Search Results (3)

This paper presents the observed morphological evolution of a multilevel beach cusp system in Long Strand, Co. Cork, Ireland. The surveys were carried out with an Unmanned Aerial Vehicle (UAV) system between March and September 2019. From this site, three levels of beach cusps on the beachface (i.e., lower beach level, mid beach level and upper beach level), and critical cusp parameters are reported, including cusp spacing, cusp elevation, cusp depth, and cusp amplitude. Thus far, such an extensive dataset has not previously been reported in the literature from a single site. The evolution of the different cusp parameters is then linked with the hydrodynamics in the study area, and new prediction theories are proposed for the different cusp parameters. The Lower beach level cusps (1 < z < 2.5 m Irish Transverse Mercator (ITM)) changed with every tide and appeared when surf-similarity parameter-ξ₀ < 1.55. These cusps had a mean cusp spacing of λ_mean = 11.09 m, which are closely linked with the predictions of the self-organisation theory (p < 0.05). In contrast, the Mid beach level cusps (2.5 < z < 3.5 m ITM) are less dynamic compared to the Lower beach level cusps and can persist between spring tidal cycles. They had a mean cusp spacing of λ_mean = 18.17 m. The Upper beach level cusps (approximately z = 6 m ITM) are above astronomical tide levels and have a mean cusp spacing of λ_mean = 40.26 m. They did not change significantly over the survey period due to a lack of major storm events. These findings give a better understanding of the evolution of different cusp parameters for a multilevel beach cusp system and can be used to formulate a global theory regarding their change over time. Full article

Unusual shore-normal and barred-like rhythmic features were found in Camposoto Beach (Bay of Cádiz, SW Spain) during a monitoring program using unmanned aerial systems (UAS). They appeared in the backshore and persisted for 6 months (October 2017–March 2018). Their characteristics and possible formation mechanism were investigated analyzing: (1) UAS-derived high-resolution digital elevation models (DEMs), (2) hydrodynamic conditions, and (3) sediment samples. The results revealed that the features did not migrate spatially, that their wavelength was well predicted by the edge wave theory, and that they shared characteristics with both small-scale low-energy finger bars (e.g., geometry/appearance and amplitude) and swash cusps (e.g., wavelength, seaward circulation pattern, and finer and better sorted material in the runnels with respect to the crests). Our findings pinpoint to highly organized swash able to reach the backshore during spring tides under low-energy and accretionary conditions as well as backwash enhanced by conditions of water-saturated sediment. This study demonstrates that rhythmic features can appear under different modalities and beach locations than the ones observed up to date, and that their unusual nature may be attributed to the low spatiotemporal resolution of the traditional coastal surveying methods in comparison with novel technologies such as UAS. Full article

In this study a video-monitoring system was used to analyze the presence of mesoforms during a time period of five years in the urban beach of La Victoria, Cádiz, Spain. This technique allowed the generation of plan views using an improved version of ULISES software. The presence and spatiotemporal variability of the most common mesoforms, such as bars and cusps, was identified in all the plan views. Furthermore, the morphodynamic state of the beach was investigated in combination with local hydrodynamic data. The cusp systems were also studied by means of wavelet analyses and different theories on cusps formation were tested. The presence of the investigated features was related to the wave energy and its seasonal variations. The behavior of the mesoforms demonstrated the important role of a subtidal rocky outcrop in the nearshore processes. The results also show that bars and cusps as indicators of the nearshore processes are a useful tool for the macroscopic analysis of surf zone dynamics in dissipative beaches. Full article