Document Type

Report

Publication Date

Winter 2024

Abstract

Wetlands serve as essential natural barriers, protecting coastal regions against the increasing threats from hurricane-induced storm surges, rising sea levels, and changing weather patterns. Understanding their structural resilience is crucial, particularly the shear strength of the wetland soil-root matrix, which contributes significantly to stability under extreme weather events. However, evaluating this shear strength is challenging due to the complex nature of root systems and the varying amounts of live biomass and necromass at different soil depths. This study utilized a Large-scale Direct Shear Apparatus (LDSA) to address this gap by assessing the shear strength of root biomass in a horizontal mode of shear, focusing on key plant species in U.S. coastal wetlands. The research was conducted in the Atchafalaya and Terrebonne Basins in Louisiana, selecting three distinct sites in each basin that span a salinity gradient from freshwater to saline marsh environments. This approach allowed for an investigation into how varying salinity levels influence the structural resilience of wetlands. The results demonstrated a marked upward curvature in the stress-displacement response, indicative of strain hardening within the soil-root matrix. This behavior is attributed to the intersecting longitudinal and diagonal roots within the shear plane, which significantly enhanced the soil's ability to resist shear stress. The findings emphasize the crucial role of vegetative roots in enhancing the resilience and stability of wetland ecosystems under stress. This research not only provides valuable insights into the biomechanical properties of wetland soils but also underscores the importance of integrating natural and nature-based features (NNBFs) in coastal protection strategies. The outcomes of this study are poised to guide future endeavors in coastal engineering and environmental management, advocating for holistic strategies that incorporate both the biological and geotechnical elements of wetland ecosystems for improved resilience and sustainability.

Comments

Tran-SET Project 22GTLSU25

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