STEP 2: EXPERIMENTAL RESULTS
Dr. Santiago Gajá Ferrer
Bachelor’s Degree: Oceanology, School of Marine Sciences, UABC Ensenada
Master's degree: Physical Oceanography, ICMyL-UNAM
Doctorate: Civil Engineering (coasts and ports), IINGEN-UNAM
From a scientific point of view, research is being carried out to find an explanation for the formation of these diamond or rhombic-like patterns (micro-morphological characteristics of beaches), based on the physical phenomena involved in coastal hydrodynamics and morphological characteristics of the beaches, with greater attention to the interaction of the turbulent layer of water generated by the breaking of the waves (in the "swash" zone) and the transportation of sediment or layer of superficial sand on the beach. The study of this interaction focuses on the re-suspension of the sediment by the turbulent layer and the deposit of it during the phenomenon known as "backwash". The hypothesis is that the direction of the turbulent water currents towards the beach called "uprush" and the direction of the water towards the ocean called "backwash", play an important role in the formation of these patterns, as well as the granulometric distribution, the permeability and the speed of deposit of the different types of grains that make up the beach. There are several theories that have tried to explain the formation of such patterns (Woodford, 1935, Stauffer et al., 1976, Allen, 1982, Ikeda, 1983, and Devauchelle, 2010), however, none of them has been conclusive. In spite of the above, the study carried out by Devauchelle et al. (2010), concludes that the formulation of a complete theory to describe the formation of such patterns should include the coupling between sediment flow and transport, which is in line with the proposed theory in this initiative.
Currently, the samples are being analyzed to obtain the distribution of grain sizes as well as the speed of the fall of the sand fractions to establish the starting point and define the main axes of the present investigation. Samples of sand were collected at Tres Vidas Beach in Punta Diamante, Acapulco, specifically at the coordinates: 16 ° 43 '30' 'north latitude and 99 ° 43' 24 '' west longitude, where Ricardo observed the formation of these patterns. Future work consists in trying to replicate these patterns in controlled conditions in the laboratory.
Acknowledgments: We thank the Laboratory of Coasts and Ports of the Institute of Engineering (IINGEN) of the UNAM for allowing us to use the equipment to carry out the granulometric analysis. Specifically, Dr. Edgar Mendoza Baldwin, Masters in Science. Cesia Cruz and Engineer David Rosales. The results published on this site are not the responsibility of IINGEN-UNAM and are part of an ongoing investigation carried out independently.
References:
Woodford, A. O. (1935), Rhomboid ripple mark, Am. J. Sci., 29 (174), 518-525.
Stauffer, M. R., A. Hajnal, and D. J. Gendzwill (1976), Rhomboidal lattice
structure: A common feature on sandy beaches, Can. J. Earth Sci., 13 (12), 1667-1677.
Allen, J. R. L. (1982), Developments in Sedimentology, vol. 30B, Sedimentary
Structures-Their Character and Physical Basis, vol. 1, Elsevier, Amsterdam.
Ikeda, H. (1983), Experiments on bedload transport, bed forms, and sedimentary structures using fine gravel in the 4-meter-wide flume, Pap. 2, pp. 1-78, Environ. Res. Cent., Ibaraki, Japan.
Figures:
A. Desiccator of sand samples
B. Sand sample inside the desiccator.
C. Camsizer (particle size and shape analyzer) to obtain the granulometric distribution
D. Sample entered into the camsizer (particle size and shape analyzer)
E. Photographs of the grain size of the sample obtained with the Camsizer (particle size and shape analyzer)
F. Testing the velocity of the fall/drop
