New method for assessing the susceptibility of glacial lakes to outburst floods in the Cordillera Blanca, Peru

摘要

This paper presents a new and easily repeatable method for assessing thesusceptibility of glacial lakes to outburst floods (GLOFs) within thePeruvian region of the Cordillera Blanca. The presented method was designedto: (a) be repeatable (from the point of view of the demands on input data),(b) be reproducible (to provide an instructive guide for differentassessors), (c) provide multiple results for different GLOF scenarios and(d) be regionally focused on the lakes of the Cordillera Blanca. Based onthe input data gained from remotely sensed images and digital terrain models/topographicalmaps, the susceptibility of glacial lakes to outburst floodsis assessed using a combination of decision trees for clarity and numericalcalculation for repeatability and reproducibility. A total of seventeenassessed characteristics are used, of which seven have not been used in thiscontext before. Also, several ratios and calculations are defined for thefirst time. We assume that it is not relevant to represent the overallsusceptibility of a particular lake to outburst floods by one result(number), thus it is described in the presented method by five separateresults (representing five different GLOF scenarios). These are potentialsfor (a) dam overtopping resulting from a fast slope movement into the lake,(b) dam overtopping following the flood wave originating in a lake situatedupstream, (c) dam failure resulting from a fast slope movement into thelake, (d) dam failure following the flood wave originating in a lakesituated upstream and (e) dam failure following a strong earthquake. All ofthese potentials include two or three components and theoretically rangefrom 0 to 1. The presented method was verified on the basis of assessing thepre-flood conditions of seven lakes which have produced ten glacial lakeoutburst floods in the past and ten lakes which have not. A comparison ofthese results showed that the presented method successfully identified lakessusceptible to outburst floods (pre-flood conditions of lakes which havealready produced GLOFs).