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Recently, bulk drag coefficient (~CD) formulations used to quantify wave energy dissipation by Rhizophora mangroves were developed from laboratory data; however, these formulations have not yet been validated with field data. Additionally, due to the complex geometry of mangrove trees within forests and spatial variability, common criteria for determining the adequate geometric characteristics of mangrove forests are lacking and are required to obtain accurate definitions for ~CD. This paper addresses these knowledge gaps by proposing a newly integrated ~CD formulation based on the comprehensive characterization of a Rhizophora mangle forest combined with wave measurements in field, and by using numerical modeling for the calibration process. The field campaign consisted of 23 continuous days of recorded wave data and spatial distribution observations of the geometric characteristics of the mangrove forest. The variation in frontal area per unit height per square meter (Ahm) along the mangrove forest was reported for three zones with different densities identified along the study transect, with decreasing root density from the vegetation edge to the forest interior. On average, the incident wave height decreased by 34% at 63 m in mangrove forests, and the wave attenuation ratios (r) varied between 0.001 and 0.01 m-1. To estimate the ~CD values associated with these wave height attenuation ratios, the Simulating Waves Nearshore (SWAN) numerical model was used to calibrate the model results with the field observations. The variation in the tree frontal area along the mangrove forest and the wave conditions at the site are considered during the calibration process. To further characterize ~CD for this type of mangrove species, the ~CD values acquired from the calibration together with the values reported in the literature from laboratory experiments are presented as a function of the Keulegan-Carpenter number (KC). Root diameter is defined as the characteristic length according to the inherent geometric characteristics of a Rhizophora sp. forest. The new formulation allows us to predictably estimate ~CD values that can be used as inputs in drag force-based models to estimate the attenuation of wave energy produced by Rhizophora sp. forests. [ABSTRACT FROM AUTHOR]

Most existing analytical and numerical models to quantify wave energy attenuation attributed to saltmarshes are based on the definition of a drag coefficient that varies with vegetation and wave characteristics and requires calibration, i.e., a case-specific variable. With the aim of determining a new variable to estimate wave energy attenuation without the use of calibration coefficients, wave attenuation caused by different saltmarsh species and the relationship with the ecosystem standing biomass are experimentally studied. Samples of four real saltmarshes with contrasting morphological and biomechanical properties, namely, Spartina sp., Salicornia sp., Halimione sp. and Juncus sp., are collected in the field and placed in a wave flume for testing under different regular and random wave conditions. Two meadow densities are considered, in addition to zero-density cases. Thus, wave damping coefficients are obtained in vegetated cases, β, and bare soil cases, βB, and wave damping produced solely by the meadow standing biomass, βSB, is determined. The obtained wave damping coefficients are related to a new variable, the hydraulic standing biomass (HSB), which is defined as a function of the meadow mean height and standing biomass and incident flow characteristics. Linear fitting relationships between the wave damping coefficient and HSB are obtained, allowing β and βSB estimation without the need for calibration. Therefore, the use of these new relationships facilitates direct quantification of wave energy attenuation due to saltmarshes based on incident wave conditions, mean plant height and meadow standing biomass, variables that can be obtained from aerial images or remote sensing data, extending the applicability of the approach. Another key aspect is that this approach does not depend on any calibration coefficient and can be directly applied with knowledge of the abovementioned characteristics. This may represent a paradigm shift in the estimation of wave energy attenuation attributed to saltmarshes. [ABSTRACT FROM AUTHOR]

