Natural disasters associated with exceeding the usual level of river water occur periodically. In this article, we will find out when we can talk about floods, and when - about floods. We give a definition of each phenomenon and find out the reasons for their origin.
When and why flood occurs
The meaning of the word “flood” as originally Russian, well-aimed and superbly interpreted by the famous Vladimir Ivanovich Dahl in the modern interpretation means the annually repeated seasonal flood of rivers, which is a consequence of the spring melting of ice, snow, and rain. This is a rather lengthy process, causing a significant rise in the level of the river, accompanied by its exit from the channel and flooding of the floodplain.
It is scientifically determined that high water is the highest water content of the river in a year, periodically repeating in the same seasons. This period usually accounts for a large share of annual runoff, sometimes up to 75-80%. The time opposite to the flood is low water - the period of the lowest level. Throughout the year, rivers of a certain type, regime and nutrition, depending on the climatic characteristics of the area, undergo a regular change in periods of high and low water.
Flood seasonality
Intensive spring melting of snow and ice causes a spring flood, accompanied by a rapid and large influx of water. This phenomenon after winter is characteristic of many rivers with snow feeding flowing on the plains. In the life of mountain ponds, a rise in the level is more often caused by the summer melting of glaciers and snow in the mountains.
Consider the seasonality of floods of rivers flowing in Russia, determine the nature of their nutrition and mode.
The rivers that work their way through coniferous, deciduous forests, taiga and grassy steppes along the Russian Plain are dominated by snow food. Since the most intense melting of snow occurs in March-April, therefore, an increase in the level occurs at the same time. Spring flood is a rise in water, which is observed not only on Russian rivers, but also in Poland, Canada, Alaska and the Scandinavian countries. Starting after the establishment of positive average daily air temperatures, it first slowly raises the water level. Then the rate of increase increases to half a meter per day. Soon, water rises on medium and small rivers up to 2-3 meters, on large - up to 20 meters. Spill in width sometimes reaches 15-30 km. The recorded record of rising river levels corresponds to a mark of 60 m on the Yangtze River in 1876.
In the south of Russia, in the steppes and semi-deserts, we can talk about the rain nutrition of water bodies. However, the greatest amount of rainfall in these places also falls in the spring, and flood occurs at the same time. In the continental climatic zones of Eastern Siberia, rivers are characterized by snow nutrition and spring floods, which, due to the climatic characteristics of the region, occur somewhat later in May. And in the monsoon climate of the temperate latitudes of the Far East, there is always an arid winter and a wet, rainy summer. Therefore, the rivers in these territories are dominated by rainwater with summer water rise.
In other words, flood is a natural feature of those natural zones in which rivers flow.
Flood duration
On small rivers, the flood does not last more than 20 days, reaching the highest level on the 3-5th day. Its duration on large rivers reaches 2-3 months, and the peak rise - on the 20-30th day. As a rule, the decline of water lasts 3-5 times longer than its increase. High water on rivers in temperate climates is accompanied by exemption from ice cover. Ice drift continues in small reservoirs for up to 5 days, in large - up to 15.
What is a flood?
It is considered to be a completely different phenomenon. Since it is impossible to foresee the regularity of natural events, the flood, which is their consequence and represents a short-term rapid rise in water level, is irregular and irregular. In other words, in contrast to floods, floods can occur at different times of the year. They are not connected in any way with the regular life processes of water bodies and can be caused by rains or snowmelt at any time of the year. Monsoon rains occurring, for example, in Southeast Asia, can cause river spills more than once a year. The duration of the flood is small - from a couple of hours to several days.
Flooding: flood or flood effects
Thus, high water is an annually repeating pattern on flat rivers in the spring, due to melting snow, and the flood is the rapid rise of water in the same reservoirs in the summer after unexpected heavy rains.
In fact, the rise of water - neither regular nor unforeseen - is not a flood. The consequences that cause high water and high water, i.e., flooding of the area, which may occur due to rising water levels in the river, will be called that. The rise of water that caused this phenomenon can be classified differently depending on the degree of regularity, expectation, or randomness.