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 relief form - a river valley, one of the elements of which is a floodplain.
What is a floodplain? How is it organized? 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 within very wide limits - from several tens of meters to several kilometers. There are floodplains whose width reaches forty kilometers.
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 channel (see diagram below). Above it are floodplain terraces, the number of which depends on the size and degree of development of the river valley itself.
Floodplains can be seen on almost all natural watercourses - both plain and mountain. 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. Some trees willingly grow here - willow, gray and black alder , fluffy birch. Sometimes these breeds form mixed floodplain forests, in which a large number of different species of birds live.
So, in general terms, we found out what a floodplain is. Next, we will talk about its structure and main types.
Floodplain structure
In the structure of the river floodplain, several smaller relief forms can be distinguished. It:
- Arcuate elongated ridges - the so-called "manes."
- Alluvial braids that separate the floodplain from the constant flow of the river.
- Remains of the hills.
- Old troughs.
- Single boulders and groups of stones.
The floodplain is not a "dead" relief form, since the process of its formation takes place almost continuously (especially intensively during the spring floods). During its floods, the river leaves a fresh layer of silt and soil on its surface. Due to this, 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. It is based on the process of floodplain development and the nature of its deposits. So, N.I. Makkaveev identifies three main types of river floodplains:
- The riverine ones are the most elevated floodplains, separated from the river by a high riverine rampart.
- Central - located in the central part and differ in the most level surface.
- Terraces are the most lowered floodplains located near the slope of the river valley.
Based on the geological structure, floodplains are:
- Basement (with a layer of alluvial sediment of low power).
- Accumulative (with a sufficiently powerful layer of alluvium).
Finally…
What is a floodplain? In simple words - 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.