Análisis de la peligrosidad de las inundaciones causadas por los ríos Lía, Pichilo y Conumo, en la provincia de Arauco.
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Date
2026
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Universidad de Concepción
Abstract
La presente memoria de título tiene como objetivo principal analizar la peligrosidad de las inundaciones causadas por las crecidas de los ríos Lía, Pichilo y Conumo en la provincia de Arauco. El área de estudio se caracteriza por una topografía plana y una vulnerabilidad creciente debido al aumento poblacional en las planicies de inundación, con una probabilidad de inundaciones dañinas estimada cada 1.77 años. Para este análisis, se desarrolló un modelo hidrodinámico bidimensional en el software Iber, cubriendo una superficie de 1,540 hectáreas. Debido a la incertidumbre en los datos fluviométricos de caudales máximos, el modelo fue calibrado utilizando la crecida ocurrida entre el 14 y 16 de junio de 2025, empleando coeficientes de rugosidad de Manning (0.035 para cauces y 0.05 para planicies) determinados mediante la caracterización granulométrica del lecho D50). La validación se realizó con el evento de junio de 2024, alcanzando un Critical Success Index (CSI) de 0.744, lo que demuestra su alta capacidad predictiva. A través de la simulación de nueve periodos de retorno, se determinaron áreas de inundación que varían entre 891.3 hectáreas (T=2) y 1,040.1 hectáreas (T=200). Los resultados identificaron al puente Conumo Chico como un control hidráulico crítico, cuyo efecto de peralte provoca un trasvasije de caudales hacia la cuenca del estero El Molino que representa entre el 36% (T=2) y el 58% (T=200) del flujo peak del río Conumo. El análisis de peligrosidad, bajo los criterios de la DOH, revela que el 61.96% de la mancha de inundación para un evento frecuente de 2 años ya presenta una peligrosidad alta. Esta condición afecta de forma recurrente a los sectores de Carampangue, Conumo Bajo, Pichilo y La Faja, entregando una base técnica fundamental para la definición y evaluación de medidas de mitigación en las etapas posteriores del proyecto.
The main objective of this project is to analyze the flood hazard caused by the Lía, Pichilo, and Conumo rivers in the Arauco Province. The study area is characterized by flat topography and increasing vulnerability due to population growth in floodplains. Given the high recurrence of these events, with a damage-inducing flood probability estimated every 1.77 years, the study focuses on diagnosing hydraulic behavior during periodic floods of varying magnitudes. For this analysis, a twodimensional hydrodynamic model was developed using Iber software, covering an area of 1,540 hectares. Due to uncertainty in fluviometric data for major events, the model was calibrated using the flood occurring between June 14 and 16, 2025, employing Manning's roughness coefficients (0.035 for riverbeds and 0.05 for floodplains) determined through bed granulometry D50 characterization). Validation was performed using the June 2024 flood event, achieving a Critical Success Index (CSI) of 0.744, which demonstrates high predictive capacity. Through the simulation of nine return periods, flood areas were determined to range from 891.3 hectares for T=2 to 1,040.1 hectares for T=200. The results identified the Conumo Chico bridge as a critical hydraulic control, with its backwater effect causing a flow diversion toward the El Molino stream basin, representing between 36% (T=2) and 58% (T=200) of the Conumo River's peak flow. The hazard analysis, following DOH criteria, reveals that 61.96% of the flooded area for a frequent 2-year event already presents a high hazard level. This condition repeatedly affects the inhabited sectors of Carampangue, Conumo Bajo, Pichilo, and La Faja, providing a fundamental technical basis for defining and evaluating mitigation measures in subsequent project stages.
The main objective of this project is to analyze the flood hazard caused by the Lía, Pichilo, and Conumo rivers in the Arauco Province. The study area is characterized by flat topography and increasing vulnerability due to population growth in floodplains. Given the high recurrence of these events, with a damage-inducing flood probability estimated every 1.77 years, the study focuses on diagnosing hydraulic behavior during periodic floods of varying magnitudes. For this analysis, a twodimensional hydrodynamic model was developed using Iber software, covering an area of 1,540 hectares. Due to uncertainty in fluviometric data for major events, the model was calibrated using the flood occurring between June 14 and 16, 2025, employing Manning's roughness coefficients (0.035 for riverbeds and 0.05 for floodplains) determined through bed granulometry D50 characterization). Validation was performed using the June 2024 flood event, achieving a Critical Success Index (CSI) of 0.744, which demonstrates high predictive capacity. Through the simulation of nine return periods, flood areas were determined to range from 891.3 hectares for T=2 to 1,040.1 hectares for T=200. The results identified the Conumo Chico bridge as a critical hydraulic control, with its backwater effect causing a flow diversion toward the El Molino stream basin, representing between 36% (T=2) and 58% (T=200) of the Conumo River's peak flow. The hazard analysis, following DOH criteria, reveals that 61.96% of the flooded area for a frequent 2-year event already presents a high hazard level. This condition repeatedly affects the inhabited sectors of Carampangue, Conumo Bajo, Pichilo, and La Faja, providing a fundamental technical basis for defining and evaluating mitigation measures in subsequent project stages.
Description
Tesis presentada para optar al título de Ingeniero/a Civil.
Keywords
Inundaciones, Inundaciones Chile Octava región, Ríos