1. River Systems Part 3
Formation of Deltas
Flooding

2. 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.

3. During the past 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.

4. The Birdfoot Delta of the Mississippi River in Louisiana

5. The Amazon River Delta in Brazil

6. The Nile River Delta in Egypt

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

8. The Mississippi River Flooding

9. Same satellite view during flooding in 1993
Satellite view of the Missouri River flowing into the Mississippi River near St. Louis
Same satellite view during flooding in 1993
Figure 5.23 top

10. The Amazon River Flooding

11. The Nile River Flooding