skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Soil Bioengineering Using Vetiver for Climate-Adaptive Slope Repair: Review
An increase in precipitation due to climate change has given rise to the number of landslide occurrences. Vetiver, which is a perennial grass, is becoming increasingly popular all over the world as a vegetation-based soil bioengineering tool for preventing landslides. Sunshine Vetiver grass, also known as Chrysopogon zizanioides is noninvasive and does not compete with other indigenous plants growing in the area. Even though it is a tropical grass, Vetiver can grow in a wide range of climate conditions, including those that are quite harsh in terms of both soil and climate. The roots can grow up to 3 m in length in a dense bushy root network under optimal conditions. In this review, the authors have studied the impact of Vetiver on landslide mitigation as a climate-adaptive slope repair tool based on the research undertaken so far. Furthermore, the authors have addressed the future potential and constraints associated with the use of Vetiver for landslide mitigation. It is seen that the use of Vetiver reduces pore water pressure. The high tensile strength of Vetiver roots provides reinforcement for slopes and enhances soil shear strength. Vetiver increases saturated hydraulic conductivity and reduces surface runoff and slip surface depth. Being a vegetation-based climate-adaptive technology, this grass exhibits great promise in its ability to effectively address landslide problems. However, the magnitude of the root impact diminishes as the depth increases, rendering Vetiver a more promising remedy for shallow landslide occurrences. In addition, Vetiver grass has a wide range of practical uses due to its unique characteristics, which provide additional benefits. Employment of Vetiver is cost-effective compared with traditional engineering methods, and it requires less initial maintenance, which implies that community-based initiatives can effectively address landslide prevention through Vetiver implementation  more » « less
Award ID(s):
2046054
PAR ID:
10584447
Author(s) / Creator(s):
;
Publisher / Repository:
American Society of Civil Engineers
Date Published:
Journal Name:
Natural Hazards Review
Volume:
25
Issue:
3
ISSN:
1527-6988
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, American Society of Civil Engineers)
    Beauregard, Melissa S; Budge, Aaron S (Ed.)
    Soil bioengineering using Vetiver is a widely used vegetation-based slope failure mitigation technique. Though Sunshine Vetiver grass, also known as Chrysopogon zizanioides, grows 3 m in length inside the soil in tropical and subtropical climate conditions, the depth up to which Vetiver impacts the soil property has remained undetected. This study has investigated the subsurface influence zone of Vetiver grass based on nondestructive geophysical investigations Electrical Resistivity Imaging (ERI) and Multichannel Analysis of Surface Waves (MASW) in a high plasticity expansive clay soil slope in Mississippi, United States. ERI data collected on the slope revealed that the top 2 m of the high plasticity clay soil had a higher resistivity value with Vetiver (ranging from 4 to 60 􀀺m) compared to the soil without Vetiver (ranging from 2 to 28 􀀺m). MASW investigation results at the same slope have indicated a similar increase in shear wave velocity with Vetiver up to 2 m indicating enhanced soil stiffness while compared to the section without it. The combined geophysical approach using ERI and MASW reveals that the root system of the Vetiver grass enhanced the moisture content and increased the stiffness of soil within the top layers. Though the grass roots can grow more than 3 m inside the soil, the major influence was observed within the top 2 m from the slope surface. 
    more » « less
  2. ; ; ; (, Geosciences)
    Due to cyclic wetting and drying, the hydro-mechanical behavior of unsaturated soil is impacted significantly. In order to assess the soil strength parameters, knowing the unsaturated behavior is important. Soil moisture content is an important parameter that can define the shear strength of the soil. Most of the highway slopes of Mississippi are built on highly expansive clay. During summer, the evaporation of moisture in the soil leads to shrinkage and the formation of desiccation cracks, while during rainfall, the soil swells due to the infiltration of water. In addition to this, the rainwater gets trapped in these cracks and creates perched conditions, leading to the increased moisture content and reduced shear strength of slope soil. The increased precipitation due to climate change is causing failure conditions on many highway slopes of Mississippi. Vetiver, a perennial grass, can be a transformative solution to reduce the highway slope failure challenges of highly plastic clay. The grass has deep and fibrous roots, which provide additional shear strength to the soil. The root can uptake a significant amount of water from the soil, keeping the moisture balance of the slope. The objective of the current study is to assess the changes in moisture contents of a highway slope in Mississippi after the Vetiver plantation. Monitoring equipment, such as rain gauges and moisture sensors, were installed to monitor the rainfall of the area and the moisture content of the soil. The data showed that the moisture content conditions were improved with the aging of the grass. The light detection and ranging (LiDAR) analysis was performed to validate the field data obtained from different sensors, and it was found that there was no significant slope movement after the Vetiver plantation. The study proves the performance of the Vetiver grass in improving the unsaturated soil behavior and stability of highway slopes built on highly expansive clay. 
