The Role of Vegetation on Debris Slope Stability (Case study: Tuskestan–Chaharbagh Road, Golestan Province)

Document Type : Complete scientific research article

Authors

1 Gorgan University of Agricultural Sciences & Natural Resources, Dept. of Watershed Management, Gorgan,

2 Gorgan University of Agricultural Sciences & Natural Resources, Dept. of Arid Zone Management, Gorgan,

3 Gorgan University of Agricultural Sciences & Natural Resources, Dept. of Rangeland Management, Gorgan,

4 Department of Forestry, Faculty of Forest Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

Abstract

Background and Objectives: Today, the instability of the debris slopes is a huge problem that human has been facing due to maladministration and overexploitation of existing resources. One of these methods is to apply the Vegetation because of features such as bioengineering capabilities, economical issues, bio-technical issues and high durability, self-regeneration, self-renewal and no negative impacts on the environment at slope stability.The purpose of this study is to investigate the role of plant species in the stability of debris slopes of Tuskestan-Chaharbagh road as a bioengineering approach.

Materials and Methods: To do so, firstly, the study area was investigated and 35 locations (14 locations were stable and 21 locations were debris) were selected for sampling from plants and soil. The sampling of roots was done at the depth of 0-30 cm of the dominant species at each slope and the sampling of soil was conducted at the depth of 0-20 cm. The density and canopy percentage of the vegetation at the grasslands and forests were measured respectively with square plots (1 m2) and circular plots (100 m2). Some of the soil characteristics such as: shear strength, cohesion, internal friction angle, humidity, aggregate stability, slope, gradation curves (the percentage of fine-grained and course-grained particles) and the root tensile strength of the dominant species were measured at some of the slopes. The study was tested by the Independent T- test at the SAS software.

Results: The results of the experimentations showed that the average mean of the above parameters on the stable and debris slopes were: 0.1739_15.82 kg/cm2 for shear strength, 0.0996_0.0999 kpascal for cohesion, 11.071_0.928 % for humidity, 0.4343_0.4588% for aggregate stability, 35.5_43 % for slope and 183.34_108.93 megapascal for root tensile strength. Vegetation also had meaningful impacts on the above parameters at the 5% level and it should be added that the density and canopy percentage of vegetation, were more at stable slopes in comparison wit the debris slopes. The dominant rangeland species (Melica persica) and (Astragalus sp) at the stable slopes and specie (Tussilago farfara) at the debris slopes. On the other hand, dominant tree specie (Carpinus betulus) at the stable slopes and shrub species (Rubus sp) at the debris slopes. The species (Melica persica) and (Astragalus sp), with the highest density average of grassland herbaceous and bush plants with the highest average of canopy percentage and also the tree species (Carpinus betulus) with the highest average of canopy percentage, has had the most impact on the slopes stability and soil conservation and on the conterary. On the other hand, the specie of (Crataegus monogyna) with the highest density average of shrubs plants and the highest average of canopy percentage, has had the most impact on the slopes instability.

Conclusion: It could be also concluded that a vegetation with a high density and canopy percentage leads to the increase of shear strength, internal friction angle, course-grain percentage, soil humidity and root tensile strength and causes a decline at cohesion, fine-grain percentage, aggregate stability and slope at the stable slopes in comparison with the debris slope and therefore results in the fixation of the slope. Therefore, vegetation is considered as bioengineering method for the fixation of the debris slopes.

Keywords

References

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Journal of Water and Soil Conservation
Volume 27, Issue 5
January and February 2021
Pages 185-200

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