Depositional features of a river

Delta
1. Types of delta
  1. 1. Accurate
    1. Rounded, with convex edges
    2. Long-shore drift keeps its shape
    3. Example, is the River Niger Delta, Nigera
  2. 2. Cuspate
    1. Material is spread evenly
    2. Example, is the River Ebro Delta, Spain
  3. 3. Birdsfoot
    1. Sediment load of the river is large
    2. Coastal area empties its load, and gains a small tidal range with weak currents
    3. Example, The Mississippi Delta , USA
2. Formation
  1. Deltas will only form when, the rate of deposition, exceeds the rate of sediment removal
  2. Located at the mouth of a river
  3. Floccuation occurs as the fresh water, mixes with the seawater
  4. Factors influencing the formation
    1. The amount/type of sediment available
    2. Changes in coast level
    3. Volumes of water discharge
  5. Deltas are made of three beds
    1. Topset bed
      1. formed when the river first losses its velocity, and made of larger heavier materials
    2. Forest Bed
      1. Median graded particles which have travelled a little further before being deposited
    3. Bottomset bed
      1. Made of the finest particles, which have travelled the furthest before being depostited
Levees
1. Cannot form in the upper course of the river, as there is not enough sediment/discharge
2. One of the cheapest ways to protect against flooding
3. Levees can break if the river increases, this can lead to devastating impacts

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	Criado por Phoebe Fletcher quase 10 anos atrás