A stream's ability to erode depends mainly on its speed. The water in a mountain stream moves quickly because it is flowing down a steep slope. Fast streams carry more sediment than slow streams of equal size. Fast streams can also carry large sediment grains. As a stream flows toward the sea, its slope decreases. This can make the stream move more slowly, causing larger sediments to settle on the stream bottom.
Features Formed by Water Erosion
Erosion by flowing water reshapes entire watersheds—all the land along and between streams and rivers. Water erosion forms V-shaped valleys, waterfalls, meanders, and oxbow lakes. Figure 14 shows the features formed along the course of a river.
V-Shaped Valleys
Near a stream's source, the stream flows fast as it plunges down steep slopes. As a stream erodes the rock of its streambed, it causes the valley's sides to become steeper. Mass movement on the stream slopes causes a V-shaped valley with sharply angled sides to form.
V-shaped valleys often contain rapids and waterfalls. A waterfall may develop where a stream crosses rock layers that differ in hardness. The harder layers resist erosion, forming the top of the waterfall. The softer rock layers downstream are worn away, leaving the cliff over which the waterfall tumbles.
How do waterfalls form?
Figure 14 As a river winds its way from the mountains to the ocean, it changes the surrounding landscape through erosion and deposition.
Comparing and Contrasting Which features formed by river erosion typically form near a river's source?
For: Articles on Earth's surface: weathering, erosion, and deposition
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