Nearshore Waves and Littoral Drift Along a Micro-Tidal Wave-Dominated Coast Having Comparable Wind-Sea and Swell Energy

Abstract

The nearshore wave characteristics and variations in littoral drift (longshore sediment transport; LST) are estimated based on different approaches for four years along the Vengurla coast, with comparable wind-sea and swell energy assessed. The waverider buoy-measured data at 15 m water depth is utilized as the input wave parameters along with the reanalysis model data, and the numerical wave model Delft-3D is used for estimating the nearshore wave parameters. The relative contribution of wind-seas and swells on LST rates are specifically examined. The clear prevalence of west-southwest waves implies the prevalence of south to north longshore sediment transport with net transport varying from 0.19–0.37 × 105 m3/yr. LST is strongly dependent on the breaker angle and a small change in the wave direction substantially alters the LST, and hence reanalysis/model data with coarse resolutions produce large errors (~38%) in the LST estimate. The annual gross LST rate based on integral wave parameters is only 58% considering the wind-seas and swells separately, since the wind-sea energy is comparable to swell energy, and the direction of these two systems differs significantly.

Implication of Shoreline and Nearshore Morphological Changes on Sediment Budget of Wave-Dominated Chennai Beach, India

“…Understanding the physical processes in the nearshore region is very much essential to derive the causes of erosion/ accretion. The morphological changes in sandy beaches are mainly due to the wave action and current pattern (Jesbin et al 2020).…”

“…Shorelines are highly dynamic due to complex hydrodynamic processes (wave, tide, and sea level rise), meteorological-geophysical events (cyclones, wind, rainfall, earthquake, tsunami), natural processes (littoral drift, sediment and water discharge), and anthropogenic activities (coastal protection structures and urbanization) (Mishra et al 2019;Markose et al 2016). Beach is the most dynamic zone due to the nearshore processes like reflection, refraction, bottom friction, shoaling and breaking of waves (Jesbin et al 2020). Sandy beaches are the main focus of the littoral morpho-dynamics investigation (Osborne 2005).…”

“…Samaras and Koutitas (2014) evaluated the efficiency of various empirical equations and derived that the LST rate estimated using Kamphuis (1991) formulae correlate with the laboratory measurements. Bulk transport formulae provide LSTR estimation of a profile with few input parameters (Jesbin et al 2020). The Kamphuis (1991Kamphuis ( , 2002 formula includes the parameter like wave height/ direction/ period, beach orientation/ slope, and median sediment grain size which are the factors influencing the estimation along the Indian coast (Shanas and Sanil 2014;.…”