the river changes throughout its course
course: path of river. upper, middle and lower.
rivers: erode landscape; wear down, transport load, then deposit elsewhere.
shape of valley & channel depends on whether erosion or deposition is dominant process.
V-shaped valley, steep sides, narrow/shallow channel.
Gently sloping valley sides, wider/deeper channel.
Very wide, almost flat valley sides. Wide/deep channel.
Deepens valley & channel, making it v-shaped. Dominant in upper course.
Widens the river valley & channel. Dominant in middle and lower courses.