Studies ordered by the Ministry of the Environment (MoE) confirm the supposed damaging effect of intensive shipping traffic on the coastal areas and aquatic life of Tallinn Bay, but also on small crafts on the entire Bay. The main aim of the study coordinated by the Estonian Marine Institute is to ascertain the possible role of ship backwash in coastal erosion, and, if necessary, to provide recommendations for coastal protection. Upon completion of the study, the MoE will forward the findings to the Ministry of Transport and Communications, requesting the latter to consider possibilities to establish speed limits for the traffic of high-speed crafts on Tallinn Bay, or to carry out additional expert assessments. According to Rein Raudsepp, Director of Environmental Management and Technology Department of MoE, the danger of damage by ship backwash is bigger on the southwester coast of Aegna island, in the harbour area of Naissaar island, and on Viimsi peninsula near Pringi, as these areas are affected by more intensive coastal processes. One of the aims of the studies is to assess the role of ship backwash in coastal damage and erosion. The highest of ship backwash waves are generated by high-speed crafts. At the distance of two to three kilometres from the shipway, their single waves can be as high as 1.8 metres and at the distance of eight kilometres – 0.7 metres. In a calm weather, the backwash waves of high-speed crafts can strongly lift bottom sediments at the depth of five or more metres. The measuring also revealed that waves generated by hydrofoils and ordinary ferryboats are considerably weaker and essentially indistinguishable from natural background. The structure of waves generated by high speed crafts is similar to that of solitons – solitary waves that have a specific structure and can spread for many kilometres with a practically unchanged shape and height, and whose impact on the coastal slope and bottom sediments is much stronger than that of equally high natural waves. The study was financed by the Centre for Environmental Investments. The MoE ordered the study from the Estonian Marine Institute, winner of the relevant public procurement procedure, in summer 2001, since an increasing number of protests was filed on the damaging impact of high speed crafts' backwash. Fishermen, local inhabitants and border guards have repeatedly pointed out that the high waves generated by ships of a certain type pose a danger for small floating vessels and fishing nets. The second phase of the project, which finishes in September 2002, will focus on assessing the role of natural waves and waves generated by high speed crafts in the dynamics of coastal processes, including underwater transport of sediments. Additional information: Rein Raudsepp, Director of Environmental Management and Technology Department, tel. + 372 627 3051, +372 50 66610. |
