Tides and Waves

A Bayesian failure model based on isotropic deterioration

Coastal dynamics and shoreface relief in ice-free seas are a function of hydrodynamic interactions between the sea and bottom sediments. In the Arctic, additional, cryogenic factors such as permafrost and the action of sea ice influence coastal processes. The goal of our paper is to assess this influence, mainly on the profile shape. Mathematical analyses of the shape of 63 shoreface profiles from the Laptev, Beaufort, and Chukchi Seas were carried out. The shapes of Arctic shoreface profiles and those of ice-free seas are compared. We found that large ice and silt content in perennially frozen sediments composing Arctic coasts favor their erosion. Sea ice plays an important role in sediment transport on the shoreface and correspondingly changes shoreface relief significantly. Some effects of ice intensify coastal erosion considerably, but others play a protective role. The overall influence of cryogenic processes on Arctic coasts composed of loose sediments is seen in that the average rate of co...

https://bioone.org/journals/journal-of-coastal-research/volume-2008/issue-241/05-0573.1/The-Influence-of-Cryogenic-Processes-on-the-Erosional-Arctic-Shoreface/10.2112/05-0573.1.pdf

The Influence of Cryogenic Processes on the Erosional Arctic Shoreface

Extended equilibrium beach profiles

The configuration of equilibrium beach profile in South China

The Submarine Profile (SP) is the sea floor profile normal to the coast line, located between the surf zone and wave base and formed by wave action on the clastic sediment. The Submarine Equilibrium Profile (SEP) is a SP where geometry and sediment movement are in a quasi equilibrium status with offshore nominal waves (the large swell dominating this area). The geometry of the SEP has been identified qualitatively and conceptually as a concave upward smooth curve. The slope of SEP becomes gentler and gentler offshore until it is almost horizontal at the so-called wave base. Some empirical equations have been proposed and are used widely in engineering. This report summarizes previous field observations, lab experiments and theories concerning mechanisms involved in the formation of this geometry. A series of physical equilibrium conditions, including the major mechanical forces involved in particle movement, are used to derive an analytical model. This model expresses the geometry of the SEP in an explicit form where x is a function of y, in relation with the offshore wave period (or wave length). The basic idea has been qualitatively tested in a wave tank experiment. The final equation was then tested and calibrated on a number of submarine profiles plotted from three marine basins around the U.S. using a non-linear regression algorithm. The profiles located on the U.S. coasts along the Gulf of Mexico and on southeast U.S. Atlantic coasts were selected following geological and visual criteria which previous researches used to characterize the SEP concept. The comparison between the theoretical equation and the selected Gulf of Mexico and Atlantic profiles by a non-linear computer regression process showed a satisfactory match with high correlation coefficients. The Pacific profiles, located in an area with ongoing active tectonic movement are generally not in SEP status and have more features deviating from the conceptual and SEP physical models. The wave periods obtained from the nonlinear regression process for some SEP's on the Gulf of Mexico coast are further compared with the available hindcast offshore wave data published in 1989. The results of these comparisons are generally encouraging, except those comparisons involving SP's on the U.S. Pacific coast.

/pdf/the-submarine-equilibrium-profile-a-physical-model-4qcct3jwo9.pdf

Paul Zi-Fang Lee

Papers

The submarine equilibrium profile: a physical model