From examination of natural events to a proposal for risk mitigation of lahars by a cellular-automata methodology: a case study for Vascún valley, Ecuador

Abstract

Abstract. Lahars are erosive floods, mixtures of water and pyroclastic detritus, known for being the biggest environmental disaster and causing a large number of fatalities in volcanic areas. Safety measures have been recently adopted in the threatened territories by constructing retaining dams and embankments in key positions. More disastrous events could be generated by the difficulty of maintaining these works in efficiency and for the changed risk conditions originating from their presence and the effects of their functioning. LLUNPIY/3r, a version of the cellular-automaton model LLUNPIY for lahar simulations, is presented. The growing frequency of lahars in the Vascún valley of Tungurahua volcano (Ecuador), probably due to the effects of the climatic change, has recently produced smaller and less dangerous events, sometimes favored by the collapse of ponds generated by small landslides. An investigation is performed here in order to reproduce such situations in a controlled way by the use of LLUNPIY/3r simulations. Using precise field data, points are individuated where dams by backfill, which are easy to collapse, can produce the formation of ponds; LLUNPIY/3r simulations permit projecting the triggering of small lahars by minor rainfall events or projecting, in the case of more rainfall, the anticipation of lahar detachment, avoiding simultaneous and dangerous confluence with other lahars.

LLUNPIY Simulations of the 1877 Northward Catastrophic Lahars of Cotopaxi Volcano (Ecuador) for a Contribution to Forecasting the Hazards

“…The present LLUNPIY model (lahar modeling by local rules based on an underlying pick of yoked processes, from the Quechua word "llunp'iy", meaning flood) is based on the CA computational paradigm for simulating primary and secondary lahars according to a general methodology developed for surface flows [19]. LLUNPIY was applied and validated in its various versions to past volcanic events, such as the 2005 and 2008 secondary lahars of Vascún Valley, Tungurahua Volcano, Ecuador [20][21][22][23][24][25], as well as the 1877 lahars flowing along the Río Cutuchi, Cotopaxi Volcano [20], and it was also applied to forecast future probable events [26,27].…”

“…The presence of a permanent glacier on the upper cone is one of the principal causes, together with volcanic eruptions (lava or pyroclastic flows and surges), of primary lahars, triggered by ice and snow melting [5,16,27,31]. The present Cotopaxi eruptive episode started in August 2015 and is still ongoing.…”

“…Outflow computation is performed in two steps: determination of the outflows f i toward the neighbor i, 1 ≤ i ≤ 6 according to the algorithm for the minimization of differences (AMD) [14,19], and determination of the shift of the outflows [21,[23][24][25][26][27].…”

Lagrangian modelling of a person lost at sea during the Adriatic scirocco storm of 29 October 2018

“…Data availability. Underlying observational and modeling data can be accessed at https://doi.org/10.5281/zenodo.3991755 (Licer et al, 2020).…”

Community Perception and Communication of Volcanic Risk from the Cotopaxi Volcano in Latacunga, Ecuador

“…Volcanic eruptions pose an enormous risk to Ecuador, because most of the exposed human settlements in the central and northern highlands are situated less than 25 km from an active volcano. Cities previously affected by volcanic eruptions include Quito, Latacunga, Salcedo, Cayambe, Ibarra-Otavalo, Ambato, Riobamba, and Baños [55]. Lahars have been among the deadliest volcanic hazards, but the emission of volcanic ash has been more frequent in the Ecuadorian Andes [56].…”