1. Introduction
Creating reservoirs is known to develop and support several industries:
i.e. electricity, agriculture, water transport, fisheries, recreation
and tourism. At the same time, their creation leads to a fundamental
restructuring of natural systems: river water flow and regime, bedload
and suspended sediment yield are changed, a unique microclimate is
created and landscapes are transformed (Yermolaev & Usmanov, 2014;
Yermolaev et al. , 2015; Nicu et al. , 2019). The intensity
of exogenous processes acting on the shore and banks increases by orders
of magnitude due to the water surface area increase. This very complex
of relief-forming processes (together with erosion and gravitational
processes) is often called bank transformation when dealing with water
reservoirs. Among all modified shores of water reservoirs in Russia,
approximately 78% are destroyed by abrasion type, and the remaining
22% – by abrasion-landslide, abrasion-karst, and other types of
erosion processes (Usmanov et al. , 2018; Gafurov & Yermolayev,
2020). When the banks are destroyed, a large sediment volume enters the
reservoir. This leads to rapid siltation, reduction of water depths, and
environmental degradation of the reservoir.
Exogenous geomorphic processes and their monitoring on the shores of
water reservoirs have long been conducted (Degraff et al. , 1980).
A large number of different research methods have been used for this
purpose (Scaioni, 2015). Most often, the shoreline bank dynamics are
evaluated, and there is limited quantitative data on the different
exogenous processes, their intensity, and the particularities of soil
transport on slopes. This is mainly due to poor field accessibility for
making observations at the shoreline banks and for installing a
reference point network (steep banks, high water level near the shore,
bank collapse, crumbling, and landsliding). New opportunities for
assessing the rate of shoreline modification by exogenous processes,
particularly for shoreline areas that previously were difficult to
access have emerged with the appearance of new instrumental methods
(laser scanners, UAVs, remote sensing, etc.). Simultaneously, a large
diversity of water reservoir types and natural-anthropogenic conditions
shaping their banks has resulted in a specific spectrum of exogenic
processes. This makes data generalization and spatial extrapolation
difficult.
The objective of this study is to better understand shoreline and bank
dynamics of the Kuibyshev reservoir – one of the largest reservoirs in
the world. Research focuses on shoreline abrasion and landslide
processes as the most significant exogenous natural hazards of bank
modification. Attention to these processes has increased because a
significant number of settlements, religious buildings, cattle burial
grounds, and infrastructure (oil and gas pipelines, roads, power lines,
etc.) located on the reservoir shores. The shoreline abrasion and
landslide processes on the banks near settlements often leads to
emergencies: i.e. destruction of buildings, infrastructures,
communications, disturbance and total loss of (agricultural) lands
bordering the reservoir. Shore transformation processes are still going
on at a high rate even though the engineering project predicted the
attenuation of these processes in 20 years after the reservoir creation.
In this connection, it is necessary to develop effective methods to
monitor these dangerous exogenous geomorphic processes. The objective of
this study is therefore to assess quantitatively the rates of shoreline
abrasion and landsliding using modern instrumental methods. The study
sites for shoreline process dynamics were selected by the Ministry of
Natural Resources and Ecology of the Russian Federation and the Federal
Agency for Water Resources. These government agencies identified areas
of the Kuibyshev reservoir banks with the most significant exogenous
natural hazards for human settlements and infrastructure.