Stability of Different Coast Types of Lake Onega

Abstract

Comparison of the calculated profiles of dynamic equilibrium and the actual profiles of the underwater coastal slope showed that the majority of the shores of Lake Onega are characterized by poor stability. The profiles of the underwater coastal slope were obtained as a result of field work, including depth measurements and analysis of particle size distribution of bottom sediments along the profile line. Dynamic equilibrium profiles were obtained using the Dean-Brown formula, taking into account the prevailing size of bottom sediments. Previously, 7 morphogenetic types of shores were identified along the Onega Lake shores: poorly altered, abrasive, erosional-aggrading, aggrading, deltaic, lagoonal and technogenic. For various reasons, slightly modified and accumulative types can be considered relatively stable, but their stability is noticeably reduced due to an increase in the water level of the lake, which was about 0.5 m in the 20^th century. Erosional coasts are the least stable. Weakly altered shores are common in the Northern Prionezhye, aggrading shores are found in the Southern and Eastern regions. Erosional shores predominate in the Western Prionezhye, and fragmentarily occur in the Eastern one. Instability and active dynamic processes characteristic of a significant part of the shore, cause long-term risks for their economical, in particular, recreational use.

Studies of the degree of coastal stability depending on their type by comparing the actual measured profiles of the underwater coastal slope with the constructed profiles of dynamic equilibrium are relevant for all the shores of seas and large inland waters, especially those that are intensively used by humans. This method of research allows us to identify sections of the shore with the least long-term risks for infrastructure facilities.