Characterization of Intertidal Bar Morphodynamics Using a Bi-Annual LiDAR Dataset

Abstract

Intertidal bars are common features on meso-and macro-tidal sandy beaches with low to moderate wave energy environments. Understanding their morphodynamics is, hence, crucial for enhancing our knowledge on beach processes which is beneficial for coastal management. However, most studies have been limited by assessing bar systems two-dimensionally and typically over the short-term. Morphology and dynamics of an intertidal bar system in a macro-tidal environment have been investigated using bi-annual LiDAR topographic surveys over a period of seven years and along 3.2 km at Groenendijk beach (Belgium). The detected bars demonstrate that a morphology of an intertidal bar is permanently on the beach. However, these individual features are dynamic and highly mobile over the course of half a year. The mean height and width of the bars were 1.1 and 82 m, respectively. The highest, steepest, and asymmetric features were found on the upper beach, while they were least developed in the lower intertidal zone. The bars were evenly distributed over the entire intertidal beach, but the largest concentration observed around the mean sea level indicated the occurrence at preferential locations. The most significant net change across the beach occurs between the mean sea level and mean-high-water neap which corroborates with the profile mobility pattern. The seasonal variability of the bar morphology is moderately related to the seasonally driven changes in storm and wave regime forcings. However, a distinct relationship may be inhibited by the complex combination of forcing-, relaxation time- and feedback-dominated response. This work conducted from bi-annual LiDAR surveys has provided an unprecedented insight into the complex spatial organization of intertidal bars as well as their variability in time from seasonal to annual scale.

Spatial-temporal variability: characterisation of a beach system using high resolution radar data

“…Rather, smaller, and more localized patterns of erosion and accretion along the cross-shore can provide an evidence-base for how the intertidal zone responds to different environmental conditions. The morphological variability of intertidal landforms, such as bars, are spatially heterogenous, particularly between the lower and upper sections of the beach (Montreuil et al, 2020). This is reflected in the findings within this paper, displaying a greater variability of morphological change seaward, with lower variability in the upper intertidal zone.…”

Assessing Storm Response of Multiple Intertidal Bars Using an Open-Source Automatic Processing Toolbox

“…Ref. [5] further observed significant changes in bar dimension and shape with a clear seasonal variability between spring and autumn associated with energetic and calm hydrodynamic conditions, respectively. A continuous and full recovery of the upper-beach was observed after 9 months when sand was deposited there and near the dunetoe.…”

“…The shoreface also displays a subtidal bar. Bar dimensions are typically around 1.1 m high and 82 m wide [5]. Cross-shore drainage channels segment the bar-trough system.…”

“…They are commonly present in low to moderate energy coastal environments (i.e., exposed to fetch-limited waves) characterized by a surplus of sand and tidal ranges larger than about 3 m [1]. The multiple intertidal bar systems are well-developed around semi-enclosed epicontinental seas such as the eastern English Channel, the Irish Sea and the North Sea (e.g., [2][3][4][5]). Bars are permanent or to semi-permanent features, <1 m high and attaining covering up to lengths of up to several kilometres.…”

Conceptualizing Aeolian Sediment Transport in a Cellular Automata Model to Simulate the Bio-Geomorphological Evolution of Beach–Dune Systems

“…To illustrate this agreement, we compared our model Furthermore, the size of the non-vegetated aeolian bedforms on the beach surface for the landward propagation mode (Figure 7a) did not correspond with the bedforms observed in real beach environments. Non-vegetated bedforms on the beach can range in height from small ripples of a few centimeters [23] to larger sand patches with heights of tens of centimeters [58][59][60][61]. For the default jumping length, which produced the landward propagation mode in the wide and prograding beach scenario, bedforms on the beach surface were predicted to have heights in the order of a meter (Figure 7a), much greater than the observed dimensions in the field.…”