Influence of vetiver grass (Chrysopogon zizanioides) on infiltration and erosion control of hill slopes under simulated extreme rainfall condition in Bangladesh

Abstract

Rainfall events on hill slopes can cause both soil erosion and slope failures. With global climate change, the frequency of these events is increasing with greater consequences. Rainfall-induced erosion need to be studied in an integrated way to understand hill slope sediment yields. Among different methods for controlling erosion and slope stabilization, vegetation is widely used nowadays all over the world. Vetiver (Chrysopogon zizanioides) is a tropical grass which offers a practical and cost-effective way to prevent soil erosion. This deeply rooted and long-lived perennial grass has restrained erodible soils for decades. In this study, the effectiveness of vetiver grass in reducing soil erosion has been studied with a small-scale model study. Performance of slope against erosion was studied under rainfall for both bare slope and vetiver-rooted slope. A small-scale 1G physical model with a 40% slope was used to model bare and vegetated slope. Direct shear tests were conducted to evaluate the effect of vetiver roots on the shear strength of soil-root matrix. Rainfall was simulated using an artificial rainfall simulator with a rainfall intensity of 188 mm/h and Christiansen’s uniformity (CU) coefficient of 86.3%. The vegetated system reduced the surface runoff 18–71% for all vertical intervals compared to the control run. The infiltration capacity of the vegetated slope was evaluated with respect to different infiltration models. The results of the present study were found in close agreement with Kostiakov’s infiltration model.