The relief of our planet is the result of a complex effect on the earth's surface of flowing water, wind, gravity and other natural forces and phenomena. The most important role in the design of the "exterior" of the Earth is played by rivers. They form a specific form of relief - a river valley, one of the elements of which is a floodplain.
What is a floodplain? How is it organised? What types of floodplains exist? Our article will tell about all this.
What is a floodplain
The definition of this term is quite simple. The floodplain is a periodically flooded part of the river valley, which is directly adjacent to the channel deepening of the river. Its dimensions can vary over a very wide range - from several tens of meters to several kilometers. There are floodplains that are up to forty kilometers wide.
What is a floodplain in terms of geology and geomorphology? This is a form of fluvial relief (from the Latin word fluvius - stream), the lower element of the valley, located between its slope and the river bed (see diagram below). Above it, there are terraces above the floodplain, the number of which depends on the size anddegree of development of the river valley itself.
Floodplains can be seen in almost all natural watercourses - both flat and mountainous. They do not form only in very narrow canyon valleys. The floodplain, as a rule, has a flat surface. The flora of this section of the river valley is represented by herbaceous plants and hydrophilic shrubs. Willingly grow here and some trees - willows, gray and black alder, fluffy birch. Sometimes these rocks form mixed floodplain forests, which are home to a large number of different bird species.
So, in general terms, we found out what a floodplain is. Next, we will talk about its structure and main types.
Floodplain structure
Several smaller landforms can be distinguished in the structure of the river floodplain. This is:
- Arcuate elongated ridges - the so-called "manes".
- Alluvial spits that separate the floodplain from the constant flow of the river.
- Remnant hills.
- Old troughs.
- Single boulders and groups of stones.
Floodplain is not a "dead" relief form, since the process of its formation is almost continuous (especially intense during spring floods). During its floods, the river leaves a fresh layer of sediments of silt and soil on its surface. As a result, river floodplains are known for their fertility.
Types of floodplains
One of the first scientific classifications of river floodplains was proposed by the Soviet geomorphologist and hydrologist Nikolai Makkaveev. In herThe basis is the development of the floodplain and the nature of its deposits. So, N. I. Makkaveev distinguishes three main types of river floodplains:
- Near-river - the most elevated floodplains, separated from the river by a high riverbank.
- Central - located in the central part and are distinguished by the most leveled surface.
- Terrace - the most lowered floodplains, located near the slope of the river valley.
Based on the geological structure, there are floodplains:
- Socle (with a layer of alluvial deposits of small thickness).
- Accumulative (with a sufficiently thick layer of alluvium).
In conclusion…
What is a floodplain? In simple terms, this is the lower part of the river valley, which is periodically flooded with water (mainly during floods and seasonal floods). River floodplains have their own geomorphological structure and are divided into several types, depending on the geological structure and appearance.
