Analysis of vertical flow velocity and suspended sediment concentration profiles in Tumbes River during El Niño and La Niña events (#1859)

Authors

MENDOZA SULCARAY, RENZO DAMPIER

CAMPAÑA TORO, ROBERTO LUIS

ARMIJOS CÁRDENAS, ELISA NATALIA

MORERA JULCA, SERGIO BYRON

Abstract

The Tumbes region, located in northern Peru, is affected by the extreme climatic events El Niño and La Niña. Due to the intense precipitation caused by the El Niño phenomenon, high water flows and sediments are generated; conversely, La Niña causes precipitation deficits and therefore lower liquid flows, and sediment loads than El Niño. The objective of this study is to analyze the vertical flow velocity profiles and suspended sediment concentration measured at the El Tigre hydrometric station on the Tumbes River, located 50 km upstream from the Pacific Ocean estuary, during flood periods in the El Niño events of 2017 and the La Niña events of 2018. Vertical flow velocity profiles measured with a Doppler effect current meter were modeled using the theoretical velocity distribution of the log-wake type by adjusting the parameters of shear velocity, distance from the bed at which theoretically the flow profile velocity becomes zero, and the wake parameter. Vertical suspended sediment concentration profiles were modeled using the theoretical suspended sediment concentration distribution resulting from the parabolic-linear distribution of the fluid mixing coefficient by adjusting the parameters of mean diameter of suspended sediments and reference suspended sediment concentration near the bed. It was concluded that the vertical flow velocity profiles and suspended sediment concentration profiles recorded during the El Niño event of 2017 and La Niña event of 2018 reasonably fitted the theoretical velocity distribution of the log-wake type and the theoretical concentration distribution of suspended sediments resulting from the parabolic-linear distribution of the fluid mixing coefficient. Using the adjusted models, it was estimated that the mean sizes of suspended sediments calculated for the El Niño event of 2017 (62 to 132 µm) were approximately 2 times those calculated for La Niña of 2018 (25 to 67 µm), and that the reference concentrations of suspended sediment at the bed level calculated for the El Niño event of 2017 (254 to 1766 mg/l) were approximately 7 times those calculated for La Niña of 2018 (95 to 250 mg/l).