GIS modeling of glacier lake outbursts
 
 

The integration of remote sensing data into GIS models is one of the major steps in AGREG. Therefore first modeling tests have been performed on locations where former lake outburst floods or debris flows are known. The Sirwolte lake outburst (1993) was chosen for first tests and model development. The Sirwolte lake is located south of the summit of the Simplon Pass (at the upper edge of the image).
The lake area was extracted from remote sensing data as outlined in the lake detection section, and then served as input to the GIS modeling.
The GIS modeling was performed in Arc/Info Grid where remote sensing raster data can be integrated. The raster cells of the lake were taken as starting cells for the simulation of the outburst flood. The runout and the spread out of the outburst flood is related to the probability that one specific cell is affected by the flood. As a controlling factor, a critical slope can be introduced which is defined on the basis of empirical data and defines the maximum runout point of the flood or related debris flow.
 
 
 
 

Simulation of the 1993 Sirwolte lake outburst flood, overlain on a shaded DEM (DHM25, L+T), the color range is related to the probability that a specific cell will be affected by the outburst flood (i.e. probability is decreasing from red to yellow, green and blue. The Sirwolte lake is shown in blue.).
 
 

Modeling the June 25, 2001 lake outburst and debris flow of Täsch, Valais

Two models for the Täsch lake outburst and subsequent debris flow: A modified single-flow direction approach implemented in a GIS (left) and a multiple-flow direction approach programmed outside a GIS (right). Both models use information on the Lake Weingarten extracted from satellite data. The color range is related to the probability that a specific cell will be affected by the debris flow. The flow model stops when a critical threshold of the average slope is reached.