Characteristic of the dried-up zone formed as a result of the breach of the Kahovka dam

Abstract

The explosion at the Kahovka dam led to formation of new dried-up areas at the bottom of the Kahovka Reservoir, which have specific relief and mechanical composition of soil. Vegetation that has been forming in those dried-up areas for over one year now is already undergoing the first stages of succession and is characterized by high spatial non-uniformity. The study consisted of three main stages: analysis of dynamics of outflow from the reservoir and development of a scheme of hydrographic network at the site of the reservoir’s bed, analysis of soil cover, and analysis of formation of vegetative cover. We analyzed the possibility of combined use of the data of ground monitoring and remote sensing of the course and consequences of the drying. According to the reports of the Ukrainian Hydro-Meteorological Center of the State Service of Ukraine, a chronology of the emptying of the Kahovka Reservoir was created. The hydrological regime of the newly formed territory was identified using a series of satellite images. The dataset was compiled from Level-2 images from Landsat 8 and 9. Sentinel 2 was used as an additional resource. The images were processed using the Sentinel Application Platform (SNAP). We found the effect which the debris of the Kahovka dam has had on the flood level in the area. We observed recovery of the streambed network of the Dnipro River to its state before construction of the Kahovka dam. The hydraulics of the formed floodplains is complex. There are streams with signs of yet uncompleted meandering and many arms. Clustering of spectral characteristics and interpretation of the normalized NDCI and NDWI indices revealed that the spatial non-homogenous structure of the soil cover of dried-up bed of the reservoir is formed by four types of soil: eutric relictigleyic fluvisols, eutric gleyic fluvisols, eutric fluvic gleysols, eutric fluvic subaquatic gleysols. The soils are characterized by diverse granulometric composition (sand, sandy loam, loam, and clay) and various degrees of soil moisture. In the reservoir’s bed, the commonest soils were found to be eutric gleyic fluvisols. We determined the effect of granulometric composition and soil moisture content on the intensity of overgrowth of the reservoir’s bed. We analyzed the general dynamics of the overgrowth of the reservoir’s bed.