Variability in Onshore Sediment Transport on a Natural Beach during a Central American Cold Surge Event

Abstract

Briggs, T.R.; Figlus, J.; Torres-Freyermuth, A.; Puleo, J.A.; Warren, W., and Alrushaid, T., 2020. Variability in onshore sediment transport on a natural beach during a Central American cold surge event. Journal of Coastal Research, 36(3), 487–497. Coconut Creek (Florida), ISSN 0749-0208.Beaches facing the Gulf of Mexico along the northern part of the Yucatan Peninsula experience frequent Central American cold surge events, or northerly storms locally called “Nortes,” which interrupt the usual daily patterns of sea- and land-breeze–dominated nearshore dynamics. These perturbations of prevailing hydrodynamic forcing conditions also affect sediment distribution and transport parameters in the surf and swash zone, which are critical elements in understanding and modeling complex morphodynamic processes during storm events. However, detailed measurements of sediment characteristics throughout the water column during a storm event are scarce. This study presents field measurements of bottom and suspended sediment transported in the onshore direction during a 24-hour storm event impacting the Yucatan Peninsula. Sediment load data within the water column collected in 3 hour intervals via vertical arrays of streamer traps, deployed at two cross-shore locations in the inner surf zone, are compared with sediment data from collocated bottom grab samples. Time series of grain size distributions, sediment statistics, and respective vertical variations throughout the water column are related to measured bed-level changes to verify applicability of simple erosion and accretion predictors. Results indicate that bottom sediment and sediment distributions throughout the water column deviate substantially due to storms, highlighting the complexity and difficulty of assessing sediment transport and morphodynamic processes with a single-parameter sediment characteristic. Calculated total onshore transport rates during the Norte were on average one order of magnitude higher than during nonstorm conditions.