Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.
What Is a Stream Valley?
Next time you see a stream or river, take a minute and observe the water. Look at how fast the water is moving, the direction of the water, and how it has shaped the landscape around the waterway. Running water is very powerful and has the ability to drastically change the landscape around it. Most changes to the land are due to erosion, which is the movement of broken-down rock or soil from one place to another. The running water of a stream helps move particles from their original location to new areas.
When enough land is eroded, a stream can create a stream valley, which is a depression in the earth with water flowing at the lowest point. Stream valleys are also characterized by having a floodplain, which is the wide and level bottom of the valley. Floodplains are important because they designate the areas where the water will fill if the stream floods. Stream valleys can vary by the depth of the valley, the slope of the sides, and the size of the floodplain.
The Formation of Stream Valleys
The formation of a stream valley is a long process. Over many years, the stream valley changes and develops due to an aging process. The aging process of a stream valley has three stages, including youth, maturity, and old age.
The youth stage occurs when a stream is located on an uplifted landmass. There is a steep gradient to the land and this causes vigorous and energetic water flow, which results in downward erosion. Stream valleys in the youth stage are often V-shaped, with steep sides, and they do not have any established floodplain yet. They are also characterized by having interrupted stream flow due to boulders, rapids, and waterfalls.
The maturity stage occurs when the stream erodes the valley and removes the boulders, rapids, and waterfalls. Instead of eroding downward, the stream begins to erode the sides of the valley. The valley gets wider and becomes more U-shaped. The valley becomes smoother and has a less steep gradient, which results in more gentle and slower moving water. A mature stream valley is also characterized by a stream with more sloping sides rather than steep sides. This characteristic leads to the formation of a large floodplain where water can escape if the stream becomes flooded.
During old age, a stream valley has a very low flow gradient and has created a floodplain with extremely broad and gently sloping hills. This results in the stream flowing in a very wide formation over the floodplain. Stream valleys that are in the old age stage are more susceptible to floods because they lack physical barriers to direct water flow and because they carry a large amount of sediment and flow slowly.
Now, let's review stream valleys and how they are formed. A stream valley is a depression in the earth with water flowing at the lowest point. Streams create these valleys due to erosion, which is the movement of broken-down rock or soil from one place to another. The water moves particles from one location to another and changes the land formation around the waterway.
A stream valley goes through many changes over the years and generally follows an aging process. The process begins with the youth stage, which is characterized by a steep gradient, fast flowing water, downward erosion, the formation of a V-shaped valley, and barriers to water flow. The next stage is the maturity stage. This stage is characterized by a less steep gradient, slower flowing water, outward erosion, the formation of a U-shaped valley, and the removal of physical barriers. During the maturity stage is also when the floodplain develops, which is the wide and level bottom of the valley.
The final step of the aging process is the old age stage. This stage is characterized by having an extremely low gradient and having a very broad and flat valley. The waterway in this type of stream valley is often very wide and slow moving. Stream valleys and the aging process they go through shed light on how powerful water is and how large of a role it plays in shaping the land around us. Next time you see a stream valley, try to see if you can figure out what stage in the aging process it is in.
Upon completing this lesson, you should be able to:
- Define stream valley and floodplain
- Describe the three stages of the stream valley aging process
- Explain how the formation of stream valleys is important to shaping Earth's land
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