7. Winter Phenomena (Ice Jam) on Rivers from the Romanian Upper Tisa Watershed in 2006–2017 Winter Season

The paper proposes an analysis of the winter phenomena generated by severe persistent negative temperatures (over two months) and sudden changes in weather, as well as of the effects induced by these phenomena on the anthropogenic and natural environment. In the first chapter of the paper, a selective radiography of the main international and national publications related to the winter phenomena on the watercourses is done, with a focus on natural manifestations of ice jam type. A significant concentration of specialists and studies is noticeable in the Nordic world area or in countries with high mountain areas. Also in the first chapter, it provides information about the studied area—the upper watershed of Tisa River, in general, and the Romanian watershed of the upper Tisa, as a case study, as well as on the monitoring activity of the Romanian part of the study basin. The second chapter is dedicated to the presentation of three major components of this space—the morphological, climatic, and hydric—decisive general conditions for the winter phenomena that occurred on the watercourses. In the third part, and the most extended, the specific conditions of occurrence are analyzed at the level of detail (morphological and morphometric, weather conditions—with special regard to the synoptic, the temperature and precipitation variation in the study period), the anthropogenic conditions of the riverbed influence on the studied river sectors. It also includes an analysis on the rivers state, types of winter phenomena occurred during the December 1, 2016–February 14, 2017 period—where the complex winter chart was a great help in the correlation between parameters and in highlighting the phenomena severity—their evolution, monitoring, and management. At the end of this chapter, the variation of the river water levels reported to the defense levels is detailed, as of great significance in explaining the effects generated by natural occurrences. In the last part, issues related to the effects of the winter phenomena on the anthropogenic and natural environment are presented, with details on the produced damages according to the different categories of affected items. The most important aspect related to the consequences refers to damage limitation and the absence of human victims, due to the prompt, concerted, and synchronized actions of all the involved authorities and institutions.