    more » « less
  3. ; ; ; ; (, Geo-Congress 2022 GSP 336 268)
    With climate change frequency of extreme disasters is increasing day by day. Excessive rainfall causes shallow landslides during such extreme events, very commonly on highway slopes containing highly plastic clay. Mississippi results in a perfect area to study the Vetiver System (VS) performance for shallow slope failure under excessive rainfall, with an average annual rainfall intensity higher than other neighboring states in the south. A highway slope in Mississippi containing high-plastic clay is explored throughout the year 2019, where time-dependent slope movement along the depth is monitored with rainfall variation. A 9.1 m slope inclinometer along with a rain gauge and an air temperature sensor have been installed at that section. The slope has experienced a shallow movement at the slope surface with a depth of 1.9 m with already observed rainfall intensity. A 6 m2 area of the slope is selected and reinforced with Vetiver grass. Nevertheless, quantitative studies of how much contribution the VS provides to slope stabilization in the field are still relatively scarce. The current paper presents a comparative study of the VS performance on the shallow slope movement in expansive soil observed from inclinometer data for the last two years. It is observed that due to Vetiver grass, the slope movement rate has reduced to 2% since plantation of Vetiver grass from that of 10% before Vetiver grass. Later, this result is further verified through a numerical investigation where Vetiver grass is simulated by changing soil properties. Numerical analysis indicates root reinforcement from the root dimensions increases slope stability up to 30%. This study outlines an approach for the study of VS in terms of contribution to slope stabilization, including field observation and numerical analysis. 
    more » « less
  4. ; ; ; ; (, Journal of Ecology)
    Abstract In savannas, partitioning of below‐ground resources by depth could facilitate tree–grass coexistence and shape vegetation responses to changing rainfall patterns. However, most studies assessing tree versus grass root‐niche partitioning have focused on one or two sites, limiting generalization about how rainfall and soil conditions influence the degree of rooting overlap across environmental gradients.We used two complementary stable isotope techniques to quantify variation (a) in water uptake depths and (b) in fine‐root biomass distributions among dominant trees and grasses at eight semi‐arid savanna sites in Kruger National Park, South Africa. Sites were located on contrasting soil textures (clayey basaltic soils vs. sandy granitic soils) and paired along a gradient of mean annual rainfall.Soil texture predicted variation in mean water uptake depths and fine‐root allocation. While grasses maintained roots close to the surface and consistently used shallow water, trees on sandy soils distributed roots more evenly across soil depths and used deeper soil water, resulting in greater divergence between tree and grass rooting on sandy soils. Mean annual rainfall predicted some variation among sites in tree water uptake depth, but had a weaker influence on fine‐root allocation.Synthesis. Savanna trees overlapped more with shallow‐rooted grasses on clayey soils and were more distinct in their use of deeper soil layers on sandy soils, consistent with expected differences in infiltration and percolation. These differences, which could allow trees to escape grass competition more effectively on sandy soils, may explain observed differences in tree densities and rates of woody encroachment with soil texture. Differences in the degree of root‐niche separation could also drive heterogeneous responses of savanna vegetation to predicted shifts in the frequency and intensity of rainfall. 
    more » « less
  5. ; ; ; (, Natural Hazards Review)
    Bioinspired slope improvements can achieve outcomes similar to traditional slope improvements for shallow slope failures, while incorporating plant material as a structural component and using a minimum of heavy equipment. Vetiver grass can mitigate the rain-induced slope instability of earthen infrastructure, such as levees, constructed using loess and clay soils. Vetiver grassroots can extend to depths greater than 3 m (10 ft), creating a new composite material with the grassroots and soil, thereby increasing shear strength to combat shallow slope failures. The objective of this study is to determine the feasibility of vetiver as a climate-resilient bioinspired slope stability improvement on a test levee constructed of loess in Vicksburg, Mississippi (MS). Vetiver was planted at 1 ft center-to-center intervals on a 9.1 m wide (30 ft) section of an approximately 12.2 m long (40 ft) downstream slope of a test levee and observed for 2.5 years. To consider the effect of extreme precipitation events, a finite element analysis was completed for a comparable clay slope using 500 year precipitation intensity–duration– frequency curves of Jackson, MS. Precipitation negatively impacts the collapsible and expansive nature of the local loess and clay, respectively. The results demonstrate that vetiver grass is a viable method to increase slope stability for earthen levees constructed with loess and clay, which are prevalent in Vicksburg and Jackson, respectively. Vetiver also holds promise as a climate resilient solution to combat raininduced shallow slope failures. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email