Effects of plant root density on the erodibility of lateritic topsoil by simulated flume experiment

A laboratory facility was built to quantify effects of grass roots on the erodibility of lateritic topsoil by concentrated flow erosion. The design allowed slope gradient and flow rate to be controlled. The hydraulic flume was used to test the concentrated flow erosion from three lateritic topsoils (bare, scatter grass-root-permeated and densely grass-root-permeated) and exposed to two slopes (25 and 35%). The aim of the test was to formulate a model to represent effect of grass roots density on topsoil erosion by concentrated flow for lateritic topsoil of Paschim Medinipur, West Bengal, India. The detachment rates of undisturbed topsoil samples collected from twenty ( three bare soil, eight scatter grass and nine densely grasses) soil monitored through a 1.82 m long, 0.094 m wide hydraulic flume under two different slope condition (25 and 35%). Velocity of flow was set at 0.000492 and 0.00064 m3s-1 and flow shear stresses (τ,) ranged between 3.8 and 17.5 Pa. The results indicated that a significant negative exponential relationship between relative soil detachment (RSD) and roots density (RD) was detected. This study yielded one prediction equation that allowed comparison of their efficiency in assessing soil detachment rate in concentrated flow. The equation including the root density (RD) shows a better correlation coefficient (R2 = 0.73067). It may be concluded that the formula based on root density (RD) has the potential to improve methodology for assessing soil detachment rate in concentrated flow for lateritic topsoils.