SURFACE MORPHOLOGY AND DYNAMICS COASTLINE OF THE DZHARYLHACH SPIT DISTAL END
Authors: Davydov O. V. , Kotovskyi I. M. , Onoyko Yu. Yu. , Simchenko S. V. 
Published: February 2023

Introduction. Dzharylhach spit is the largest accumulative form within the Black Sea coast. Erosion processes have appeared along the front of the spit, which in certain local areas (“hot spots”) are quite dangerous and can cause the spit’s body breaks. Within Dzharylgach, “hot spots” are located in the proximal and distal parts.
The Dzharylhach distal end is an important recreational facility that hosts tens of thousands of vacationers every year. The breach formation within the distal end will make its recreational use impossible, which in turn will lead to significant negative changes in the economic sector of the southern region of Ukraine. That is why the study of the morphological and morphodynamic conditions of the Dzharylhach distal end is relevant and has a very important economic emphasis.
Research aim is to determine the modern morphological and morphodynamic conditions of the Dzharylgach spit distal part development, based on the materials of field and remote studies. Following research objectives would facilitate the achievement of this aim: a) to define the distal end concept and to describe the morphodynamic diversity of the accumulative forms’ corresponding component; b) to analyze the morphological conditions of the Dzharylhach spit distal end and to determine its constituent parts; c) to determine the quantitative parameters of the coast’s dynamics within the distal end based on the materials of field research, GPS‑fixation of coastal landforms and analysis of satellite images of different ages; d) to compare the results of remote sensing with the materials of the Global monitoring of beaches and determining the morphodynamic trends of the Dzharylhach spit distal end development.
Research object is the Dzharylhach spit distal end. Research subject is the morphological and morphodynamic conditions of the Dzharylhach distal end development.
Research methodology. A comprehensive approach was used to study the morphological and morphodynamic features of the Dzharylhach distal end, which was based on the analysis, comparison, and systematization of field geomorphological leveling materials, GPS‑fixation of the coastal landforms position, analysis of satellite images and Global remote monitoring of beaches. 27 ISSN 2303-9914 Вісник ОНУ. Сер.: Географічні та геологічні науки. 2022. Т. 27, вип. 2(41)
Research results. The distal end of any free coastal accumulative form is its morphological component, which is as far as possible from the place where the form leaned against the bedrock coast. From the outside, the distal end has the appearance of a cape with an adjacent shoal, which protrudes towards the seawater area. In dynamic terms, the distal end is the most active component, which is an indicator of the modern conditions of the entire coastal form development. According to the features of coastal processes taking place within the distal end, they are divided into progradational, dynamic-stable and retrogradational.
The Dzharylhach distal end represents the extreme eastern part of the spit, which has the shape of a hook on the outside and consists of coastal landforms of different genesis and age. An underwater shaft of small size is spread along the distal end front, which passes into a shoal, characterized by a significant drop in depth, which indicates the progradation of the spit’s body.
According to the morphological structure, three components are distinguished within the distal end: a triangular base, an isthmus, and an expanded headland. Offshore bars of different ages are located within the triangular base. The ancient offshore bars are oriented from the southeast to the north-northwest, that is, they have a diametrically opposite direction with similar forms of the wide part of Dzharylhach.
The distal isthmus and expanded headland are new Dzharylhach generations, which were formed over the last hundred years. The surface of the isthmus has a concave character, which is due to the presence of fans of overwashes and splashes. Arcshaped generations of modern offshore bars and swales, as well as lakes of lagoon origin represent the extended distal end.
The quantitative parameters of the distal end dynamics presented in the work indicate the specific conditions of its development, under which the narrow part is actively eroded, and the expanded part increases and moves towards the sea. It should be noted that similar conditions also took place in the areas of the distal extremities of the Bakalska (the Black Sea) and Obytichna (the Sea of Azov) spits. Because of the narrowing, breaches were formed at the site of the isthmus, and the headlands turned into islands.
Conclusions. Morphological features and morphodynamic trends of the distal end testify to the transformation of lithodynamic conditions within its limits. The presented studies allow us to state that the indicated distal end is not the discharge zone of a single alongshore flow of sediments directed from west to east. This is primarily evidenced by the morphology of the distal end underwater slope, within which there is only one local offshore bar, which is not connected with similar formations spread along the front of the spit.
The Dzharylhach spit distal end development is due to the interaction of alongshore and transverse sediments transport, which are manifested against the background of human-complicated conditions of the coastal zone. In our opinion, there are two local lithodynamic cells within the distal: frontal and rear. The front one is characterized by the transport of debris material from the front of the isthmus to the loop-shaped spit, and the rear one is from the back side of the isthmus towards the leaned spit.
According to the morphological structure, three components are distinguished in the distal part: a triangular base, an isthmus, and an expanded head. The presented materials allow us to assert that the development of the distal Dzharylgach Spit is caused by the interaction of alongshore and transverse transport of sediments, which are manifested against the background of human-complicated conditions of the coastal zone.