Environmental Engineering Reference
In-Depth Information
FIGURE 7.24
Stereo-pair of aerial photos of a meandering river. Apparent are abandoned channels, oxbow lakes, point bars,
and back swamps. The river enters the ocean on the left and ancient beach ridges are apparent in the lower
portion of the photos (scale
≈
1:40,000).
meandering these point bar deposits remain as sand islands. As the channel migrates, a
sequence of formations begins.
Sandy bars are deposited during high water, and swales filled with fine-grained soils
remain between the bar and the bank. As the river continues to migrate, a succession of
sandy bars and clay-filled swales remain as illustrated in
Figure 7.25.
In the lower
Mississippi River valley, in the late stage of development, swales reach depths of 30 to 60
ft (Kolb and Shockley, 1957).
Oxbow lakes and clay plugs:
As time passes, the meander curve grows until a narrow neck
separates two portions of the river. Finally, the river cuts through the neck, leaving an
