Print Email Facebook Twitter Experimental investigation of wave attenuation by mangrove forests with submerged canopies Title Experimental investigation of wave attenuation by mangrove forests with submerged canopies Author Zhang, R. (Hohai University; State Environmental Protection Key Laboratory of Marine Ecosystem Restoration) Chen, Y. (Hohai University) Lei, Jiaxin (Hohai University) Zhou, Xin (Hohai University; Ministry of Land and Resources of China) Yao, P. (Hohai University) Stive, M.J.F. (TU Delft Coastal Engineering) Date 2023 Abstract Mangroves can function as a ‘bio-shield’ to protect coastal communities from harsh environments because of their strong ability to attenuate wave energy. However, as mangroves are usually oversimplified as rigid cylinders in antecedent studies, the effects of complex mangrove morphology on wave attenuation have not been well researched. Although increasing attention has been paid to the wave dissipation induced by varying mangrove morphologies, most of them focus on the bottom trunk and root components of mature mangrove trees. There are few investigations about the contributions of the canopies of young saplings and/or short species to wave attenuation. To bridge this knowledge gap, a series of laboratory experiments under regular waves were conducted to examine the hydrodynamic variations affected by varying mangrove morphology configurations. Three water depths were considered to explore the influences of the vertical-varying submerged volume of mangroves when the artificial mangrove models are submerged, nearly emergent, and fully emergent. The mangrove forest model is 2 m long at a 1:10 scale. Three mangrove configurations, i.e. with no canopy, sparse canopy, and dense canopy were applied and compared to isolate the wave attenuation contributed by mangrove canopies. The results highlight the wave energy attenuation attributed to the canopy density. A linear correlation is found between the wave damping factor and a new variable named hydraulic submerged volume index (HSVI). The bulk drag coefficient, including canopy effects, was calculated to characterize mangrove-induced wave attenuation when the mangrove canopy is submerged. The relationships between the bulk drag coefficient CD and the characteristic hydraulic numbers (i.e., Reynolds number, Keulegan–Carpenter number, Ursell number) are discussed in detail. Consequently, new generic formulas of CD were deduced considering the effects of the submerged canopy. The employment of new CD formulas improves the reliability of the prediction of the wave attenuation ability by mangroves since the canopy effects are incorporated. Subject Drag coefficientExperimental analysisSubmerged mangrove canopiesWave attenuationWave damping factor To reference this document use: http://resolver.tudelft.nl/uuid:9e066479-d288-4a8a-b962-5a312e56f337 DOI https://doi.org/10.1016/j.coastaleng.2023.104403 Embargo date 2024-03-23 ISSN 0378-3839 Source Coastal Engineering, 186 Bibliographical note Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2023 R. Zhang, Y. Chen, Jiaxin Lei, Xin Zhou, P. Yao, M.J.F. Stive Files PDF 1_s2.0_S0378383923001278_main.pdf 7.5 MB Close viewer /islandora/object/uuid:9e066479-d288-4a8a-b962-5a312e56f337/datastream/OBJ/view