Source: D4K: “Rivers"
Visit the D4K companion Web site to learn more about Rivers: D4K: “Rivers"
This video segment from IdahoPTV's D4K takes you down Idaho's Snake River as it explains river formation, use, and terminology. What is an inner and outer bank, an oxbow, a meander and what makes rapids, are some of the questions that will be answered.
JOAN CARTAN-HANSEN: Most rivers start with rain or snow. As snow melts or as rain falls, the water collects together and runs downhill. When enough water gets together it's called a creek. Creeks form into streams and streams form into rivers. Some rivers come from springs - underground sources of water that bubble up or spill out.
STEVE: Come aboard. I'm Steve. This is the Thousand Springs stretch of the Snake River. From here it goes through, strike up to the Columbia River in northern Idaho.
JOAN: Rivers like the Snake have two banks - an outer bank is more worn away. The water carries away the rocks and sand, depositing it on the bottom of the river. That's called the river bottom. The water can also deposit the dirt and rocks on the inner bank. This constant moving of rock and dirt is called erosion.
CHILD Have you ever wondered why river rock is so smooth? Well, the river tumbles the rock round and round wearing off all the sharp edges. That's erosion too.
STEVE: These rounded rocks over here are called melon rocks. They came down with the flood being tumbled. That's how they got rounded and they're deposited along the inner bank of the river.
JOAN: The course or path of a river can erode the landscape. Slower moving waters find the easiest way to get around obstacles. That means the river's course can bend and turn. Those bends are called meanders. An oxbow happens when a river bends back on itself forming a 'u' shape and waterfalls happen when a river or stream tumbles over a cliff. And did you know that glaciers are just frozen rivers of ice? Glaciers move very slowly but like a river they can erode away and reshape the land. Over thousands of years a river can carve out a valley, create a canyon or smooth out a plain. Rivers are a powerful force.
STEVE: This is blue heart. Look down, you'll see the springs coming up.
CHILD What causes the sand to bubble?
STEVE: It's the spring water finding its way out and that's how it's coming through the sand. It's bubbling. Blue is actually a grey sand, a real fine sand but with the spring water and the daylight it looks blue. This is the 13th largest spring in North America. This water is always 58 degrees all year long.
JOAN: The flow of the river is called its current. The faster the current, the faster the water moves. Rapids form when the hard rock underneath the river bed slopes up or is tilted. The water flows over that uneven surface causing it to churn, becoming whitewater. Too much water can do a lot of damage. In 1976 when the Teton dam failed millions of gallons of water poured out. The Teton River became a raging wall of water wiping out whole towns. But usually rivers are places of life.
STEVE: That's an otter alright. Don't see too many of them here.
JOAN: Rivers are home to lots of different kinds of fish and birds and other wildlife. People live on the river too. Rivers are used to make electricity and for recreation and if you're lucky enough to go with Steve on this part of the Snake you may just get wet. CHILD: Oh yeah
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