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The relief of the offshore sea bottom at Karwia-Chałupy, Polish Baltic coast

100%

Gajewski L. , Gajewski Ł. , Rudowski S. , Stachowiak A.

tom Vol. 11

91-94

Morphology of sea bottom of the Władysławowo area, from Karwia to Chałupy, has been studied based on the detailed digital bathymetric map prepared in a scale of 1:25 000 with isobaths every 0.25 m. A significant differentiation of the bottom relief has been observed, with the level changes up to 1-3 metres, mostly connected with the occurrence of specific systems of ridges and runnels. They are probably partly relict forms (fluvial and/or coastal?), changed to certain degree during the rapid stage of the Litorina transgression, and in partly forms created by the recent waves. Several types of the sea bottom surface, differing in pattern of morphological forms, have been recognised within inshore, near shore, and open sea (above 16 m depths) areas. The full knowledge of the origin and development of these relief forms requires further specialised research, currently carried out. Nonetheless, the already obtained picture of the sea bottom relief indicates an intensified abrasion of the offshore sea bottom, and an intensive, irreversible sweeping out of the sediments from the shore to the open sea, most probably by rip currents, at a distance up to several kilometres from the shore. It is in accordance with the results of a former large-scale (1:500) study of the sea bottom at the test field at Chłapowo, performed with the use of an integrated system of non-invasive and direct methods.

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

100%

Rudowski S. , Gajewski L. , Jezionek E.

tom Vol. 29, No. 3

85-92

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.