• Climate in the Gulf
• The Report
• For Teachers
• Slow the Change
• Speed our Response
• Water Resources
• Sea-Level Change
• Human Perspectives
CONTROLLING A RIVER:
THE MISSISSIPPI RIVER DELTAIC PLAIN
The Mississippi delta region—with big population centers such as New Orleans—represents one of the most vulnerable regions of the Gulf Coast. The combined effects of engineered and altered landscapes, natural subsidence, and climate change will have tremendous consequences for human well-being, natural resources, and biodiversity.
Over the past century, the nearly 1.3 million square mile watershed of the Mississippi River has experienced major environmental changes, including conversion of more than 80 percent of forested wetlands to agriculture and urban areas, channelization, dam construction, and river levees. The construction of massive structures that keep the river from switching channels has restricted sediment and freshwater supply to the flood plain.
Some of these wetland losses are due to delta subsidence (sinking), which results in relative sea-level rise. Although subsidence is a natural process, human interference with river and sediment flow and withdrawal of groundwater have exacerbated it.
Major changes in the upper and lower watersheds of the Mississippi-Atchafalaya river system have also increased the likelihood of low-oxygen conditions (hypoxia) in Gulf waters.
On the Louisiana continental shelf, hypoxia can extend over thousands of square miles, depending on the amount of freshwater discharge, which controls the addition of nutrients and the stratification of coastal waters. Climate model studies predict a 20 percent increase in discharge from the Mississippi River watershed, which could lead to an expanded hypoxic or "dead zone."
Tour another Special Place:
Apalachicola Bay | Big Thicket | Everglades | Laguna Madre | Mississippi Delta
Stork, ibis and herons congregate in the Atchafalaya Basin: USACOE Photo Library
Hayes Pumping Station: USACOE Photo Library, P. Collins
Berwick Lock, LA: USACOE Photo Gallery, A. Belala
London Outfall Canal. New Orleans: USACOE Photo Library, D. Spinks
Cypress-tupelo swamp: USGS, D. Demcheck
• Apalachicola Bay
• Big Thicket
• Laguna Madre
• Mississippi Delta