Displacement characteristics of coarse fluvial bed sediment

Abstract

[1] Previous work highlights the need for data collection to identify appropriate models for temporal evolution of tracer dispersal in rivers. Results of 64 gravel-bed field tracer experiments covering a wide range of flow and sediment supply regimes are compiled here to determine the probabilistic character of gravel transport. We focus on whether particle travel distances and waits are thin-or heavy-tailed. While heavy-tailed travel distance distributions are observed between successive monitoring events in different hydrological and sediment supply regimes, heavy-tailedness does not persist through total travel distance over multiple monitoring events, suggesting that individual monitoring events occur before particle travel distance exceeds the characteristic correlation length for the channel (such that particles that start in fast paths remain in fast paths and particles in slow paths remain in slow paths). After a large number of transport events, super-diffusive spreading was not observed at any of the gravel bed streams. Continuous-time tracking of x, y, z coordinates of tracers in natural streams is necessary to capture exact step and waiting time distributions.

Quality assessment and classification of Ogbese river using water quality index (WQI) tool

“…DO variations ranged from 4.7 to 16.0 mg/L with mean value of 10.23 ± 3.70 mg/L for dry season and 3.3 to 7.0 mg/L with mean value of 4.44 ± 0.91 mg/L for wet season, respectively. DO values were within WHO and NSDWQ permissible limits but above FAO value of 2 mg/L, the slight reduction in DO during the wet season might be due to the higher influx of wastes thereby reducing the biological life of the river which agreed with the findings of Hassan et al (2013). The implications of this were that the water would not be suitable for public/domestic supply and recreational purposes, and that it would weaken the activities of aquatic organisms in the river and the DO reduction will also prevent the establishment or distortion of the usual flora and fauna of Ogbese River.…”

Dynamics and mechanics of bed-load tracer particles

“…Examining passive tracers in the field introduces an ambiguity; one measures particle displacement -i.e., the distance a particle travels between successive surveys of its position -but this displacement is composed of an unknown number of steps and rests. Displacement length distributions measured for individual floods, and at longer timescales over many floods, typically follow exponential or gamma-like distributions (Hassan et al, 1991;Schmidt and Ergenzinger, 1992;Habersack, 2001;Lamarre and Roy, 2008;Bradley and Tucker, 2012;Hassan et al, 2013;Phillips et al, 2013). We propose two simple limits for particle displacement during a flood: (1) the lower limit is that a particle executes a single step, with a characteristic length scale predicted by Eq.…”

Monitoring Riverbank Erosion in Mountain Catchments Using Terrestrial Laser Scanning

“…Soil erosion has several on-site and off-site impacts on the environment: (1) loss of fertile soil with important consequences on agriculture [1]; (2) silting of reservoirs that reduces the storage capacity and interferes with dam operations [2][3][4]; (3) migration of pollution in which sediment transport is considered a means of transport for contaminants [5,6]; (4) increase of flood risk [7] and debris flow events [8]; and (5) geomorphic evolution of river beds [9] with possible impacts on the surrounding structures. At the basin scale, sediment production is the result of the complex interaction between different geomorphic processes: splash erosion, sheet erosion, rill erosion, gully erosion, bank erosion as well as mass movements [10].…”