ABSTRACT

This study investigated the energy attenuation by a vegetation patch against the extreme flow by considering two flow models (Solitary wave and dam-break generated flow) from the literature that represent the tsunami-like flow. The protection level provided by a vegetation belt is observed to be under-predicted when solitary waves are considered to represent the tsunami. The maximum percentage of energy reduction observed for the solitary flow model in the present study was about 13.07 %. Yet the maximum energy reduction provided by the same vegetation patch considering an inundating bore generated by a dam break was about 79.59 %. The significant difference in the energy reduction between the two models is due to the fact that the energy dissipation process is different for the two flow models – solitary and inundating bore. The energy dissipation is anticipated due to pressure drag in the former and hydraulic jump in the latter. There is no reduction in the time of arrival of the flow with the presence of a vegetation belt in both flow models.

INTRODUCTION

The coastal vegetation is being proposed as a natural protection measure ("Bio-shields"), considering the protections provided during the extreme storms and tsunami events of the past. Field studies from the Indian Ocean Tsunami (2004) have proven the significance of vegetation in protecting the hinterland (Danielsen et al., 2005; Kathiresan & Rajendran, 2005; Mascarenhas & Jayakumar, 2008; Sundar et al., 2007). The mangroves along the north coast of Singapore were observed to be effective wave attenuators (Lee et al., 2021). Accounting for the efficacy of the vegetation, review articles on protection measures of coastal vegetation, parameters influencing wave-vegetation interaction processes, and modelling approaches were compiled (Hari Ram & Sundar, 2024; Maza, 2024; Paul, 2024). Besides, coastal vegetation provides other benefits, such as reducing soil erosion (Besset et al., 2019; Montakhab et al., 2012; Thampanya et al., 2006). And global warming effects through carbon sequestration (Bianchi et al., 2013; Ward, 2020)

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