Steep beach morphology changes due to energetic wave forcing
In: Marine Geology. Elsevier: Amsterdam. ISSN 0025-3227; e-ISSN 1872-6151, more
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| Author keywords |
beaches; beach erosion; GPS; nearshore |
| Authors | | Top |
- Dail, H.J.
- Merrifield, M.A.
- Bevis, M.
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| Abstract |
The three-dimensional variability of the sub-aerial beach is examined for Waimea Bay, Hawaii, a steep-slope pocket beach subject to energetic winter swell events. The beach is mapped using 32 Real-Time Kinematic Global Positioning System (RTK-GPS) surveys collected from March 1996 to July 1997. The survey method provides 4 m horizontal spacing and 2–3 cm vertical accuracy. The primary morphology change is the episodic removal and re-establishment of a foreshore dune during the winter swell season. The average sand volume flux between surveys reaches -8 and 4 m2/day during peak erosion and accretion periods. The sand volume of the sub-aerial beach is found to be highly correlated (0.96) with the position of the shoreline. Longshore variations in morphology include beach cusps with typical peak to trough amplitudes of 0.5–1.5 m and longshore wavelengths of 30–70 m. The relationships between the energetic swell forcing and the volume and flux of sand on the sub-aerial beach are examined. The highest correlation (-0.88) is found between the total sand volume and the wave energy flux after the latter is filtered following Wright et al. [Wright, L.D., Short, A.D., Green, M.O., 1985. Short-term changes in the morphodynamic states of beaches and surf zones: an empirical predictive model. Mar. Geol. 62, 339–364]. The filter is effective at capturing slow accretion phases following energetic erosion events. |
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