Obtención de parámetros cuantitativos de lahares en la quebrada Palmacuru del Volcán Tungurahua mediante la calibración de los detectores de tipo acoustic flow monitor AFM

Abstract

Quantitative flow parameters have been obtained for the secondary lahars occurred between March 2012 and March 2015 in the Palmaurcu drainage at Tungurahua volcano. Three instruments of Acoustic Flow Monitor type (AFM) are located along this drainage for detecting lahars. Previously, they only allowed to perform qualitative assessments, but after a calibration of the instruments was possible to quantify lahars. A database of all events that occurred during the study period was generated, according to the information contained in the weekly bulletins issued by the staff of the Tungurahua Volcano Observatory and a comparison with the records of the lahar detection system. In order to calculate the lahar discharge, after its occurrence, field measurements were needed. The method used for estimating the speed was the vortex forced equation that considers the super elevation principle. The necessary variables were purchased by using a laser telemeter, also to determine the flooded cross sections. Peak flow discharge is related to the maximum amplitude recorded by the instruments for several lahars. The result is a linear correlation equation which allows the processing of AFM records in instant flow discharge. Through an analysis of significance it was determined that the regressions for two stations allow valid estimates, while the equation for the third station is not useful under present conditions. For each lahar it was possible to estimate the average flow discharge, the peak flow discharge and its volume. In addition, the total volume of all produced lahars was estimated. Moreover, by analyzing the AFM records, a method to classify lahars according to their behavior (hyperconcentrated flows and debris flows) is proposed.