PUBLICACIÓN

ARTÍCULO

Rainfall-triggered lahars at Volcán de Colima, Mexico: Surface hydro-repellency as initiation process

L.Capra, L. Borselli, N. Varley, J.C. Gavilanes, D. Sarocchi, L. Caballero, G. Norini
Journal of Volcanology and Geothermal Research 189 (1-2): 105-117. , 2010.

ABSTRACT:

VolcándeColimaiscurrentlythemostactivevolcanoinMexico.Since1998intermittentactivityhasbeen observedwithvulcanianeruptions,lava &#64258;owsandgrowingdomesthathavecollapsedproducingseveral block-and-ash &#64258;owdeposits.Duringtheperiodofheightenedactivitysince1998atVolcándeColima, pyroclastic &#64258;owsfromdomeorcolumncollapsehavenotreachedlongdistances,mostofthetimelessthan 6kmfromthecrater.Incontrast,rain-inducedlahars weremorefrequentandhavereachedrelativelylong distances,upto15km,causingdamagetoinfrastructureandaffectingsmallvillages.In2007tworaingauge stationswereinstalledonthesouthern &#64258;ankofthevolcanoregisteringeventsfromJunethroughtoOctober, theperiodwhenrainsareintenseandlaharsfrequent.Bycomparinglaharfrequencywithrainfallintensity andtherainfallaccumulatedduringtheprevious3days,laharsmorefrequentlyoccuratthebeginningof therainfallseason,withlowrainaccumulation(<10 mm)andtriggeredbylowrainintensities(<20mm/ h).Duringthemonthswithmorerainfall(JulyandAugust)laharsarelessfrequentandhigherpeak intensities(upto70mm/h)areneededtotriggeranevent.Inbothcases,laharswereinitiatedasdilute, sediment-ladenstream&#64258;ows,whichtransformedwithentrainmentofadditionalsedimentintohypercon- centratedanddebris &#64258;ows,withalternationsbetweenthesetwo &#64258;owtypes.Ahydro-repellencymechanism inhighlyvegetatedareas(i.e.evergreentreetypeswithconsiderableamountofresinsandwaxessuchas pines)withsandysoilscanprobablyexplainthehighfrequencyoflaharsatthebeginningoftherainseason duringlowrainfallevents.Underhydrophobicconditions,in&#64257;ltrationisinhibitedandrunoffisfacilitatedat morehighlypeakeddischargesthataremorelikelytoinitiatelahars. ©2009ElsevierB.V.Allrightsreserved.