Laboratory data on wave propagation through vegetation with following and opposing currents

Abstract

Abstract. Coastal vegetation has been increasingly recognized as an effective buffer against wind waves. Recent laboratory studies have considered realistic vegetation traits and hydrodynamic conditions, which advanced our understanding of the wave dissipation process in vegetation (WDV) in field conditions. In intertidal environments, waves commonly propagate into vegetation fields with underlying tidal currents, which may alter the WDV process. A number of experiments addressed WDV with following currents, but relatively few experiments have been conducted to assess WDV with opposing currents. Additionally, while the vegetation drag coefficient is a key factor influencing WDV, it is rarely reported for combined wave–current flows. Relevant WDV and drag coefficient data are not openly available for theory or model development. This paper reports a unique dataset of two flume experiments. Both experiments use stiff rods to mimic mangrove canopies. The first experiment assessed WDV and drag coefficients with and without following currents, whereas the second experiment included complementary tests with opposing currents. These two experiments included 668 tests covering various settings of water depth, wave height, wave period, current velocity and vegetation density. A variety of data, including wave height, drag coefficient, in-canopy velocity and acting force on mimic vegetation stem, are recorded. This dataset is expected to assist future theoretical advancement on WDV, which may ultimately lead to a more accurate prediction of wave dissipation capacity of natural coastal wetlands. The dataset is available from figshare with clear instructions for reuse (https://doi.org/10.6084/m9.figshare.13026530.v2, Hu et al., 2020). The current dataset will expand with additional WDV data from ongoing and planned observation in natural mangrove wetlands.

Wave Breaking Induced by Opposing Currents in Submerged Vegetation Canopies

“…To apply the direct measuring method to derive C D , simultaneous velocity and force data were collected in all tests with various current‐wave combinations (Z. Hu et al., 2020). In addition to previous studies, we now include simultaneous velocity, force and C D when waves propagate with opposing currents (Figure S3 in Supporting Information ).…”

“…Although the proposed simple analytical model cannot precisely reproduce the WDV in each specific case but the general variation pattern with $$\alpha $$ can be well captured. Combining a detailed experiment data set (Z. Hu et al., 2020) and the analytical model, the present study is expected to improve our understanding of the wave dissipation capacity in wetlands, especially on the indirect WDV by breaking. The obtained knowledge and model may eventually serve future nature‐based coastal defense projects.…”

“…Such prediction is of critical importance to assess the resistance of coastal vegetation ecosystems under storm conditions (Simard et al., 2019). It is worth noticing that C D in the current study is averaged spatially across three locations in the canopy for simplicity, but the original data of F and u at each location is included in the open data set (Z. Hu et al., 2020) to facilitate further investigation on spatially varying forces. Finally, the current data set can also assist further investigations on the full variation of the C D with changing submergence ratio and stem densities (e.g., via machine learning), as the derived Equation does not account for all the variations in the current data set, especially when the Re is smaller than 1,000.…”

“…The experiment data presented in this study can be freely accessed at https://doi.org/10.6084/m9.figshare.13026530.v2 (Hu et al., 2020).…”

“…Additionally, various scenarios, including wave height and period, high and low stem densities as well as regularly and randomly arranged canopies were tested (Figure S1 in Supporting Information ). The obtained data of wave height, velocity and force on the vegetation stems are included in an open data repository (Z. Hu et al., 2020) to facilitate date reuse. A new analytical model is developed to explain the observed WDV with both direct and indirect contributions.…”