HYDRO 2016 Paper 10A2

Provide end users with the most accurate nautical depth measurement by using the combination of echo sounders and density measurement equipment

Pieter J. de Boer, Coen J. Werner


Harbours and their access channels need to be dredged to the nautical depth to ensure safe vessel passage. When fluid mud is present, a critical density value is determined to establish this depth, which is area specific. Another consideration for establishing the level of safe vessel passage is yield stress. The yield stress indicates the level in the fluid where solidification of the mud occurs. Traditional survey techniques are not capable of detecting multiple density levels or yield stress. To optimise dredging operations and continuous harbour management one could benefit of using an ultra-high resolution sub-bottom profiler in combination with in situ density and yield stress measurements. The geophysical software package SILAS will link both type of measurements and can in real-time determine density levels which spatially cover the entire harbour or access channel, therefore excluding interpolation in the process. The SILAS software enables all users to manage the nautical depth, while batch processing and data cross-referencing acquired using different sources can improve the overall data quality as well as provide the user with a more detailed understanding of sub-bottom features, such as cables and pipelines. Recent studies show that the SILAS system can detect various types of sub-bottom objects not only limited to cables and pipelines, but also individual boulders. These objects can be detected with a success rate of 75% and over on objects and cables with a diameter of 25 cm or higher.

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