Debris flows triggered from melt of seasonal snow and ice within the active layer in the semi-arid Andes

MOREIRAS, STELLA M.; FERRANDO ACUÑA, FRANCISCO J.; VERGARA DAL PONT, IVAN; ARANEO, DIEGO; SANTIBAÑEZ OSSA, FERNANDA A.

PERMAFROST AND PERIGLACIAL PROCESSES

JOHN WILEY & SONS LTD

Lugar: Londres; Año: 2019 vol. 31 p. 57 - 68

1045-6740

Debris flows triggered from rapid melt of seasonal snow, and/or ice within the active layer have not been studied in periglacial areas of the semi-arid Andes. Therefore, through a representative watershed we investigated the thermo-radiative characteristics, the possible water sources, and the current and future frequency of these debris flows. Information was collected on three temporal clusters of debris flows during which no rains and major earthquakes occurred. The thermo-radiative conditions of each cluster were analysed through nearby stations that cover the entire watershed altitudinal range. Snow covers were calculated using the closest satellite images before and after each cluster in order to evaluate the potential snowmelt contribution for each. The frequency of melting-driven debris flows, for the remainder of the 21st century was evaluated by calculating the trends of climatic variables that control them. The results indicate that debris flows present several patterns such as: lag of some hours between the warmest daily hours and their triggering, occurrence in clusters of 3-5 days during the early summer, and accelerated increase of temperature during the previous days to the clusters beginnings. In addition, it was inferred that the water of debris flows can come from the melt of seasonal snow as well as of shallow ice within the active layer. Lastly, due to the positive trend of the maximum air temperature of warmer trimester and the high inter-annual variability of precipitation, a frequency increase is likely, followed by a possible decrease due to the negative and positive trends of precipitation and mean air temperature, respectively.