Application of the hydroacoustic methods to the detailed determination of the seafloor condition in the area of roadsteads and anchorages

The detailed study of the bottom condition of the Anchorage No. 3 of the Gdynia roadstead is presented. The study applies the integrated system of the modern hydroacoustic methods (mainly a multi-beam echosounder, side-scan sonar and subbottom profiler). Results of the hydroacoustic recordings were interpreted using data from grab and core samples as well as a floor inspection done by ROV system of the underwater TV. The morphology and character of the bottom were recognised thoroughly including effects of the human activity (dredging, trace of anchors, presence of anthropo-genic objects etc.). The digital bathymetric map and the map of surface sediments of the bottom test field were prepared. The bottom condition was determined as the area of the gravitational sedimentation of silty-clayey sediments, which have strongly changed anthropogenicly to the depth of 0.5-1.0 metre below bottom level. The obtained results point to the high efficiency of the applied research method. The conducted manner of recording, together with adequate calibration and equipment adaptation to the local conditions allow applying the methodology to future routine studies of the sea bottom for determination its condition. Also, a valuable cognitive material related to the geological structure of the bottom was collected.