Browsing by Author "Petrie, John E."

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Influence of characteristic diameter on downstream hydraulic geometry relations for a high gradient gravel bed river
(American Society of Civil Engineers (ASCE), 2022) Pacheco Tobar, Esteban Alonso; Petrie, John E.; Carrillo Serrano, Verónica Margarita
Hydraulic geometry (HG) theory has been applied to characterize the morphological changes that a river undergoes as a result of changes in discharge. Furthermore, HG has been used in a variety of studies including indirect discharge estimates, habitat assessment, and flow resistance analysis. Since a river is always evolving towards a morphological equilibrium, HG relations are obtained based on measured data that relate top width, mean flow depth, and mean velocity with discharge. At-a-station and downstream HG have been defined to characterize river development at a cross-section and reach scales, respectively. Dimensionless forms of downstream HG relations have been proposed to capture the physics of river morphology. Median sediment diameter d50has been used as the characteristic diameter to put HG relations in dimensionless form. However, for rivers with coarse bed material, it has been shown that the characteristic diameter may be greater than d50. In the present study, field measurements from a high gradient (slopes from 2% to 10%) gravel bed river (d50from 4 to 25 mm), the Tabacay River, are used to establish the downstream HG relations and to determine the impact of the characteristic diameter by considering d84and d90as characteristic diameters. Additionally, based on these relations, regime equations are obtained for the Tabacay River to compare the performance of each characteristic diameter. The results helped to define the appropriate characteristic diameter to make HG relations and regime equations more representative of measured data.
Validation of an experimental procedure to determine bedload transport rates in steep channels with coarse sediment
(2021) Padilla Guarnizo, Carlos Ramiro; Cisneros Espinoza, Felipe Eduardo ; Carrillo Serrano, Verónica Margarita; Petrie, John E.; Timbe Castro, Luis Manuel; Pacheco Tobar, Esteban Alonso; Astudillo Matute, Washington Santiago
The current study presents an experimental procedure used to determine bedload sediment transport rates in channels with high gradients and coarse sediment. With the aim to validate the procedure for further investigations, laboratory experiments were performed to calculate bedload transport rates. The experiments were performed in a laboratory tilting flume with slopes ranging from 3% to 5%. The sediment particles were uniform in shape (spheres). The experiments were divided into four cases based on sediment size. Three cases of uniform sizes of 10 mm, 15 mm and 25 mm and a case with a grain size distribution formed with the uniform particle sizes were considered. From the experimental results a mathematical bedload transport model was obtained through multiple linear regression. The experimental model was compared with equations presented in the literature obtained for gravel bed rivers. The experimental results agree with some of the models presented in the literature. The closest agreement was seen with models developed for steep slopes especially for the highest slopes considered in the present study. Therefore, it can be concluded that the methodology used can be replicated for the study of bedload transport rates of channels with high gradients and coarse sediment particles to study more general cases of this process such as sediments with non-uniform shapes and sizes. However, a simplified model is proposed to estimate bedload transport rates for slopes up to 5%.