Departmental Papers (EES)

Document Type

Journal Article

Date of this Version

4-16-2013

Publication Source

Geophysical Research Letters

Volume

40

Issue

7

Start Page

1328

Last Page

1333

DOI

10.1002/grl.50323

Abstract

Sediment transport is an intrinsically stochastic process, and measurement of bed load in the environment is further complicated by the unsteady nature of river flooding. Here we present a methodology for analyzing sediment tracer data with unsteady forcing. We define a dimensionless impulse by integrating the cumulative excess shear velocity for the duration of measurement, normalized by grain size. We analyze the dispersion of a plume of cobble tracers in a very flashy stream over two years. The mean and variance of transport distance collapse onto well-defined linear and power-law relations, respectively, when plotted against cumulative dimensionless impulse. Data suggest that the asymptotic limit of bed load tracer dispersion is superdiffusive, in line with a broad class of geophysical flows exhibiting strong directional asymmetry (advection), thin-tailed step lengths and heavy-tailed waiting times. The impulse framework justifies the use of quasi-steady flow approximations for long-term river evolution modeling.

Copyright/Permission Statement

Copyright © 2013 by the American Geophysical Union.

Keywords

bed load transport, hydrograph unsteadiness, anomalous diffusion, sediment tracer particles

Share

COinS
 

Date Posted: 11 November 2016

This document has been peer reviewed.