The document discusses different types of river deltas, which are areas of sediment deposited at river mouths where flowing water enters a slower body of water. Deltas form when the river's sediment load deposition rate exceeds the erosion rate in areas where rivers discharge into seas or lakes with little wave action. Common delta types include arcuate deltas with rounded edges, cuspate deltas resembling teeth, and bird's foot deltas with many branching sediment-bounded channels fanning out.

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.