Depositional features of a river

Depositional features of a river

1. Delta

   • Types of delta
     • 1. Accurate
       • Rounded, with convex edges
       • Long-shore drift keeps its shape
       • Example, is the River Niger Delta, Nigera
     • 2. Cuspate
       • Material is spread evenly
       • Example, is the River Ebro Delta, Spain
     • 3. Birdsfoot
       • Sediment load of the river is large
       • Coastal area empties its load, and gains a small tidal range with weak currents
       • Example, The Mississippi Delta , USA
   • Formation
     • Deltas will only form when, the rate of deposition, exceeds the rate of sediment removal
     • Located at the mouth of a river
     • Floccuation occurs as the fresh water, mixes with the seawater
     • Factors influencing the formation
       • The amount/type of sediment available
       • Changes in coast level
       • Volumes of water discharge
     • Deltas are made of three beds
       • Topset bed
         • formed when the river first losses its velocity, and made of larger heavier materials
       • Forest Bed
         • Median graded particles which have travelled a little further before being deposited
       • Bottomset bed
         • Made of the finest particles, which have travelled the furthest before being depostited

2. Levees

   • Cannot form in the upper course of the river, as there is not enough sediment/discharge
   • One of the cheapest ways to protect against flooding
   • Levees can break if the river increases, this can lead to devastating impacts

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