The Geomorphological Structure and Processes in Urban Areas of Abkhazia

Based on the results of expeditionary geomorphological studies carried out in 2021–2022 with the involvement of published materials, a large-scale (1 : 25 000 to 1 : 100 000) characterization of the relief of the urban areas of the Republic of Abkhazia (Gagra, Pitsunda, Gudauta, Noviy Afon, and Sukhum) was compiled for the first time. In addition, previously unparalleled general geomorphological maps were compiled, the legends of which were prepared following the morphogenetic principle. According to the morphostructural position and geomorphological structure, the cities are divided into three groups: (1) completely in the area of distribution of the coastal-marine relief (Pitsunda and Gudauta), (2) located mainly within the sea terraces and erosion-denudation hills (Sukhum and Gagra), and (3) completely located in the low mountains with a predominance of strongly dissected structural-denudation, fluvial and slope relief (Noviy Afon). A field survey revealed about 300 areas of manifestation of unfavorable and dangerous geomorphological processes in urban areas, of which 44% are in Sukhum, 26% in Gudauta, 11% in Gagra, 10% in Pitsunda, and 9% in Noviy Afon. The leading places in the spectrum of geomorphological hazards belong to suffusion, erosion, and biogenic processes. The composition of other processes in the spectrum is determined by the geomorphological position of cities under consideration. The widest range, including, in addition to the processes mentioned above, karst, mudflows and landslide processes (i.e., the most dangerous ones), is typical of urban areas with a complex relief structure, an abundance of steep slopes and located within a narrow zone, separating the spurs of the Main Caucasian Range from the sea (Gagra and Noviy Afon). A qualitative assessment of the risk of destruction of street infrastructure (roadbed, communications, etc.) by dangerous geomorphological processes has been carried out and a high degree of its dependence on the geomorphological position of a particular section of the city has been established. In particular, based on the distribution patterns of recorded manifestations of unfavorable and dangerous geomorphological processes, it has been established that the most favorable conditions for the construction and operation of urban infrastructure and buildings are created generally within the leveled surfaces of the Late Pleistocene marine terraces, as well as at the upper levels of floodplain terraces in the large river valleys. Other levels of relief reflect certain disadvantages that make the development of the territory under consideration difficult. Thus, construction on the surface of the Holocene marine terrace is possible only if the foundations are waterproofed and soil is dumped in the lower areas. The development of high sea terraces and erosional-denudation and structural-denudation relief is difficult due to the high density of erosional dissection.