Numerical modelling of a flash-flood event at Peribán de Ramos, Michoacán (Mexico)

ABSTRACT During the afternoon of 23 September 2018, a flash flood event occurred at Peribán de Ramos (Michoacán, Mexico). This event was triggered by 2-h precipitation of 58 mm, affecting at least 100 families, damaging 30 houses and killing 8 people. We present the first assessment of this event, for which we carried out stratigraphic descriptions, took sedimentological samples of the deposits and performed numerical simulations with the FLO-2D model to recreate the flow. Our results present a good fit with the flow heights, velocities, and the distribution of the flood zones observed in the field. We additionally performed a flood hazard assessment based on a rainfall frequency analysis for extreme events of 2-h duration at different return periods. Results show that even the 2-year event would reach flow depths >5 m and velocities exceeding 6.5 m/s, causing the overspill of Cutio river, affecting ~1500 inhabitants and avocado farming lands, causing a bigger impact on the population’s incomes and their way of life. We consider that these types of events could become more frequent and of major magnitude due to the change in land cover and land use, obstruction of natural drainages and changes in precipitation patterns in response to climate change.