Valley and Stream Erosion Valleys change and grow over millions of years. Stream erosion digs them deeper and wider. It also makes them longer by eating farther and farther into the uplands where they begin. Where the slope flattens out, the stream slows. Then its water can't carry as much sediment (soil, rocks and other material) and drops it. The sediment builds up and changes the way the stream flows. You can look at stream valleys in two main ways. One way is how the valleys of a stream and its tributaries look on a map. The Bryant watershed's valleys make a tree-like pattern. Each stream valley branches into smaller ones, and these then branch into still smaller ones. This pattern comes from very large cracks hidden in the bedrock lying underneath that direct the flow of water on the surface. Another way of looking at stream valleys is by their shape. At their headwaters, the valleys of Bryant tributaries are V-shaped. The streams cut right down into the soil and rock because they are flowing steeply downward, and so they flow fast. Fast water carries more sediment, which grinds the stream deeper and deeper into the bottom of the V. A V-shaped valley is a younger valley, because it is cutting back into the higher ground where it begins. (means hundreds and thousands of years; means hundreds of thousands, even millions of years!) The Bryant's valley is older where it has already cut pretty far down through the bedrock. There it flows less steeply on its way to join the North Fork. Where it's older, it's broader, and you find the rich, flat bottomlands good for farming. There the stream meanders, year by year slowly moving back and forth across the valley, one side losing, one side gaining land. There the land floods in high water times. That's why the bottoms are also called flood plains. You may notice that it is the outside of a curve that eats into the stream bank. The water flows fastest on the outside of the curve. On the inside curve, the slower water drops its sediment, and the land builds up on that bank. That's where you find gravel bars. Then sycamores sprout. In a few years what was stream bottom has become bottomland Source - http://www.watersheds.org/earth/valley.htm
Valley or stream erosion occurs with continued water flow along a linear feature. The erosion is both downward, deepening the valley, and headward, extending the valley into the hillside, creating head cuts and steep banks. In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is relatively steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain. The stream gradient becomes nearly flat, and lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood, when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone that erodes: suspended abrasive particles, pebbles and boulders can also act erosively as they traverse a surface, in a process known astraction.
Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour. Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times.
Thermal erosion is the result of melting and weakening permafrost due to moving water. It can occur both along rivers and at the coast. Rapid river channel migration observed in the Lena River of Siberia is due to thermal erosion, as these portions of the banks are composed of permafrost-cemented non-cohesive materials. Much of this erosion occurs as the weakened banks fail in large slumps. Thermal erosion also affects the Arcticcoast, where wave action and near-shore temperatures combine to undercut permafrost bluffs along the shoreline and cause them to fail. Annual erosion rates along a 100-kilometre (62-mile) segment of the Beaufort Sea shoreline averaged 5.6 metres (18 feet) per year from 1955 to 2002.
Source -http://en.wikipedia.org/wiki/Erosion#Rivers_and_streams This earth cache is not intended to be overly difficult, but more to get people to stop and appreciate this natural wonder. The Peace River Valley provides immaculate panoramic views year-round. It is worthy of a trip if you have never been. If you go there on your own or you are passing through you will definitely want to stop at any one of the numerous points (accessible by driving or by numerous walking trails) to soak in the views. The coordinates take you to a great place to begin but in all honesty there are countless locations to enjoy this view. In order to claim this earth cache you will need to do two things: 1) determine which nearby road is now closed due to forces of erosion, and 2) what hill is impacting this closure. Optional tasks, but definitely a way to increase the enjoyability of your earth caching adventure: post a picture of yourself, your group, or just the valley in the background, and share something you learned that you didn't know before.