Chapter 9.2 Stream Development

Moving Water Carves A Path For streams to form there must be a large source of water. In Temperate areas there is precipitation that occurs on a regular basis. Headwaters: Where water accumulates to supply a stream. Stream channel: Narrow pathway carved into sediment or rock by the movement of surface water. Channels widen with more water Stream bank: Ground bordering each side of a stream that keeps moving water confined. Headward erosion: When small streams erode away the rock or soil at the head of a stream.

Formation of Stream Valleys The stream erodes a path into the rock creating a v- shaped channel. V-shaped channels can become canyons or gorges The stream keeps eroding until it gets to base level, which enters another body of water. The lowest base level is sea level. The V-shaped channel later erodes into a broad valley with gentle slopes.

Mending Streams As a stream channel starts to get wider and get more of a U-shape it is able to hold more water and sediments. The water in the stream usually erodes the sides of the channel so that it becomes wider. Mender: Curve or bend in a stream The center of the stream flows much quicker them at the sides of the stream, because the sides of the stream are effected by friction. The area of a stream that leads to an ocean or a large body of water is called a mouth.

Deposition of Sediment When streams lose velocity, they lose ability to carry sediment. This is due to alluvial fans, which are sloping depositional features formed at the bases of slopes and mainly composed of sand and gravel. This is also due to deltas – silt and clay particles that form triangular deposits when a stream enters a large body of quiet water.

Rejuvenation Rejuvenation: The stream actively resumes the process of downcutting towards its base level. Rejuvenation causes the stream to flow much more quickly. ^ causes streams to form into a V-shape. If rejuvenation occurs where menders are , they form deep sided canyons.