Determining route survey periodicity for mine warfare investigation of bedforms, waves, tides and currents

Abstract

To retain maritime security, an up-to-date database of mine countermeasures route surveys is essential. In 2005, the United Kingdom Hydrographic Office (UKHO) developed a GIS weighted suitability model to determine survey periodicity; allowing optimization of survey resources, increasing time and cost efficiency. The U.S. currently has no such model. Bedforms are an integral part of the survey periodicity problem. Sediment grain size, tides, currents, and wind-generated waves are influential in bedform formation. In this thesis, San Francisco Bay was chosen as a case study. To investigate if sediment properties change over time, localized grab samples for a three-year period were analyzed. The analysis showed little variability in sediment characteristics at a given location. A weighted suitability model based on the UKHO model was constructed. Three layers were developed including sediment grain size, interpolated from 174 grab samples, tidal and current data from over 50 current stations and ripple height inferred from wind generated wave height. A weighting for each layer was determined. Regions indicating the presence of bedforms were assigned a low survey periodicity, as bedforms reduced, survey periodicity was increased. High-resolution multi-beam survey data was used as a comparison and validation, this showed extremely good correlation with the model.