Fig. 2. Breach hydrographs used as inputs to simulate the Engaño Lake 1977 outburst flood.Figure optionsDownload full-size imageDownload as PowerPoint slide
1.5.2. Sensitivity analysis
Several flood simulations were undertaken to obtain an optimal set of parameters to model the Engaño River GLOF. Trials were performed using the SRTM and ASTER GDEM2 DEMs and different hydrographs and Manning values. Manning values ranging from 0.04 to 0.1 were tested since these AMN 082 values represent the range of roughness values of the Engaño channel and floodplain observed in the field. A one second time step was used in each simulation and the downstream boundary condition (i.e. energy slope) was held constant. The simulation results were contrasted from eye-witness accounts and the interpretation of satellite images.
2.1. GLOF preconditioning and potential triggering factors
Fig. 3. Glacier retreat and concomitant expansion of the Engaño Lake between 1955 and 2013. Icebergs are visible in the 1955 image indicating lake calving. The north lake shore was in contact with an avalanche cone prior to the 1977 GLOF.Figure optionsDownload full-size imageDownload as PowerPoint slide