the ‘Glen mechanism’ (Glen, 1954): The increasing hydrostatic pressure of a glacier margin lake together with the decreasing detention from a thinning glacier enforces the development of a tunnel at the glacier bottom, through which the lake drains
One GLOF event is evident in the data between 12th and 15th December
Summary
Glacial margin lakes are water bodies next to a glacier (figure 1). The glacier functions as a dam, restraining the water of the lake (Raymond et al, 2003). Glacial margin lakes may drain within minutes to days These phenomena are called GLOF’s (Glacier Lake Outburst Flood). The typical GLOF mechanism is described by the ‘Glen mechanism’ (Glen, 1954): The increasing hydrostatic pressure of a glacier margin lake together with the decreasing detention from a thinning glacier enforces the development of a tunnel at the glacier bottom, through which the lake drains. During the process, this tunnel is widened by melting and erosion, causing a progressive lake drainage process. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W3, 2013 The Role of Geomatics in Hydrogeological Risk, 27 – 28 February 2013, Padua, Italy camera image water line
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