Méthode d’analyse factorielle appliquée au suivi bathymétrique de l’embouchure de l’Adour

Abstract

Résumé:Une base de données de 36 relevés bathymétriques réalisés entre décembre 2001 et septembre 2003 dans l'embouchure de l'Adour a été étudiée par la technique d'analyse factorielle. Couramment utilisée pour caractériser l'évolution morphodynamique des plages sableuses, cette méthode d'analyse statistique reste rarement employée dans les études de données bathymétriques d'estuaires. Cette étude montre l'intérêt de l'analyse factorielle pour caractériser la dynamique sédimentaire d'une embouchure soumise à l'impact anthropique. L'analyse factorielle permet de réaliser une forte compression des données et simplifie l'analyse du comportement hydrosédimentaire de l'embouchure. Ainsi, Les premiers résultats obtenus ont permis de mettre en évidence des comportements significatifs et laissent entrevoir le développement d'un modèle morphodynamique empirique moyen terme. Abstract:A bathymetric data set of the Adour river mouth, composed from 36 surveys for dates between December 2001 and September 2003, were studied by using Empirical Orthogonal Function (EOF) analysis. EOF has become an established technique for investigating seabed level fluctuations but the use of EOF is currently scarce for estuary studies. This study shows the efficiency of this statistical method to characterize the behavior of a river mouth subjected to dredging activities. EOF consists in an important data compression which simplify the analysis of the river mouth. Hence, The first results underscored significant behavior and would allow to develop an empirical medium-term morphodynamic model.

Assessing the Spatial and Temporal Volumes of Siltation with a Historical Approach: Application in Nador’s Harbor (Morocco)

“…Because the inner part (muddy sand and mud) is characterized by the presence of continental-origin vases, it is influenced by continental input Every numerical modeling method has a margin of error, and the results of this study were limited to a marine hydrodynamics map that controls the deposition of sediments at the bottom of the harbor. The maximum and minimum volumes calculated for each basin were theoretical results obtained by using the trapezoidal rule (Maron and Rihouey 2003;Marron et al 2004); they provided information on the marine dynamics that controls the siltation at the harbor bottom.…”

“…Nador's Harbor was considered as a case study, and Surfer 12 was used to model the surface in three dimensions using the krigeage method (Cressie 1990;Cressie 1991). The modeled grids were traced to obtain the crosssections of the bathymetric data, and the sediment volume was calculated for each basin in Nador's Harbor based on the trapezoidal rule (Maron and Rihouey 2003;Marron et al 2004). …”

“…The result is called a grid. A grid is essential for tracing iso-contours, calculating volumes or surfaces, and generating cross-sections in different directions (Gorman et al 1998;Marron and Rihouey 2003;Marron et al 2004).…”

“…The entire grid was subtracted by using the slice command (Golden software Inc. 1999), and the sediment volume was calculated for each surface by using the trapezoidal rule (Maron and Rihouey 2003;Marron et al 2004). Table 1 summarizes the difference between the maximum and minimum sediment volume, average volume of each basin, and area of the seven basins and initial depth corresponding to the seven basins.…”

“…The sediment volumes were evaluated by using the trapezoidal rule (Maron and Rihouey 2003;Marron et al 2004). In this case, the lower surface corresponded to the initial depth of the harbor basins.…”