Estuary
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 6, Ch 1 "Locating Places on the Earth"; Class 7, Ch 1 "Geographical Diversity of India"; Class 11, Ch 3 "Drainage System"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"
Meaning
An estuary is a funnel-shaped river mouth where the tide flows in and out. Fresh river water mixes with salt sea water there. Strong tides carry the river's sediment out to sea, so it does not pile up into a delta. Estuaries are common where rivers flow through narrow, hard-rock valleys, as the west-flowing rivers of India do. They make good sites for ports and are rich in fish and other life.
Example
The Narmada enters the Gulf of Khambhat near Bharuch, Gujarat, through an estuary. The Tapi also forms an estuary, near Surat.
Don't confuse with
- Delta: a delta is a plain of sediment that builds out into the sea. The east-flowing Mahanadi, Godavari, Krishna and Kaveri form deltas.
- Lagoon: a lagoon is a shallow body of water that bars or spits have cut off from the sea. It is not a river mouth.
Related concepts
- Alluvial fan
- Distributary
- Delta
- Floodplain
- Natural levee
- Point bar
- Meander
- Slip-off slope and undercut bank
- Oxbow lake
- Braided channel