Analysis of the Bottom Topography of the Reservoir Due to Sediment Trapping (According to the Krasnodar Reservoir, Russia)

Abstract

Morphometric descriptions of reservoirs are usually limited to the type, shape, altitude position, bed size and volume of water in them. The article presents the results of the analysis of the bottom topography of the Krasnodar reservoir and the transformations of this for 2005-2021. The analysis was carried out based on the materials of bathymetric surveys for the usable volume of the reservoir on an area of 224 km2 with the creation of digital elevation models. The topography of the reservoir bottom is represented by flat sections of flooded accumulative plain with prevailing slopes of about 0.2–0.4°, dissected by riverbeds of lower-order tributaries. The transformation of the topography is caused by gradual silting. The total volume of sediments for this area in 2005-2021 amounted to 127 million m3 with an average siltation layer of 0.4 m. To describe the morphological properties of the bottom topography, we used geomorphometry techniques with the calculation of the BPI index (Bathymetric Position Index) and the classification of mesoscale topography forms based on it. For the riverbed, there are topography forms related to three types of surfaces: flat (Lower Bank Shelves), concave (Depressions, Deep Depressions) and convex (Reef Crests, Back Reefs, Mid-Slope Ridges). The constructed maps reflect the differentiated morphology of the bed surface, the evolution of topography forms and the change in roughness under conditions of continuous transformation of the basin and allow judging the prevailing morphogenetic processes. Morphologically, the coastal zone and the shallow part of the riverbed are the most difficult to construct. Here, along with long-shore reef crests of different genesis, deep depressions and simple depressions in the form of underwater channels on the deltas of extension can form on the accumulative shoal.