Difference Between Delta and Estuary (With Table)

If you have studied geography carefully during your school days, you must remember coming across terms like delta and estuary. Both the terms are associated with rivers and large water bodies such as oceans and seas. Although for a layman, deltas and estuaries would appear to be similar, there are certain important points of differences between the two.

Rivers commence from the mountain ranges and end up at the seas or oceans. The point where it meets the ocean the speed of the river diminishes, which restricts the ability of a river to carry various sediments any further.

Delta vs Estuary

The difference between Delta and Estuary is that delta is the point where a river is about to meet a sea or an ocean, it drops all the sediments which form a low triangular area of alluvial deposits. Estuary, on the other hand, is somewhat similar to some extent. It is also associated with rivers and oceans or seas.

However, an estuary is a coastal water body or rivers that meet a sea or an ocean and form a transition zone between the two water bodies. In other words, an estuary is formed in regions that experience rift valleys and high tides.


 

Comparison Table Between Delta and Estuary (in Tabular Form)

Parameter of ComparisonDeltaEstuary
DefinitionIt is a low triangular-shaped fertile area consisting of alluvial deposits brought in by a river before meeting a large water body.It is just an area where the fresh water from a river meets the saltwater of seas and oceans.
FormationFormed when rivers fail to carry along the sediments any further due to reduced current before meeting an ocean or a sea.It is formed by a tidal bore that gradually erodes the riverbed and also carries the fertile soil or silt to the sea.
FertilityIt is extremely fertile.It is not very fertile.
TypesBird’s foot, cuspate, and fan-shaped or arcuate.Tectonic estuaries, fjord estuaries, and coastal plain estuaries.
Where it is formedForms in regions that experience coastal plants and low tides.Forms in regions that experience rift valleys and high tides.
Suitability for habitation and agricultureAlthough it is a flood-prone zone, it is extremely suitable for agriculture due to the fertile sediments.Not suitable for agriculture but good for wildlife habitats.
ExamplesGanges Delta and Mahanadi Delta.Baga Creek and Kayamkulam Kayal.

 

What is Delta?

Rivers carry loads of soil and other sediments during their long and tiring journey from the mountain ranges to an ocean or a sea.

A delta or most popularly referred to as a river delta is a landform that is created when sediments, carried by rivers, are deposited at the junction of the river and a larger water body such as a sea or an ocean.

Deltas are normally formed at the meeting points of rivers with seas, oceans, lakes, reservoirs, estuaries, and another river, which is a rather rare situation.

The shape and size of the delta formed are entirely dependent upon by the mere balance between the receiving water body that may either export or redistribute the sediments and the watershed process that acts as the supplier of the sediments.

Different types of deltas are formed. These include wave-dominated deltas, tide-dominated deltas, gilbert deltas, tidal freshwater deltas, mega deltas, and inland deltas.

Some common examples of deltas include Amazon delta, Godavari Delta, Indus River Delta, Rhine Delta, and the Yangtze.

Deltas are extremely fertile, which is why most of the age-old habitats could be found in some of the major delta regions of the world.

 

What is Estuary?

If you think that deltas and estuaries are the same, you need to think again! When you talk about an estuary, it is a limited area of an encircled coastal body of saline water with a minimum of one river flowing into it. It also has a free connection to a sea or an ocean.

It is usually seen that estuaries tend to form a type of transition zone between maritime environments and river environments.

You also need to know that estuaries are easily influenced by various marine influences that include waves, tides, and inundation of salty water to flows of freshwater.

Due to the mixture of freshwater and seawater, a high level of nutrients is formed both in the sediments and water column. Several estuaries suffer from degeneration due to several factors.

These include deforestation, soil erosion, overfishing, filling up of the wetlands, and overgrazing.

Unlike deltas, estuaries are not that fertile and it also has several types that are based on geomorphologies, such as drowned river valleys, fjord type, bar-built or lagoon-type, and tectonically produced.


Main Differences Between Delta and Estuary

  1. Deltas are practically wetlands that are normally formed when a fast-moving river empties its sediments before joining a slow-moving water body such as a sea or an ocean or a lake. On the other hand, estuaries are semi-enclosed water bodies that constitute of salty water. It is normally an area where a river merges with a sea.
  2. Deltas are normally shaped like a bird’s foot or fan-shaped, whereas, estuaries are fjord estuaries or tectonic estuaries.
  3. Deltas are extremely fertile by nature that makes it suitable for agriculture and estuaries are not at all fertile and thus, not suitable for agriculture.
  4. Deltas are formed in regions that experience coastal plants and low tides, whereas, estuaries are formed in regions that experience rift valleys and high tides.
  5. Examples of deltas include Krishna Delta and Brahmaputra Delta. Examples of estuaries include Thekkumbhagam estuary and Baga Creek.

 

Conclusion

Unlike popular beliefs, deltas and estuaries are not the same things at all. Although both are geographical happenings, there are several points of differences between the two terms.

One of the primary differences between the two is the fact that deltas are very fertile and one of the best regions for agriculture.

On the other hand, estuaries are not at all fertile and any type of agricultural attempt at the region will fail miserably.

There are 4 types of estuaries, bar-built, drowned river valley, tectonic, and fjord. However, deltas are of several types such as tide-dominated and wave-dominated.


 

References

  1. https://www.sciencedirect.com/science/article/pii/S0025322705003063
  2. https://link.springer.com/article/10.1007/s11625-016-0355-7
  3. https://www.jstor.org/stable/208680