Elevation-Dependent Multiscale Analysis of a Complex Intertidal Zone

Horne, P.; Suteanu, C.; van Proosdij, D., and Baker, G., 2013. Elevation-dependent multiscale analysis of a complex intertidal zone. Coastal geomorphology is the result of many complex interacting processes operating over a range of scales in space, and multiscale analysis on relevant scale intervals can help link form with process. Numerous studies focus on lines resulting from the intersection of a plane at a certain elevation with the three-dimensional landscape. However, in most cases, the reason for the choice of the actual elevation is not mentioned, nor at times is the value of the selected elevation even specified. Such an approach relies on the assumption that one studies an isotropic, self-affine pattern for which the irregularity is independent from elevation. The present study questions this assumption by applying fractal analysis not to one, but rather to a series of different elevations relating to tidal stages. The research takes place in a macrotidal estuary, in the Upper Bay of Fundy, Canada, where diurnal tides exceed 14 m. The topography of Avon Estuary is influenced by complex interacting factors, including hydrodynamic and sedimentary processes, vegetation, and ice formations, as well as by anthropogenic structures. The area–perimeter analysis method was applied to 0.5-m contour intervals on a digital elevation model derived from a light detection and ranging survey conducted at low tide. The results show a pronounced and coherent dependence of the fractal dimension on elevation. Fractal dimensions between 1.2 and 1.17 are generally associated with sand sediment transport and bedform development at elevation ranges from −5 to −1 m Canadian Geodetic vertical datum of 1928. Between D values 1.7 and 1.12 at elevations from −0.5 to 2.5 m CGVD28, vertical accretion processes dominate with bank edge erosion. D values continue to increase above elevations greater than 3 m as vegetation becomes established and stabilizes the intricate tidal creek networks. We show that this approach supports a better understanding of the interacting processes that dominate the area on different ranges of scale.