The Theoretical Approach to the Modelling of Gully Erosion in Cohesive Soil

Aleksey Sidorchuk

doi:10.3390/earth3010015

Abstract

The stochastic gully erosion model (STOGEM) is based on a combination of deterministic mechanics and a stochastic description of the erosion control factors. The main proposition in the model is that the depth of the active surface layer of eroded cohesive soil is equal to one particle diameter, and the deposition of eroded particles is negligible. The erosion rate at the gully bed is calculated directly from the equation of the balance between driving and resistance forces acting on soil particles in flowing water using the probability density functions of stochastic variables: flow velocity, soil aggregate size and cohesion. Probability density functions of cohesion in the model vary through time and space during the erosion event due to the changes in soil composition—armoring and loosening. This theory is still far from achieving practical application, but opens up a new way for better understanding the experimental results of gully erosion and shows the direction for future investigations.

Highlights

IntroductionGullying is a form of linear erosion of loose and cohesive soils (and of rocks) by a concentrated water flow [1]
Gullying is a form of linear erosion of loose and cohesive soils by a concentrated water flow [1]
The relationships between the main factors of erosion and erosion rate are between the main factors of erosion and erosion rate are thetheoretically determined within the model for a given combination of input data

Summary

Introduction

Gullying is a form of linear erosion of loose and cohesive soils (and of rocks) by a concentrated water flow [1]. The larger linear forms are ephemeral gullies [2], which are usually destroyed by plowing, followed by typical gullies. This quantitative difference in the depth causes the main qualitative difference between active typical gullies and smaller linear erosion forms—the instability of gully walls. The processes of gully bed incision and bank erosion cause the increase in gully wall inclination and soil slumping and falling of different types. These processes are typical for the first stage of gully development. The gullies cut slopes to their whole potential (possible) length during this period, and their walls eventually stabilize

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