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The interpretation of seabed dynamics on the Netherlands Continental Shelf

Huizenga, Bregt (2008) The interpretation of seabed dynamics on the Netherlands Continental Shelf.

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Abstract:To ensure the safety of navigating vessels on the Netherlands Continental Shelf (NCS), the Hydrographic Service surveys the Shelf with Multi Beam Echo sounders. The deployment of the survey vessels is done according to a survey policy, which contains resurvey frequencies for each specific area. The survey policy is based on four factors: Minimum depth, draught, shipping intensity and seabed dynamics. Based on the survey policy, yearly survey instructions are issued. These instructions are resulting from a comparison of the age of the contents of the source databases and the maximum age allowed by the survey policy. The current problem is now the result of reliability problems of the survey vessels and the relatively high frequencies of the survey policy. When compared to neighboring countries, these frequencies are rather ambitious, and the question is now if it is possible to reduce these frequencies with the aim to optimize the survey policy. In this study, we focus on optimization of the survey policy by means of the interpretation of seabed dynamics. In the southern NCS, several bed forms are present, which have a strong influence on the navigation safety in the shallow sections. Over the last years, a project has been initiated that analyses selected areas in the southern NCS with a statistical method called deformation analysis. This method approximates the seabed with a spatial representation, which is then analysed with a temporal testing procedure to discuss the dynamic character. However, to include the results of this statistical analysis in the reconsideration of the resurvey frequencies of the survey policy, a proper interpretation of the detected dynamics is mandatory. In this study we introduce an approach to zoom in on the most critical areas (areas with the highest risk), based on the factors minimum depth, draught, shipping intensity and influence of human interventions. This last factor is included due to the increased spatial use of the NCS, and recent area planning. We call this selection of the critical areas, the initial prioritization. To quantify the factors for this prioritization, interviews have been executed at the Hydrographic Service. Furthermore, we use a background chapter on the technologies and methods of surveying to become more familiar with the different error sources.
Item Type:Essay (Master)
Hydrographic Service
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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