Flooding Hazard Due to Waterlogging In The Aranda Expansion Area - Pasto, Nariño

Abstract

This study investigates the flooding hazard caused by waterlogging in the Aranda expansion zone of Pasto municipality, utilizing a critical design rainfall with a return period of 100 years. The hydrological conditions of the study area were delineated by defining the basin belonging to the Aranda expansion zone, corresponding to the El Blanco micro-watershed. Maximum precipitation data from three meteorological stations were employed to determine precipitation intensities for various durations based on the IDF curves. The MIKE SHE software simulated surface flow depths and velocities across the study area, considering land cover, soil hydrological characteristics, infiltration, slope, and calculated rainfall intensities. Flood hazard zoning, employing FEMA and IDIGER methodologies, revealed that steep slope areas exhibited a medium flood hazard due to the potential for flash flooding. Although the initial focus was on waterlogging in the expansion zone of the basin plain, the results indicated that the topographic conditions, characterized by steep slopes with high run-off velocities, warranted assigning a medium hazard level to these regions due to their heightened susceptibility to flash flooding. However, most of the micro-watershed demonstrated a low threat of flooding due to waterlogging, attributed to deep, well-drained soils facilitating infiltration and temporary water storage, thereby reducing surface water accumulation. These findings underscore the significance of considering hydrological characteristics in planning for this area, particularly within El Blanco micro-watershed.