Transport of sediments resuspended by ferries

Abstract

In this study we propose a scheme of sediments transport in Tallinn Bay. Our previous works used optical methods to estimate that fast ferries bring into motion of the order of nearly 10,000 kg of sediments per running meter of coastline per year. But the question is still open, where the sediments will be transported and which part of them will be carried out of the coastal zone. We used an Aanderaa sonde RDCP 600 to measure the wakespsila velocity and direction near the most endangered coast. The results were somewhat unexpected - the near bottom velocity (~0.1 m/s) was typical for the Tallinn Bay, but for all the measurements the direction was not along the shore but 45deg from the shore line. That means the sediments brought into motion by the fast ferries will quickly and irreversibly be transported away from the coast to the deeper (20-50 m) sea areas. Wave parameters were recorded and analyzed during the experiment also. Ferry wakes were categorized by the height as well by the period.