Article
Geology
Alexander R. Beer, Michael P. Lamb
Summary: River incision into bedrock plays a key role in landscape evolution and links surface changes to climate and tectonics. Experimental results suggest that under high impact energy conditions, rivers may generate larger rock fragments.
Article
Mechanics
Yesheng Lu, Nian-Sheng Cheng, Maoxing Wei
Summary: Difficulties in estimating bed shear stress in vegetated flows are addressed in this study using an analytical approach based on the phenomenological theory of turbulence, without empirical partition of bed friction and vegetation resistance. The computed bed-load transport rate in vegetated flows aligns well with the formula for unvegetated flows, and the method is applicable to both uniformly distributed vegetation and vegetation patches. However, further research is necessary to extend the model to flexible and submerged vegetation conditions.
Article
Environmental Sciences
Robert I. Ferguson
Summary: Logarithmic and variable-power equations using D-84 grain size as roughness metric can reproduce the flow resistance trend in streams with coarse beds, but are unreliable for predictions in individual reaches. A proposed method of calibrating an effective roughness height through a single flow measurement significantly reduces root-mean-square error in predicting velocity compared to using D-84.
WATER RESOURCES RESEARCH
(2021)
Article
Geography, Physical
Larry Syu-Heng Lai, Joshua J. Roering, Noah J. Finnegan, Rebecca J. Dorsey, Jiun-Yee Yen
Summary: The incision rate and steepness of bedrock channels are primarily controlled by coarse-sediment supply, while the bedrock properties on hillslopes in the source area influence channel steepness. Channel steepness is independent of rock uplift rate and annual precipitation, but systematically varies with sediment size, substrate strength, and sediment source rock in fluvial bedrock channels along the Coastal Range in eastern Taiwan. Models assuming a proportionality between incision rate and basal shear stress may not fully capture controls on fluvial channel profiles in landslide-dominated landscapes, where other processes such as bedload impacts and debris-flow scour may play significant roles in balancing rock uplift and incision.
EARTH SURFACE PROCESSES AND LANDFORMS
(2021)
Article
Environmental Sciences
Marwan A. Hassan, Matteo Saletti, Conor McDowell, Wenqi Li
Summary: Based on an extensive 18-year data set from East Creek in British Columbia, field observations indicate that the step-pool morphology remains stable under a wide range of flows. Most events show no significant changes in sediment storage, and the mobility of sediment particles is controlled by sediment supply rather than flow magnitude.
WATER RESOURCES RESEARCH
(2023)
Article
Engineering, Civil
Sobhan Moradi, Kazem Esmaili, Saeed Reza Khodashenas
Summary: This study experimentally analyzes the impact of a floodplain's parallel wall with a compound meandering main channel on hydraulic flow. Various hydraulic parameters were considered, and measurements were taken at different cross sections. The results showed that lower relative depths contribute to higher flood damage due to vortexes and turbulence intensity. The study also identified optimal positions for hydraulic investigation in meandering rivers and observed sediment deposition patterns. The ratio of flow velocities in the inner and outer banks differed, and increasing relative depth affected velocity ratios and bed shear stress.
JOURNAL OF HYDROLOGY
(2023)
Article
Environmental Sciences
Ming Tang, Heqin Cheng, Yijun Xu, Hao Hu, Shuwei Zheng, Bo Wang, Zhongyong Yang, Lizhi Teng, Wei Xu, Erfeng Zhang, Jiufa Li
Summary: This study assessed the evolution and response mechanism of the South Channel and South Passage in the Yangtze Estuary using hydrology, multibeam echo sounding, and historical bathymetry data. The results showed that the channel experienced substantial deposition and bed erosion during different time periods, and it is likely to continue aggrading due to human activities.
Article
Environmental Sciences
L. E. Polvi
Summary: In northern Fennoscandia, the landscape context of semi-alluvial rapids leads to low amounts of fine sediment and incompetent flows to transport boulders.
WATER RESOURCES RESEARCH
(2021)
Article
Geosciences, Multidisciplinary
Clarke Delisle, Brian J. Yanites
Summary: This study focuses on the sensitivity of hillslope sediment supply to precipitation events and its implications on river evolution. By modeling long-term evolutionary processes, it is found that the sensitivity of sediment supply strongly influences the driving water discharge events for river incision and modulates channel morphology.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2023)
Article
Geosciences, Multidisciplinary
Tingan Li, Jeremy G. Venditti, Colin D. Rennie, Peter A. Nelson
Summary: Approximating the stresses on the bed and walls of confined, narrow bedrock rivers is crucial for accurately understanding hydraulic roughness, sediment transport, bedrock erosion, and the dynamics of bedrock channels. Through the use of the ray-isovel model (RIM) and field observations, this study found that the distribution of shear stress across an idealized trapezoidal channel is influenced by the angle of the river banks and the width-to-depth ratio. The study also revealed that the complex flow structure in bedrock canyons affects the distribution of bed and wall stresses, with the bedrock walls contributing more hydraulic roughness than predicted by the RIM model.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2022)
Article
Geography, Physical
Chenge An, Marwan A. Hassan, Carles Ferrer-Boix, Xudong Fu
Summary: Results from experiments show that conditioning flow can reduce sediment transport rate during subsequent floods, but this effect is limited to a relatively short time at the beginning of the flood event. The stress history effect induced by bed reorganization during conditioning phase is likely to be erased with increasing flow and sediment transport intensity during the subsequent flood event.
EARTH SURFACE DYNAMICS
(2021)
Article
Engineering, Civil
Xiang Wang, Carlo Gualtieri, Wenxin Huai
Summary: The impact of aquatic vegetation on weak bed-load transport rates in riverbeds was investigated through laboratory experiments. It was observed that the transport rate increased with an increase in energy slope and a decrease in vegetation density. The traditional method of calculating bed shear stress was unable to predict the measured transport rate, but a new method considering grain shear stress provided a reasonable prediction. The proposed models were found to be more accurate than existing literature models, improving understanding of bed-load transport in vegetated flows.
JOURNAL OF HYDROLOGY
(2023)
Article
Environmental Sciences
Nargess Moghaddassi, Seyed Habib Musavi-Jahromi, Mohammad Vaghefi, Amir Khosrojerdi
Summary: The study shows that changing the mean velocity-to-critical velocity ratio significantly affects the maximum scour depth and sedimentary height at the downstream bend of a meandering channel. Additionally, incipient motion occurs at the upstream and downstream bends under different ratio conditions.
Article
Geosciences, Multidisciplinary
Guilherme Kruger Bartels, Nilza Maria dos Reis Castro, Gilberto Loguercio Collares, Fernando Mainardi Fan
Summary: This study evaluated the performance of five bedload equations in a mixed bedrock-alluvial stream, finding that using reduced shear stress and reduction factor of available bed material together improves prediction accuracy. The equations tended to overestimate bedload transport rate, indicating an underestimation of energy loss in mixed bedrock-alluvial channels.
Article
Environmental Sciences
Michele Trevisson, Olivier Eiff
Summary: The study investigates the long-term evolution of fine sediment ribbons in rivers and the influence of immobile grains on the erosion process. Through flume experiments, the researchers found that ridges formed by immobile grains are the main sediment source, while troughs are quickly eroded to a stable bed level. The erosion rates over ridges and troughs follow a sequence of four regimes, which are controlled by the height of ridges and the lateral roughness heterogeneity.
WATER RESOURCES RESEARCH
(2022)