River bed sediments typically fine downstream, where fining of median grain sizes are often described as exponential, except gravel abruptly transitions to sand. Across the gravel-sand transition, can reduce by more than 10 mm (>90%) over a distance only few channel widths. There several viable theories for why transition occurs, but they remain matter ongoing discussion in literature. Here, we...

The potential for in situ biodegradation of 4-nonylphenol (4-NP) was investigated in three hydrologically distinct streams impacted by wastewater treatment plants (WWTPs) in the United States. Microcosms were prepared with sediments from each site and amended with [U-ring-(14)C]4-n-nonylphenol (4-n-NP) as a model test substrate. Microcosms prepared with sediment collected upstream of the WWTP o...

We investigate the use of the short-lived fallout radionuclide beryllium-7 ( Be; t1/2 = 53·4 days) as a tracer of medium and coarse sand (0·25–2 mm), which transitions between transport in suspension and as bed load, and evaluate the effects of impoundment on seasonal and spatial variations in bed sedimentation. We measure Be activities in approximately monthly samples from point bar and stream...

A numerical model that couples water flow and sediment transport over a non-cohesive bed is developed to simulate the initiation and evolution of transportational cyclic steps. Transportational cyclic steps are periodic bedforms characterized by corresponding hydraulic jumps that form when a supercritical flow erodes and deposits bottom sediments on a steep bed. The flow transition at the hydra...

Roles of the vegetation to mitigate the erosion of the stream bed or to facilitate the deposition of the fine sediments by the species of the aquatic plants were presented. Field investigation on the estimation of the change of the bed level and the estimation of the flow characteristics were performed. The results showed that Phragmites japonica has the mitigation function of 0.3m-0.4m of the ...