Delta: What is it, how it is formed and types

A delta is a geographical formation that originates in the mouth of river systems In a body of water, be it a sea, semi -closed sea or lake and that is characterized by the gradual accumulation of sediments transported by the river current.

The deltas usually have large channels with albardones formed by sediments, which contain depressions in which permanent or semi -permanent lagoons are found. These transition environments offer unique habitats that support great biodiversityproviding refuge and food for a wide variety of aquatic species and migratory birds. In addition, they act as natural shock absorbersreducing the strength of the tides and protecting the surrounding coastal areas of extreme climatic events. Also, in the deltas around 500 thousand people are located worldwide, since they provide numerous ecosystem benefits and improve the well -being of human societies.

Deltaic systems are constructive bodies whose formation is closely linked to significant sediment contributionwhich must overcome the redistribution capacity by the receiving basin (for example a sea). The key to its formation lies in the ability of water to transport and deposit these sediments, giving rise to the creation of an intricate network of channels and sand banks. So how is a delta formed?

The suspended sediments vary along the river And they also depend on where it circulates. Upstream the river erodes the substrate and drags the sediments that constitute the load of the downstream river. When the water and sediments transported through the river current reach the mouth, they lose confinement, which translates into a loss of the flow rate and the subsequent deposition of the sediments. The thickest sediments, such as gravels and sands, will be deposited in the most proximal areas, many being trapped by the vegetation located on the margins of the river course. On the contrary, the finer particles travel suspended to more distal areas and are deposited by decantation processes. With the successive discharges of the river they are advancing and contributing sediments to the interior of the basin.

Here we present three types of deltas that are classified according to the dominant process that reigns in them:

Dominated fluvio

The fluvio-dominated deltas are those in which The main influence on its formation comes from the river flow. In this type of delta, the river transports large amounts of sediments, which are deposited in the mouth due to the decrease in water speed when it comes into contact with a body of more extensive water, such as an ocean. The topography and river dynamics play a crucial role in the creation of these deltas, which usually present a network of distributory channels and well -defined sedimentary fans.

Deltas dominated by tides

Deltas dominated by tides are characterized by the significant influence of tides in their formation. In these areas, the tides play a crucial paper when modifying and redistributing the sediments deposited by the river. The action of the tides can result in narrow and deep channels, as well as in the formation of extensive intermareal areas. This type of delta tends to present characteristics more elongated and narrow Compared to fluvio-dominated deltas, since the tides have a continuous impact on deltaic landscape configuration.

Deltas dominated by wave

Deltas dominated by waves are formed in areas where the action of the sea waves has a preponderant influence. In these cases, the waves play a key role in the redistribution of sediments along the coast, contributing to the delta configuration. The energy of the waves can affect the shape and distribution of sediments, and the dynamics of coastal currents can influence the extension and shape of the delta. This type of delta usually exhibits most pronounced features on the coastline, with beaches and sandy bars which are the result of the combined action of waves and currents.

• Delta del Río Paraná: It is a river delta that has 14,000 km² and a length of 320 km, is born in the city of Diamond, province of Entre Ríos and reaches the mouth of the great estuary of the Río de la Plata. It is divided into three regions: the upper delta, the middle delta and the lower delta. It is considered one of the world’s largest deltas.
• Nile River Delta: The Nile River Delta located in Bajo Egypt, flows into the Mediterranean Sea and is considered one of the world’s largest river deltas, since it covers about 160 km long. In it, approximately 40 million people live, being Alexandria the largest city of said Delta.
• Delta del Río Misisipi: It is a fan -shaped geographical accident, located in the state of Louisiana in the United States and is formed by the deposition of detritic materials that the Mississippi river transports. It includes 12,000 km2 of coastal wetlands, which makes it a region of biological importance. It also forms a region of commercial importance.

Now that you know what a delta is, do not miss these other articles on the difference between Delta and Estario and the river erosion: what is, types, consequences and examples.

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