River Systems Part 3 Formation of Deltas Flooding

River Systems Part 3 • Formation of Deltas • Flooding

Structure of a simple delta that forms in the relatively quiet waters of a lake. As a stream extends its channel, the gradient is reduced. Frequently, during flood stage the river is diverted to a higher gradient route, forming a new distributary. Old, abandoned distributaries are gradually invaded by aquatic vegetation and fill with sediment.

During the past 6 000 years, the Mississippi River has built a series of seven coalescing subdeltas. The number indicate the order in which these subdeltas were deposited. The present birdfoot delta (#7) represents the activity of the past 500 years. Without ongoing human effort, the present course will shift and follow the path of the Atchafalaya River. The inset on the left shows the point where the Mississippi River may someday break through(arrow) and the shorter path it would take to the Gulf of Mexico.

The Birdfoot Delta of the Mississippi River in Louisiana

The Amazon River Delta in Brazil

The Nile River Delta in Egypt

Rivers Flooding Floods are the most common geologic hazard. Two major causes of floods are: – weather – human interference with the stream system

The Mississippi River Flooding

Satellite view of the Missouri River Same satellite view flowing into the during flooding in 1993 Mississippi River near St. Louis Figure 5. 23 top

The Amazon River Flooding

The Nile River Flooding