Bed-Load Transport Rate Based on the Entrainment Probabilities of Sediment Grains by Rolling and Lifting

TL;DR

This paper introduces a new bed-load sediment transport rate model based on entrainment probabilities and travel lengths, showing improved accuracy over existing formulas and providing insights into grain movement dynamics.

Contribution

The paper develops a novel bed-load transport model using entrainment probabilities and introduces two travel lengths, enhancing prediction accuracy and understanding of sediment grain movement.

Findings

Model predictions align well with experimental data.

Total entrainment probability is a weighted sum of lifted and rolling grains.

Travel length for rolling grains is about ten times shorter than for lifted grains.

Abstract

A function for the bed-load sediment transport rate is derived. This is achieved from the first principle by using the entrainment probabilities of the sediment grains by rolling and lifting, and by introducing two travel lengths, respectively, for the first time. The predictions from the new bed-load function agree well with the experimental results over the entire experimental range and show significant improvement over the commonly used formula for bed-load transport rate. The new function shows that, in terms of contributing to the bed-load transport rate, the total entrainment probability of the sediment grains is a weighted summation of those by the lifted and rolling grains, rather than a simple addition of the two. The function has also been used to predict the total entrainment probability, saltation length and the bed layer thickness at high bed-load transport rate. These predictions all agree well with the experimental results. It is found that, on average, the travel length for the rolling sand grains is about one order of magnitude less than that for the lifted ones.