Hazard Analysis of Hydrometeorological Concatenated Processes in the Colombian Andes

Abstract

The Colombian Andean region is characterized for its tropical climate and mountainous topography, where common short-duration and high-intensity rainfall events trigger progressive hydrometeorological phenomena that cause rapid concentration of streamflow as flash floods which, as their erosion capacity increases, may remobilize sediments and trigger slides creating debris floods torrents. When rainfall events exceed critical slope stability thresholds, clusters of landslides are triggered, especially on coarse residual soils increasing the sediment concentration and altering the fluid properties into a viscous mass surge of water and sediments. The final deposition of these materials is often located in basin fans that are usually highly populated resulting in huge disasters with high economic losses and fatalities. The most recent reports in Colombia include the events of Salgar in May of 2015 with 104 fatalities, Mocoa in March of 2017 with 400 people died. In this study, a regional hazard assessment methodology is proposed for flash floods, debris floods and channelized debris flows, considering the spatiotemporal variables, basin morphometry, sediment availability and rainfall data using statistical and physical methodologies to assess the susceptibility and hazard at a basin scale, resulting in a key tool for decision-making authorities.

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