The role of fringing coral reefs on beach morphodynamics

• Published in: Geomorphology (Amsterdam, Netherlands) Vol. 198; pp. 69 - 83
• Main Authors: Ruiz de Alegria-Arzaburu, Amaia, Mariño-Tapia, Ismael, Enriquez, Cecilia, Silva, Rodolfo, González-Leija, Mariana
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-09-2013; Elsevier
• Subjects: Beach morphodynamics; beaches; coral reefs; corals; Earth sciences; Earth, ocean, space; Empirical orthogonal functions (EOF); energy flow; Exact sciences and technology; Fringing coral reefs; Geomorphology, landform evolution; Marine and continental quaternary; Roughness; sand; sediment transport; shorelines; Surficial geology; water power; Wave dissipation; Wave modelling (SWAN); Caribbean; Mexico; North Atlantic; Caribbean Sea; Atlantic Ocean; Northwest Atlantic; North American Atlantic; Wave dissipation; Beach morphodynamics; Empirical orthogonal functions (EOF); Wave modelling (SWAN); Fringing coral reefs; Roughness; shorelines; degradation; North America; beaches; roughness; energy; waves; fringing reefs; models; corals; morphology; vulnerability; offshore; energy dissipation; sand; sediment transport; spatiotemporal variations; Invertebrata; invertebrates; landform evolution
• ISSN: 0169-555X; 1872-695X
• DOI: 10.1016/j.geomorph.2013.05.013

This paper examines the degree of energy dissipation provided by a fringing coral reef, and its role on the morphodynamics of adjacent beaches in terms of volumetric sediment transport. Morphological data were collected from the microtidal Mexican Caribbean beaches of Puerto Morelos, fringed by a reef, and Cancun, without a reef, from September 2007 to May 2011. Being exposed to the same offshore wave conditions, the morphodynamics of the coral reef-fronted beach were compared with those of the adjacent beach without a coral reef. Spatio-temporal changes in beach morphology were determined applying empirical orthogonal functions (EOF) to the shorelines extracted from the topographic data, and it was concluded that Puerto Morelos was considerably less dynamic than Cancun. The longshore energy fluxes were larger in Cancun, and the subaerial morphological differences in both beaches and under the same offshore conditions demonstrated that Puerto Morelos was particularly stable under shore-normal easterly waves. A calibrated phase-averaged wave model was implemented to determine the amount of wave energy dissipation across the coral reef. For energetic shore-normal waves the model determined that the semi-emerged coral reef was capable of reducing up to 85% of the incident wave height. The reef-crest height controlled the amount of wave energy dissipation, and the distance between the reef-crest and the shore determined the vulnerability of the beach to morphological changes. Reef-crest degradation by 1m resulted in a 10% increase in incoming wave energy, which resulted in 0.9m3/h/m of sand being mobilised along the beaches closer to the reef.
•Reef induced energy dissipation and its role on beach morphodynamics is evaluated.•The reef-fronted beach is considerably less dynamic than that without a reef.•For energetic normal waves the reef reduces up to 85% of the incident wave height.•The reef-crest height largely controls the amount of wave energy dissipation.