ABSTRACT Carvalho, A.M.; Lima Jr., S.B.; Maia, L.P.; Claudino-Sales, V.; Gastão, F.G.C.; Eduardo, L.M.; Pinheiro, L.S., and Silva, M.V.C., 2021. Understanding polydirectional aeolian cross-strata architecture in a coastal unidirectional wind regime. Journal of Coastal Research, 37(2), 364–379. Coconut Creek (Florida), ISSN 0749-0208. Crescentic dune fields along the NE coast of Brazil were analyzed to justify processes associated with the wide range of cross-strata dip directions in aeolian deposits found in a unidirectional wind regime. Multiple spatial and temporal field-based methodologies were employed, including trenching, ground penetrating radar (GPR), and photogrammetry. Wind dynamics, coastline morphology, bounding surface developing processes, and dune migration patterns were also considered. Analysis revealed a relationship between small- and large-scale morphologies of the crescentic dune field. The interactions of crescentic dune crests, in association with the superposition of multiple superposed dunes, explain the majority of cross strata and dip directions found in dune trenches and GPR sections. This study provides convincing evidence that microscale structures observed within trenches and GPR sections are compatible with the macroscale slipface position observed within the dune field. Small-scale changes in wind direction, caused by the dune crest morphologies themselves, explain much of the supposedly unexpected strata dip directions that arc through from 90° to 180°. The presence of near-surface water tables supports the formation and preservation of aeolian cross-strata sequences.

ABSTRACT Claudino-Sales, V.; Wang, P., and Carvalho, A.M., 2018. Interactions between various headlands, beaches, and dunes along the coast of Ceará State, Northeast Brazil. The equatorial coast of NE Brazil consists of long and wide sandy beaches, segmented by rhythmic headlands, sometimes with seacliffs. Large and extensive mobile transgressive dunefields distribute up to 6 km landward of the coastline. The coastal area of Ceará state, as examined in this study by the means of measurements, field work, and remote sensing, illustrates a characteristic morphology composed of interactive headland, beach, and dune systems. Under persistent unidirectional wind and wave forcing, the morphodynamics of the studied coast is strongly controlled by the headlands because they produce an interruption of the longshore sand transport at their contact, resulting in accretion updrift of the headland and in erosion downdrift of the headland. The headland bypass dunefield activates one major mechanism and dynamics of the system headland-beach-dune because they refeed the beaches in the process of erosion downdrift. Littoral bypass is also an important process, supplying the cell with new sand, together with the erosion that takes place in the zetaform beach. Such a unique system can be strongly affected by anthropogenic activities, which can influence nearly all the factors at all temporal and spatial scales.

Santa Rosa Island, situated along the northwestern Florida coast facing the Gulf of Mexico, is an 85-km-long wave-dominated low-lying barrier island with well-developed incipient and established dunes. In this paper, we examine the regional-scale effect on coastal dunes by a strong category 3 hurricane, Ivan, through comparison of pre- and poststorm airborne LIDAR (light detecting and ranging) surveys. On the basis of pre-Ivan LIDAR survey data, the elevation of the berm and back beach is typically 2.0 m above MSL (mean sea level). Incipient dunes range from 2.5 to 10 m above MSL, or 0.5 to 8.0 m above the surrounding beach. The hummocky dunes that developed over relic washover platforms are typically less than 4.0 m above MSL. The densely vegetated, established dune fields are composed of dunes less than 7.0 m high and intradune wetlands lying at less than 1.0 m above MSL. The entire island was severely affected by Ivan, which made landfall about 45 km to the west in September 2004. The landscape was substantially changed by Ivan. Over 70% of the incipient and hummocky dunes were destroyed, and a large portion of the low-lying wetlands was covered by washover. The degree of storm-induced morphology change depends not only on the intensity and duration of the storm but also on the antecedent morphological characteristics of the barrier island. Comparison of pre- and post-Ivan cross-island LIDAR profiles indicates that at most locations, more sand was eroded from the subaerial portion of the barrier island ( e.g., beach and dune) than was deposited as washover terraces and lobes. This suggests a net sand loss to the offshore region. Evidence of sand moving alongshore related to the oblique orientation of the dunes was also identified. Under inundation regime, the subaerial sediment deficit could be accounted for by subaqueous sedimentation into the back-barrier bay.