Methodology for mudflow hazard assessment triggered by rainfall, in El Rollo Watershed, San Bernardo, Nariño

Abstract

Torrential rainfalls are considered destructive processes that take place around the world, these are generated in mountainous areas and are deposited in alluvial fans or plains commonly occupied by human settlements, hence transporting a large volume of sediment, this case particularly applies for “El Rollo” creek micro-basin, its water network flows throughout the
urban area of “San Bernardo” village, therefore, it shows a potential for the occurrence of this kind of event. In this work, a methodology was conducted by the implementation of Geographic Information Systems was carried out for the evaluation of the threat due to the flow of sludge formed under rain events. The implementation of a mathematical FLO-2D model allowed a rainfall to flow transition used to determinate the hydric characteristics on the area, subsequently, the threat level in the basin is evaluated through the modeling of a torrential event proposed for different scenarios, establishing depths and peak flow speed rates for each setting over potential deposition zones. Once the simulation results were obtained a hazard map was developed based on the event intensity and its frequency of occurrence.