Delta formation

1. 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)

2. Arcuate Nile Delta, Egypt Rounded, convex margin

3. Cuspate Apalachicola River Delta, Florida, USA Tiber, Italy Material spread evenly either side of estuary ‘Tooth’ shaped

4. Bird’s Foot Mississippi Delta, Louisiana, USA Many sediment-bounded channels extending out in a fan shape.