Section 2: Stream Development Streams erode paths through sediment and rock, forming V-shaped stream valleys. K What I Know W What I Want to Find Out L What I Learned

Essential Questions What physical features are characteristic of stream development? What is the relationship between meanders and stream flow? How is the process of rejuvenation in stream development explained? Stream Development Copyright © McGraw-Hill Education

Vocabulary Review New abrasion stream channel stream bank base level meander delta rejuvenation Stream Development Copyright © McGraw-Hill Education

Supply of Water Stream channels The region where water first accumulates to supply a stream is called the headwaters. Falling precipitation accumulates in small gullies at higher elevations and forms briskly moving streams. Copyright © McGraw-Hill Education Stream Development

Supply of Water Stream channels Moving water carves a narrow pathway into the sediment or rock called the stream channel. Stream banks hold the moving water within them. When small streams erode away the rock or soil at the head of a stream, it is known as headward erosion. Copyright © McGraw-Hill Education Stream Development

Supply of Water Stream channels The headward erosion of Stream A cuts into Stream B and draws away from its water into one stream, in a process called stream capture. Copyright © McGraw-Hill Education Stream Development

Formation of Stream Valleys The energy of a stream comes from the movement of water down a slope. The slope of a stream channel is called the stream gradient. The gradient of the stream depends on its base level, which is the elevation at which it enters another stream or body of water. Stream Development Copyright © McGraw-Hill Education

Formation of Stream Valleys The height of a stream above its base level determines how much downcutting energy the stream will have. Stream Development Copyright © McGraw-Hill Education

Formation of Stream Valleys Meanders A bend or curve in a stream channel caused by moving water is called a meander. Water moving along the outside of a meander curve experiences the greatest velocity within the meander and erodes the side of the streambed. Stream Development Copyright © McGraw-Hill Education

Formation of Stream Valleys Meanders Along the inside of a meander, the water moves more slowly and deposition is dominant. After enough winding, it is common for a stream to cut off a meander and once again flow along a straighter path. The blocked-off meander becomes an oxbow lake, which eventually dries up. Stream Development Copyright © McGraw-Hill Education

Add link to Animation from p. 234 here. Meander Formation Concepts In Motion FPO Add link to Animation from p. 234 here. Stream Development Copyright © McGraw-Hill Education

Visualizing Erosion and Deposition in a Meander The meanders of a stream are accentuated by differences in the velocity of water in the channel. Stream Development Copyright © McGraw-Hill Education

Add link to Animation from p. 235 here. Visualizing Erosion and Deposition in a Meander Concepts In Motion FPO Add link to Animation from p. 235 here. Stream Development Copyright © McGraw-Hill Education

Deposition of Sediment When streams lose velocity, they lose some of the energy needed to transport sediment, and deposition of sediment occurs. Stream Development Copyright © McGraw-Hill Education

Deposition of Sediment Alluvial fans Alluvial fans are fan-shaped, sloping depositional features that form when water flows down steep slopes onto flat plains. Alluvial fans are composed mostly of sand and gravel. Stream Development Copyright © McGraw-Hill Education

Deposition of Sediment Deltas The triangular deposit that forms where a stream enters a large body of water is called a delta. Delta deposits usually consist of layers of silt and clay particles. Stream Development Copyright © McGraw-Hill Education

Rejuvenation During rejuvenation, a stream actively resumes the process of downcutting toward its base level. This causes an increase in the stream’s velocity, and the stream’s channel once again cuts downward into the existing meanders. Stream Development Copyright © McGraw-Hill Education

Review Essential Questions Vocabulary What physical features are characteristic of stream development? What is the relationship between meanders and stream flow? How is the process of rejuvenation in stream development explained? Vocabulary stream channel stream bank base level meander delta rejuvenation Stream Development Copyright © McGraw-Hill Education