Deltas and Estuaries Flashcards
Deltas and Estuaries
What is a delta?
A discrete shoreline protuberance (It sticks out)
What are deltas important?
Provides storm protection
Influences on delta development
-Water
-Sediment
-Marine Processes
Delta Plain
- Channels and levees
1. Swamps
2. Marshes and bays
Delta Front
- Channels meet ocean
1. Sand/ Sandbars
Delta Front processes
-Rivers carry sed. As bed load (Coarser) and suspended load (Finer)
-Deposition by river slowing
-Forms prograding deposition
Prodelta
Clay and mud deposits
Factor Affecting delta front
-Inertia
-Buoyancy
-Bottom Friction
Inertia
-Shallow plume
-Turbulence slows plume
-Deposition seaward of channel
Bottom Friction
-Bottom friction rapidly slow water
-Deposition at channel
-Water spreads laterally
Buoyancy
-Fresh water over marine water
-Secondary flow created
-Narrow linear bar
-More seaward
Delta Classification
-River
-Wave
-Tidal
River processes
-Seaward transport
-Features
1. Extends seaward
2. Bifurcating channels
Wave processes
-Shore parallel transport ( a longshore current)
-More sandy
-Features
1. Smooth shoreline
2. Few channels
3. Shore parallel (Spits and beach ridges)
Tide processes
-Shore - perpendicular transport
-More muddy
-Features
1. Tidal ridges
2. Many channels
3. Funnel shape
Delta Cycle
- Delta Plain Aggradation
- Shelf Progradation
- Capture of channel elsewhere
- Beaches (rework delta front)
- Barrier island (sinking
- Shoals (Sinking)
Why did many of the major deltas form from 7 to 5 kya
Sea level slowed down 7 kya, so sediment built up
What is an estuary?
A flooded river valley
Why are estuary important?
- Protect land from storm surge
- Good farm land
- Nursery for marine life
Divisions of an estuary
- Head
-Riverine processes and sandier sediments - Main estuary
-Traps sediments and muddier sed. - Mouth
-Ocean processes and sandier sed.
Flocculation
-Attraction of neg. Clays w/ positive salt ions
-Larger particle, faster setting
Describe a wave estuary
-Mouth bar
-Narrow entrance
-Ebb/ Flood delta
Describe a tide estuary
-Large entrance - V shape
-Tidal sand banks
What is the typical stratigraphy of estuary?
-Finning Upward
1.Marsh mud
2.Over tidal flat mud and sand
3.Over channel sand
