Mississipi Delta Flashcards
What is a delta?
A fan shaped deposit of sediments at the mouth of a river
Size of the Mississipi delta and its background
For the last 7000 years the mississipi river has been depositing sediment from 31 states
The Mississipi delta is 320 km long from Minnesota to the gulf of mexico
Roughly 7000 square miles large
How does tidal range and wave energy influence the formation of the mississipi delta?
The gulf has low energy waves and low tidal ranges which leads to a high level of deposition
Importance of Natural levees in the mississipi delta
- Early communities built on the naturally formed levees
- When the river broke through the levees, sediment and freshwater was deposited on surrounding wetlands protecting communities from storms and creating habitats for animals
Facts about wetlands in the mississipi delta
40% of wetlands of the 48 lower states are found in the mississipi delta
High in biodiversity
Under threat from human activity
Under threat from global warming - eustatic change is threatening low lying wetlands
What land formations are found at the Mississipi delta?
Depositional landforms such as:
- Barrier islands - Chandeleur islands
- Spits and beaches
- sand dunes
- bars
- tombolos
Human factors changing the delta over time
Since the 20th century sediment supply has decreased from 400 million tonnes a year to 145.
Upstream dams, levees and channel engineering has caused louisianna to lose 1900 square miles of land since the 1930s
How have artificial levees impacted the mississipi delta
Artificial levees are used to control the river and protect the communities
- However levering cuts the tie between sediment filled rivers and the delta - preventing the growth of the delta
What are the effects of oil rigs and onshore wells on the mississipi delta
There are 1000s of oil rigs and onshore wells
- this has affected 1000s of acres of wetlands
It has also led to the contamination and damage of shorelines reducing biodiversity and damaging habitats. Also increasing land loss over time due to land subsidence
BP oil rig explosion spewed 206 million gallons of oil into the gulf
Impacts of the BP oil rig explosion 2010
Destroyed hundreds of miles of delicate shoreline reducing biodiversity and damaging habitats.
Thousands of acres of coastal marsh were damaged, disrupting the communities, economy and wildlife of the gulf.
How do upriver dams impact the mississipi delta?
Sediment is trapped behind dams upriver in the mississipi
Since 1850 the amount of sediment reaching the delta has decreased by 70%
How do shipping canals impact the mississippi delta?
Has led to salt water reaching freshwater wetlands, destroying the freshwater ecosystems
How do rising sea levels impact the mississipi delta?
Rising sea levels and susidising land means the threat of thee submergence of coastal Louisiana and the delta is high
How are coastal landforms inter-related on the missippi delta?
- Transport sediment for Chandeleur islands -> provided by beaches
- LSD -> lead to drift aligned beaches
- Spits can often form salt marshes
- Tombolo link barrier islands to beach
