Análisis del coeficiente de rugosidad en ríos de montaña mediante la aplicación de modelos hidráulicos bidimensionales (2D)

Abstract

One of the main input parameters in a 2D hydrodynamic modeling is the roughness coefficient. To establish its value, various resources are used, such as; empirical equations, tables and photographs. Nonetheless, quantifying the value of the fluvial morphology of a river mountain can generate an error up to 30% since flow resistance is a complex phenomenon. In the current paper, various methodologies were analyzed to predict the Manning's n coefficient. For this purpose, it was introduced an uncertainty obtained after varying the coefficient between +/- 10% and +/-30%. Three high variable mountain zones in terms of morphology of the Quinuas river were selected so that field data could be obtained. The corresponding evaluation was carried out by comparing different water levels measured in area vs the water levels average, generated after the Iber 2D hydrodynamic modeling. The dimensionless methodologies proved a better performance to predict roughness coefficient, using a u another does not represent a significant alteration for the same flow rate and morphology. However, the rest of the methodologies displayed a similar performance when compared to dimensionless ones. The Cascade morphology registers less sensitivity to roughness coefficient variations, followed by the Step-pool methodology, and the higher sensitivity was displayed by the Plane-bed morphology. It is worth mentioning that in general terms methodologies follow a tendency; there is a lower performance for the following conditions: low flow, morphologies with less bed slope, and for low values in the roughness coefficients.