Coast Protection Against the Action of Waves and Currents

Abstract

According to the information available in the USSR,
 now in the world there are more than 13000 reservoirs with storage capacity over 1 million m? in service and under construction. The largest ones are illustrated in Table 1. In some countries these storage reservoirs constitute rather a great per cent relative to all the reservoirs of the given country. (Table 2). Lately, such reservoirs have substantially grown in number in many countries of the world, especially in the USSR and USA, what is seen from the chart (Fig.1). In this connection, one can conclude on the great area of some reservoirs (reaching sometimes thousands of square kilometers), on their importance in the balance of the controlled runoff, making up in some countries over 95 per cent and on the intensive increase of their storage capacity beginning from the fifties of the present century. The above said is one of the reasons of greater interest in the action of waves and currents of the shore line showing up most intensively on the largest storage reservoirs. The length of the shore line of the USSR reservoirs is over 40000 km. The length of the erosion shores of storage reservoirs at the hydroelectric projects on the Volga and Dnieper River make up more than 30 per cent of the total shoreline of these reservoirs, while that of the reservoirs on the Kama River - 35 per cent. Most intensively the erosion is going on in the first decades of the operation of the reservoirs. The action of waves on the shore results in formation of the underwater slope with a gradient at which the wave energy is dissipated on the shoal, and the shore erosion slows gradually down until it ceases completely. However, it is rather difficult now to determine the period of the shore formation attenuation process in view of the fact that the problem of distribution of wave energy between all the phenomena taking place here is not properly studied yet and it is hot also clear what width and gradient of the shoal can fully baffle the wave energy and how much time it will take for such a shoal to get formed. The observation carried out on the natural water bodies well prove it.