Guided Notes on Stream Development

Guided Notes on Stream Development, Section 9.2 1. As a stream develops, it changes in shape, width, and size, as well as the landscapes over which it flows. 2. The first and foremost condition necessary for stream formation is an adequate supply of water. 3. The region where water first accumulates to supply a stream is called the headwaters. 4. Moving water carves a narrow pathway into the sediment or rock called a stream channel. 5. Stream banks are the ground bordering the stream on each side. 6. The process by which small streams erode away the rock or soil at the head of a stream is known as headward erosion. 7. Sometimes, a stream erodes its way through the high area separating two drainage basins, joins another stream, and then draws away its water. This process is called stream capture or stream piracy. 8. As a stream actively erodes its path through the sediment or rock, a V-shaped channel develops. V-shaped channels have steep sides and sometimes form canyons or gorges. 9. The lowest base level possible for any stream is sea level, the point at which the stream enters the ocean. 10. As stream channels develop into U-shaped valleys, the volume of water and sediment that they are able to carry increases. 11. A bend or curve in a stream channel caused by moving water is called a meander. 12. The blocked-off meander becomes an oxbow lake, which eventually dries up. 13. The differences in the rate of water flow within meanders cause the meanders to become more accentuated over time. 14. As a stream approaches a larger body of water or its ultimate end point, the ocean, the streambed’s gradient flattens out and its channel becomes very wide. 15. The area of the stream that leads into the ocean or another large body of water is called the mouth. 16. Streams that lose velocity also lose their ability to carry sediment. 17. A streams velocity lessens and its sediment load drops when its gradient abruptly decreases. 18. Alluvial fans are sloping depositional features formed at the bases of slopes and composed mostly of sand and gravel. 19. Streams also lose velocity and the ability to carry sediment when they join larger bodies of quiet water. 20. The triangular deposit that forms where a stream enters a large body of water is called a delta, named for the triangle-shaped Greek letter delta. 21. During rejuvenation, the stream actively resumes the process of downcutting toward its base level. If rejuvenation occurs in an area where there are meanders, deep sided canyons are formed.