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.
Assessing Unit Hydrograph Parameters and Peak Runoff Responses from Storm Rainfall Events: A Case Study in Hancheon Basin of Jeju Island