STRUCTURE INDUCED LANDFORM CHANGE ALONG THE NORTHERN YUCATAN COAST

Coastal erosion is occurring on a global scale, and while it is partially a natural phenomenon in concordance with sea-level rise, human intensification along the coast can lead to increased erosion rates. Groins are classic shoreline protection structures, with a history extending back centuries. Although groins are successful at impounding sediment updrift, improper design can lead to dramatic erosion downdrift and support the creation of hazardous rip currents. Due to these adverse effects many locations around the world have banned their use; however, along the Yucatán coast their construction remains a common practice. The objectives of this study were 1) to investigate the impacts of an impermeable groin upon beach sediments and beach morphology, and 2) conduct a survey of groins in the Chelem area to understand how the field study results compare to other groin structures in the region. Methods included 1) constructing a temporary impermeable groin in Sisal, and over a 48-hour period intensely monitoring sediment dynamics and morphologic response to the structure presence via topo-bathymetric surveys over 16 predetermined survey lines, and 2) mapping and developing a typology of groins at Chelem. Results showed that 1) the temporary impermeable groin at Sisal, erected during a sea-breeze event, accounted for 63 m³ of sediment accretion in 24 hours, 2) beach recovery occurred rapidly after groin removal, which illustrated the resilience of this natural system, and 3) groins at Chelem, classed into various types, largely had lost their effectiveness. Future coastal management in Yucatán needs to consider both the positive and negative impacts of groin construction.