Delta Formation

• Areas of sediment deposited at the mouth of river• Fast moving water enters a slowing moving body such as sea or lake• Discharge, and therefore competence, reduces dramatically - resulting in deposition of even very fine material• Flocculation occurs when salt water meets fresh water – clays stick together and sink to floor• Highly changeable landforms as sediment is unconsolidated – erosion and incursion by the sea too• Deposition rate must be greater than erosional rate

So – 2 major conditions:• Form on rivers with high sediment rate (Mississippi – 450m tonnes a year)• Rivers flow into bodies of water with little wave action (Nile into the Mediterranean)

Arcuate

• Nile Delta, Egypt

• Rounded, convex margin

Cuspate

• Apalachicola River Delta, Florida, USA

• Tiber, Italy• Material spread

evenly either side of estuary

• ‘Tooth’ shaped

Bird’s Foot• Mississippi Delta,

Louisiana, USA• Many sediment-

bounded channels extending out in a fan shape.