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

摘要

Lahars are erosive floods, mixtures of water andpyroclastic detritus, known for being the biggest environmental disaster andcausing a large number of fatalities in volcanic areas. Safety measureshave been recently adopted in the threatened territories by constructingretaining dams and embankments in key positions. More disastrous events couldbe generated by the difficulty of maintaining these works in efficiency andfor the changed risk conditions originating from their presence and theeffects of their functioning. LLUNPIY/3r, a version of the cellular-automaton model LLUNPIY for lahar simulations, is presented. The growingfrequency of lahars in the Vascún valley of Tungurahua volcano(Ecuador), probably due to the effects of the climatic change, has recentlyproduced smaller and less dangerous events, sometimes favored by thecollapse of ponds generated by small landslides. An investigation isperformed here in order to reproduce such situations in a controlled way by the useof LLUNPIY/3r simulations. Using precise field data, points are individuatedwhere dams by backfill, which are easy to collapse, can produce the formation ofponds; LLUNPIY/3r simulations permit projecting the triggering of small laharsby minor rainfall events or projecting, in the case of more rainfall, theanticipation of lahar detachment, avoiding simultaneous and dangerousconfluence with other lahars.