Delta is Low lying tract of alluvial deposits formed at the river’s mouth
how a Delta Forms
- The speed of the river is checked by sea or lake.
- A heavy load is first deposited.
- Lighter load is carried further into the sea causing that part of the sea to become shallower.
- The part is colonised by plants making it swampy but firmer.
- Plants trap more alluvium making the delta to grow in height.
- The river builds levees making it narrower.
- The river burst its banks and small channels branch off the main river and carries water into the sea or lake (distributaries).
types of river delta
Type of deltas formed at sea.
are deltas that are formed at a lake.
Deltas which form along a rivers course before it reaches the lake or sea.
Formation of inland delta
- The velocity of the river is checked on entering a relatively flat swampy land.
- The river builds up levees.
- The river bursts banks forming distributaries.
- Alluvial deposits are spread over vast areas when river floods e.g. Niger and Okavango deltas.
A delta with a convex shoreline on the seaward end due to strong currents spreading materials over a wide area on seaward side.
Has many distributaries e.g. Tana and Rufiji deltas.
Birds Foot Delta
Type of a delta with a pattern resembling the foot of a bird.
Has few distributaries.
Formed on a river carrying large quantities of fine alluvium into water where there is low wave energy e.g. Omo and Mississippi deltas.
Delta which has formed on an estuary.
Formation of estuarine delta
- The rivers load is deposited on the estuary when the speed is checked by sea.
- The river cuts across in a single channel that may be bordered by levees e.g. on R.Volta in Ghana and on R. Zambezi.