Wave hydrodynamics around a multi-functional artificial reef at Leirosa

Abstract

This paper describes an application of the Boussinesq-type COULWAVE model to study the wave hydrodynamics in the vicinity of a multi-functional artificial reef (MFAR). This reef is under investigation and consists of a supplementary protection solution for the Leirosa sand dune system located at South of Figueira da Foz, on the Portuguese West coast. Such installation near the coastline is expected to contribute to enhance the surfing conditions in the area, protect the sand dune system in the surroundings of Leirosa beach, and increase its environmental value. Numerical calculations with the COULWAVE model were performed for four test cases, considering two reef geometries (differing in the reef angle) and two incident wave conditions (storm condition and a common wave condition). Comparisons between the results obtained, in terms of wave heights and breaking line positions allow us to assess the influence of the reef on the hydrodynamics near the beach and around the reef. Moreover, the reef performance was analysed in terms of surfability and coastal protection. The surfability parameters (breaker height, Iribarren number and peel angle) were calculated for each test case using the numerical wave heights, wave directions and wave breaking positions. Comparisons of parameters allow characterizing the most appropriate configuration of the reef to improve the surfing conditions in the study area. A methodology based on numerical free surface elevations and horizontal velocity components was developed to calculate wave directions, since this is not a direct output of the COULWAVE model. Concerning coastal protection, analyses of the mean currents around the reef were used together with observations of the velocity cells near the shoreline as an indication of the sediment transport.

Macrofaunal community abundance and diversity and talitrid orientation as potential indicators of ecological long-term effects of a sand-dune recovery intervention

“…Nevertheless, a specific morphodynamic study should be required (Mendonç a et al, 2012), to assess the erosive rates at both the sites, in order to exactly evaluate whether the observed differences are ascribable to the dune-recovery Table 6 Summary circular statistics for the orientation experiments on T. saltator at the two sites (p0 = natural dune, p1 =artificial dune) for the period of the study (2011)(2012) intervention. In other words, p1 became a more dissipative beach with respect to p0 that showed a more reflective typology (McLachlan and Brown, 2006).…”

Modeling of Wave Propagation from Arbitrary Depths to Shallow Waters – A Review

“…Figure 5 also shows for all cases that convergent cells appear, indicating a possible sedimentation near the shoreline, suggesting that the chosen geometries (Figure 4) are advantageous for both coastal protection and improving surf conditions. Anyway, as referred in [28], a morphological study should be done in order to confirm these results.…”

“…The characteristics of the simulations for the different cases are described in Table 1. As recorded in [28], "the computational domain is around 1870 m in the long-shore and 1670 m in the cross-shore direction with a constant node spacing of around Δx = Δy =2.0 m and a Courant number of 0.5. The total simulation time was 800 s. A flat bottom is placed in front of the slope where waves are generated using the source function method ( [39] Wei et al, 1995).…”

A Comparison of Beach Nourishment Methodology and Performance at Two Fringing Reef Beaches in Waikiki (Hawaii, USA) and Cadiz (SW Spain)

“…In fact, some studies have taken into account the former geologic setting to design multifunctional artificial reefs that serve several purposes [8].One common type of geologically-controlled beach is situated landward of areas of hard bottom, such as rock or coral reefs. Reefs have large impacts on coastal hydrodynamics, sediment transport, and morphology, such as by influencing water level fluctuations [9], wave set-up and cross-reef currents [10], wave breaking, wave-induced flows, and wave attenuation over reef platforms [11][12][13][14][15], which affect the beach morphodynamics tidal range at multiple scales [16][17][18][19], even under hurricane conditions [20,21].Despite clear evidence that beaches with reefs behave differently to their non-reef counterparts, there has been scant attention given to how reefs should be considered in beach nourishment projects. A recent study by Habel et al [22] focused on the methodology of a beach nourishment at Royal Hawaiian Beach (RHB), Waikiki, which is fronted by a fringing coral reef.…”

“…One common type of geologically-controlled beach is situated landward of areas of hard bottom, such as rock or coral reefs. Reefs have large impacts on coastal hydrodynamics, sediment transport, and morphology, such as by influencing water level fluctuations [9], wave set-up and cross-reef currents [10], wave breaking, wave-induced flows, and wave attenuation over reef platforms [11][12][13][14][15], which affect the beach morphodynamics tidal range at multiple scales [16][17][18][19], even under hurricane conditions [20,21].…”