ESTABLISHMENT OF JET INDEX Ji FOR SOIL ERODIBILITY COEFFICIENTS USING JET EROSION DEVICE (JEd)

Abstract

Soil erodibility has been identified as one of the major factors that govern threshold of
resistance to erosion. Accurate measurement of soil erodibility in the field is indeed important for the
determination of critical shear stresses. Critical shear stress is the stress that initiates particle movement that
promotes shifting of the bankline. An attempt to establish soil erodibility parameters was successfully carried
out using a newly fabricated Jet Erosion Device (JEd) based on soil properties. Soil erodibility coefficients
are introduced to represent the erodibility of the soils under study. Statistical test is used to confirm the
validity and accuracy of the proposed technique. Field data measurements were carried out on 3 rivers.
Empirical models were developed using data from Selangor River and validated using data from Bernam and
Lui rivers and other secondary river data. Analyses have shown high correlations and the parameters were
further examined and analysed for the development of a predictive relationship for Ji. The most accurate
model was selected based on the adjusted R2, standard error of the estimate and discrepancy ratio to illustrate
its significance. Selection of the predictive variables was based on their ability to explain the variation of Ji.
The models established could significantly reduce the cost, time and usage of water supply for field data
collection using JEd.