Several numerical tools have been developed to quantify the wave height decay through vegetation, such as saltmarshes. Among them, one of the most widely used is SWAN (Simulating Waves Nearshore), where Suzuki et al. (2012) implemented and validated Mendez and Losada (2004) formulation. The reliability of this approach is based on a good estimation of plant traits and the suitable choice of the bulk drag coefficient C ˜ D , which is usually used as a calibration coefficient. Recently, Maza et al. (2022) described a new predictive approach to quantify wave attenuation by saltmarshes without the need for calibration coefficients. They estimate the wave damping coefficient (β) as a function of the Hydraulic Standing Biomass (HSB), a parameter defined as a function of the standing biomass, the mean height of the meadow and the wave incident conditions. In this work, Maza et al. (2022) formulation is implemented in SWAN, and validation with laboratory and field data is carried out for six saltmarsh species, showing the good performance of SWAN without calibration. Additionally, the model is extended for including standing biomass and plant height spatial variation to consider the natural variability of the vegetation characteristics along a transect from the lower-marsh to the upper-marsh. Finally, it is shown that the new implementation presents significant advantages in the modeling of wave height evolution along different saltmarsh fields when compared with the standard drag-based approach applied by using existing empirical formulations. • New numerical implementation in SWAN for quantifying wave height attenuation by saltmarshes based on standing biomass. • The new predictive tool has been validated for six saltmarsh species with different geometrical and biomechanical properties. • The spatial variability in vegetation traits along the saltmarsh field is considered in model validation. • The new numerical implementation does not rely on the definition of any calibration coefficient. • The comparison between drag approach and the new presented approach highlights the advantages of using the new approach. [ABSTRACT FROM AUTHOR]

A three dimensional numerical approach based on IHFOAM to study the interaction of tsunami waves with mangrove forest is presented. As a first approximation, the problem is modelled by means of solitary waves impinging on emergent rigid cylinders. Two different conceptual approaches are implemented into IHFOAM. Solving the URANS equations provides a direct simulation of the flow field considering the actual geometry of the array of cylinders. A modified version of the volume-average URANS equations by introducing a drag force to model the momentum damping created by the cylinders is used in the second approach. Both the direct and macroscopic simulations are validated against laboratory experiments for wave damping with very high agreement. A large set of numerical experiments to analyse flow parameters and uniform and random cylinder array distributions are analysed and use to compare pros and cons of the different approaches. Large differences are found in the forces exerted on the vegetation for uniform and random distributions. Generalizations obtained from uniform arrangements could lead to underestimation of wave-exerted forces, especially for low dense configurations. Wave forces calculated with the macroscopic approach by means of the drag coefficient yields clear underestimations. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a new model for wave and submerged vegetation which couples the flow motion with the plant deformation. The IH-2VOF model is extended to solve the Reynolds Average Navier–Stokes equations including the presence of a vegetation field by means of a drag force. Turbulence is modeled using a k–ε equation which takes into account the effect of vegetation by an approximation of dispersive fluxes using the drag force produce by the plant. The plant motion is solved accounting for inertia, damping, restoring, gravitational, Froude–Krylov and hydrodynamic mass forces. The resulting model is validated with small and large-scale experiments with a high degree of accuracy for both no swaying and swaying plants. Two new formulations of the drag coefficient are provided extending the range of applicability of existing formulae to lower Reynolds number. [Copyright &y& Elsevier]

Semi-analytical solutions are proposed to investigate the effects of a submerged/suspended circular patch on water waves scattering. The patch is simplified to periodic cylindrical lattices with a strong contrast between the cylinder spacing and the typical wavelength. The homogenization theory is employed to derive the effective equations on the macro-scale (wavelength), in which the constitutive coefficients are obtained by numerically solving the micro-scale (cylinder spacing) problem in a unit cell. To simulate the turbulence in the circular cylinder patch, a bulk eddy viscosity model is applied through balancing the time-averaged energy over a wave period. Eigenfunction expansions method is used to solve the macro-scale problem, where a complex frequency dispersion relation is solved by the multiple successive approximation technique. Comparisons between the laboratory measurements and the waves/submerged circular patch model results show acceptable agreements for small amplitude waves. The waves/suspended circular patch model is not checked experimentally due to the lack of data. However, this suspended patch model is shown to reproduce the results of wave/emergent circle forest problem. A comprehensive comparison between the submerged, suspended and emergent circular patches on wave scattering is also presented. • Semi-analytical solutions are presented for water waves scattering by a submerged/suspended circular patch as the main creatively work of this study. • The present solutions have been checked with laboratory measurements and other solutions from previous studies. • The solutions are simple and allow straightforward numerical implementations. No additional fitting coefficient is needed in the model computation. • A comprehensive analysis on wave scattering by different forms of circular patches has been discussed. [ABSTRACT FROM AUTHOR]