THE INFLUENCE OF LARGE HYDROTECHNICAL CONSTRUCTIONS ON GEOMORPHOLOGICAL PROCESSES IN VALLEYS

Abstract

The numerous large storage reservoirs essentially change the landscape of many river valleys. The rising of the erosion basis, caused by the construction of a dam, as well as the transformation of a hydrologic regime of a river under the influence of the storage reservoir, are the reasons for a sequence of interrelated geomorphological processes. From the edge of the affluent, caused by the dam, further up the river there gradually spreads a regressive accumulation, due to which simultaneously with the rising of the valley floor, the levels of water in the river also rise. Within the storage reservoir itself, under the influence of waves, lengthwise currents, seasonal changes of the water-level, and gravitational processes on the slopes, there forms a peculiar relief of the coast, characterized by large areas of recurrent inundation, an abundancy of lagoons — detached bays, and high cliffs of retreating banks in the abrasion areas. Downstream below the dam there develops deep erosion. A terrace forms rapidly here, the relative height of which on the main river diminishes towards the mouth, while on the tributaries, on the contrary, it increases towards their estuaries.