Bypassing at a headland-controlled meso-scale tidal inlet

Abstract

In this paper, a conceptual model is presented addressing the morphological evolution of a headland-controlled inlet at Babitonga Bay, Southern Brazil. Multiple historic bathymetric datasets were compiled spanning a period of 160 years (1862–2021). A test of various interpolation methods identified the Empirical Bayesian Kriging interpolation method as the most suitable to reconstruct the morphological features presented in nautical charts. The morphological evidences indicates that the basin-channel orientation, i.e., outflow configuration onto the ebb tidal delta and the Longshore Transport rate affect the headland-inlet bypassing mechanism. The first stage (1862–1941) revealed a volume gain along the Ebb tidal delta downdrift lobe. While the northwest channel and updrift coast were erosive, several deposits formed in the channel updrift side. This phase relies on sediment remobilization along the updrift coast and wave deposition dominance at the inlet's entrance and along the updrift channel side. The wave-dominance increase the nearshore headland bypassing and erode the downdrift channel bank, supplying the associated lobe. The second stage (1941–1972) was remarkable by accretion across the ETD. At the channel landward sector, cross-sectional asymmetry suggests the formation of a straighter ebb channel. This indicate the channel became dominated by tidal currents. On the other hand, wave-induced deposition dominated at the downdrift lobe, inducing a longshore transport reversal and an ETD sediment-trapping phase. During the third phase (1972–1995) the updrift channel sector was erosive, suggesting a longshore transport rate decreasing at the inlet's entrance and a ETD outer shoal bypassing. The fourth phase (1995–2021) was related to a higher LST rate, regarding the updrift coast was erosive and the landward channel compartment imputed sediment again.