Quebrada: What is, characteristics and how it is formed

In geography, a ravine is defined as a narrow and deep valley with steep slopes, which is mainly formed in mountainous or pronounced slopes. Its origin is usually associated with the erosive action of water, which is wearing the terrain over time, although it may also be due to tectonic movements.

At the bottom of the gorge, a stream or a river usually flows, permanently or seasonally, depending on the rainfall regime. This water contribution generates special conditions that allow the development of vegetation and different animal species, turning the ravines into ecosystems of great ecological importance.

You may also be interested in reading this article about a river valley: what it is, how it is formed and examples.

The ravines have a series of their own characteristics, such as:

• They have steep slopes and abrupt slopes: the ravines usually have very pronounced earrings with steep slopes. This form of the relief favors the rapid runoff of water and erosive processes, in addition to generating strong contrasts between the regions that reach solar radiation and those that remain in the shadow, thus creating microclimates of very particular characteristics.
• There is a great seasonal variation in the water flow: many streams have streams or water courses that work seasonally. In times of rainfall, the flow increases, while in dry stations it can be reduced a lot or even drying temporarily.
• They present good quality waters: In many ravines, the water that circulates remains relatively clean and little altered by human activity. Studies carried out in different places show that they usually present low levels of nutrients such as nitrogen, indicating poor pollution. In addition, characteristics such as pH, conductivity or amount of minerals depend largely on the type of rocks and soils where water flows.
• They are environments that retain high humidity and allow the formation of microclimates: in the ravines a lot of moisture is preserved, either on the ground, in the vegetation or even is presented as mist. This happens above all in the most closed and shaded parts, where the sun’s rays almost do not enter. Thanks to the presence of these variables, microclimates are generated that allow the presence of species adapted to these conditions.
• They have fertile soils and with greater water retention capacity: in many cases, especially where there is dense vegetation, the floors of the ravines (or their margins) have greater organic matter and better structure, which improves the retention of humidity and nutrients, compared to more exposed slopes.
• They are rich environments in biodiversity: due to the diversity of existing microhabitats (differences in light, temperature, humidity), many streams house a wide variety of species of flora and fauna and even numerous endemic species.
• They intervene in water regulation: the ravines intervene in the collection of water, recover aquifers, shocks runoffs, reduce flood peaks in the lower parts of basins, and act as temporary water reservoirs in heavy rainy episodes.
• They are vulnerable to human disturbances: being pending, with loose slopes, presence of water, wet and fragile soils, the ravines can be very sensitive to different anthropic activities such as deforestation, urbanization, stream contamination, channel modification, etc. This can cause accelerated erosion, landslides and even loss of biodiversity.

The ravines originate mainly due to the erosive action of water over time. When the rains are intense or frequent, the runoff water begins to wear the terrain, opening furrows that, over the years, deepen to form a narrow and encased valley. In many cases, this erosion is favored by the slope of the relief, since in the mountainous areas or with marked slopes the water descends more strongly, increasing its ability to drag sediments and rocks.

Another way in which the ravines can originate is from the tectonic activity, when the movements of the earth’s cortex generate fractures or sinkings in the field that are then used by the water to open their way.

A ravine is a narrow and deep valley formed by water erosion or tectonic processes. That is, it is a type of geographical accident that opens between mountains or steep slopes. At the bottom of that ravine it may or may not circulate water. On the contrary, a river is a fresh water course that flows continuously, more or less caudalous, from birth to its mouth. The river is moving water.

Does a ravine always have water?

Not necessarily. Many streams have streams or rivers that flow only in the rainy season or after storms, while in the dry season they can stay with little flow or even dry. Others, on the other hand, keep the water permanently thanks to springs or the accumulation of frequent rains.

What is the importance of the ravines?

The ravines act as natural runners (biocorredores) that connect different environments and allow species displacement. In addition, they regulate the water flow and allow the recharge of the aquifers. Also, they help avoid flooding and generate microclimates where a great diversity of species thrives. In many cases, they have a high cultural and tourist value.

What flora and fauna live in the ravines?

The flora and fauna of the ravines varies greatly according to the region, climate and altitude. In humid environments, such as those of the subtropical northwest or in areas of Yungas, it is common to find ferns, mosses, lichens, riverside trees and a great diversity of birds, amphibians and insects.

On the other hand, in ravines of arid environments such as the Humahuaca creek, the vegetation is dominated by cardons, xerophytes shrubs and species that support the lack of water and the strong thermal oscillations well. There, the fauna includes birds of dry areas, reptiles and mammals adapted to water stress.

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