Barrier island evolution, middle Atlantic shelf, U.S.A. Part I: Shoreface dynamics

Shoreface morphodynamics on wave-dominated coasts

Soumises a de forts courants de maree et a de rudes conditions de houle, les passes du Bassin d'Arcachon presentent une morphologie particulierement active. Au cours des 300 dernieres annees, l'excursion de l'extremite de la Fleche du Cap Ferret a atteint 8 km tandis qu'alternativement une ou deux passes assuraient la circulation entre l'interieur du bassin et l'ocean. Un modele morphodynamique bidimensionnel horizontal a ete developpe afin de simuler l'evolution du systeme sous l'action de la maree seule ou de la maree et de la houle combinees. La modelisation a l'echelle de plusieurs decennies requiert la determination de conditions de houle et de maree annuelles moyennes, representatives au regard du transport sedimentaire. Les resultats a moyen terme fournissent par consequent des tendances generales d'evolution. Le modele permet dans ces conditions de reproduire, a partir d'une topographie initiale de l'embouchure fictive de profondeur constante, la formation d'une passe et d'un systeme de bancs comparables aux configurations observees par le passe. Les evolutions morphologiques simulees a partir de la situation de 1993 sont moins probantes, par suite des hypotheses limitantes imposees lors du developpement du modele, et par l'absence de representation des tempetes principales responsables du remaniement des passes.

Modélisation morphodynamique d'une embouchure tidale : Application aux Passes d'entrée du Bassin d'Arcachon

Penetration depth of the dynamic response of seabed induced by internal solitary waves

Ripple Migration and Sand Transport Under Quasi-Orthogonal Combined Flows on the Scotian Shelf

A comparison is made between the measured infilling of two test pits off the coastline of San Francisco and predictions using a coastal bedload transport model. The model, based on the work of Madsen and Grant (1967), relates the bedload transport to the bottom shear stress through an empirical relationship based on laboratory experiments. The bottom shear stress is estimated from the bottom currents created by waves and low frequency currents. The model applies beyond the breaker zone in contrast to littoral transport. The test pits, dredged as part of the Southwest Ocean Outfall Project for San Francisco, were located 1.6 km (1 mi) and 3.2 km (2 mi) offshore in 13' m (42 ft) and 16 m (53 ft) of water. The depth of the pits relative to the natural seabed was about 8.4 m (25 ft). The comparison was conducted for a period up to 2 months in the fall of 1978. The paper discussed the quality and scope of available data required as input to the model and shows how regional wave data were trans formed to augment local measurements. Uncertainties in model results stemming from limitations in the input data are presented. With suitable adjustment of the scale of the gravitational term in the expression for the Shields parameter, overall agreement between computed and measured bedload was accomplished within the limits of accuracy of the bathymetric surveys. A sensitivity analysis of selected input conditions and coefficients was also conducted.

https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/download/3698/3381

Ralph H. Cross

Papers

Measured and Computed Coastal Ocean Bedload Transport

Attenuation of Wave-Induced Pore Pressures in Sand