Session: Government Agency Student Posters

Paper Number: 173101

Physical Modelling of Vetiver Grass Performance Under Extreme Rainfall Conditions for Evapotranspiration 

Climate change has significantly intensified the frequency and magnitude of extreme precipitation events worldwide, posing unprecedented challenges to transportation infrastructure stability. Highway embankments and cut slopes are particularly vulnerable to these extreme weather conditions, experiencing increased surface runoff, elevated pore water pressure, and accelerated soil failure mechanisms that compromise structural integrity and public safety. Traditional slope stabilization methods, while effective, often involve substantial costs and environmental impacts, necessitating the exploration of sustainable, nature-based solutions that can provide long-term resilience while offering ecological co-benefits.

This comprehensive study investigates the bio-engineering effectiveness of vetiver grass (Chrysopogon zizanioides) as a nature-based solution for stabilizing shallow highway embankments under extreme rainfall conditions. Vetiver grass was selected for its exceptional characteristics, including an extensive fibrous root system that can penetrate up to 3-4 meters deep, high tensile strength roots providing mechanical soil reinforcement, and superior drought tolerance with efficient water uptake capabilities. The experimental investigation utilized designed laboratory-scale lysimeters constructed with Yazoo clay, a highly expansive soil prevalent throughout Mississippi's highway infrastructure. This soil type contains significant quantities of montmorillonite clay minerals, causing dramatic volumetric changes with moisture fluctuations—swelling substantially during wet periods and shrinking extensively during dry conditions, creating critical stability challenges for roadway infrastructure.

The experimental framework incorporated three distinct slope configurations to assess geometry effects on bio-engineering performance: Frame 1 featuring a steep 1H:1V slope, Frame 2 with a moderate 2H:1V slope, and Frame 3 with a gentle 3H:1V slope. Each lysimeter featured sophisticated design elements including a 0.5 mm geomembrane liner for precise moisture control and infiltration management, geotextile separation layers preventing contamination between the drainage base layer and overlying clay, and a strategically positioned 3-inch toe drain system ensuring controlled surface drainage.

Controlled rainfall simulation was implemented using a 100-year return period intensity of 18.79 mm/hour, according to National Oceanic and Atmospheric Administration standards for extreme precipitation events specific to the southeastern United States region. Advanced monitoring infrastructure comprised installed soil moisture content sensors and matric potential sensors positioned at 0.5 m and 1.5 m depths throughout each lysimeter, providing continuous real-time data acquisition of subsurface hydrological conditions and soil-water interactions. Vetiver grass was systematically planted across slope surfaces with density variations optimized for each slope geometry configuration to maximize root reinforcement effectiveness.

Comprehensive data collection included high-resolution pre- and post-rainfall LiDAR scanning to quantify detailed topographical changes and assess surface erosion patterns. Advanced finite element modeling using Plaxis software enabled detailed analysis of saturation distribution, suction stress development, and evapotranspiration processes throughout the soil profile. This systematic experimental approach provides quantitative evaluation of slope geometry influences on rainfall infiltration patterns, evapotranspiration efficiency, and the overall bio-engineering effectiveness of vetiver grass in shallow embankment stabilization applications. The research significantly advances understanding of evapotranspiration's critical role in landslide prevention and provides evidence-based guidance for implementing cost-effective, sustainable vegetation-based slope stabilization solutions capable of withstanding increasingly severe climate-induced extreme weather events.

Keywords: Landslide, Slope stabilization, Nature-based solutions, Vetiver, Evapotranspiration

Presenting Author: Richa Pokhrel Jackson State University

Presenting Author Biography: Richa Pokhrel is a Master's student in the Department of Civil and Environmental Engineering at Jackson State University, where she serves as a Graduate Research Assistant under the supervision of Dr. Sadik Khan. Her primary research focus centers on developing and evaluating nature-based solutions for landslide repair and slope stabilization, with particular emphasis on bio-engineering approaches that integrate sustainable vegetation systems for infrastructure resilience.

Authors:

Richa Pokhrel Jackson State University
Rahul Biswas Jackson State University
Asef Israk Arnob Jackson State University
Sadik Khan Jackson State University