Rattlesnake
Creek, southwestern Wisconsin
The plowed cornfield in the center of this photo is the floodplain of
Rattlesnake Creek, seen in the foreground. During floods, the entire field
is covered with water, as shown in the next photo.
Identical view to the previous photo, following a rainstorm of several inches (15 June 1991). Note turbulent flow in the foreground where the stream channel is located.
The floodplain of the Mississippi River is several miles wide at this location on the Wisconsin-Iowa border. Notice the many fluvial features that can be seen on the floodplain.
Natural levees are apparent along this stream. On the far bank, the levee is vegetated, while the plowed field is on the floodplain, slightly lower in elevation. In the foreground, the surveying instrument sits on the natural levee.
This vantage is from a hill, overlooking the floodplain of the Pecatonica River, which flows along the treeline in the center of this image. The trees are growing along the natural levee, while the floodplain is plowed for planting. The standing water at the base of the hill is the poorly-drained backswamp.
Notice the cutbanks, point bars, cutoffs, and oxbow lakes on the floodplain of this meandering river.
A more subtle terrace can be seen here. The floodplain occupies only the low surface immediately adjacent to the stream channel. A higher surface--the terrace--can be seen at the periphery.
This stream is deeply incised into its alluvial deposits, having formed the terraces visible on either side of the channel, approximately 110 feet above the present channel. The incision (down-cutting) of the channel occurred between 1880 and 1885 in response to land use changes and intense rainfall events.
Notice the extensive terraces along this river.
In the foreground of the Teton mountains lies the Snake River, flowing through the forest in the center of the photo. Notice that the forest is growing on the floodplain, while the lighter-colored sagebrush in the foreground is on a terrace approximately 20 feet above the present river channel. The terrace scarp can also be seen on the far side of the floodplain forest.
Mississippi River Lock and Dam #4 on the Wisconsin-Minnesota border. There are 29 such structures on the Upper Mississippi River. The dams raise the water level to allow larger barges to navigate the river, while the locks allow barge passage around the dams from one “pool,” or reservoir to another.
Ground view of an old timber wing dam on the Missouri River. This structure was originally built into the Missouri River channel. Since construction, sedimentation has substantially extended the floodplain, while the river channel has become narrower and deeper.
Aerial view of the Missouri River, showing wing dams. These rock structures are built from the floodplain into the river channel, promoting slow river velocities, low energy, and sediment deposition on the edges of the channel. The center of the river channel has higher velocities, greater stream power, and scours the channel deeper. This allows for passage of larger barges, but is also responsible for loss of floodplain habitat.
The “Big Thompson” is a hydraulic dredge used to remove sediment from the bottom of the Mississippi River navigation channel and pump that material to storage sites. This technique is used to maintain minimum depth needed for barges in areas prone to sedimentation.
Dredge spoil disposal site. Sand and other materials removed from the channel bottom are left in designated disposal sites along the river. Some concerns exist over impacts on floodplain habitats.
Aerial view of barge navigating the Missouri River channel. The modern river channel has lost most of its natural characteristics and now resembles an efficient barge canal. The original channel was much wider and shallower, with sand bars, side channels, floodplain wetlands, and other diversity.
During the “Great Flood of 1993,” flood control levees along the Missouri River failed in places where the river’s energy could not be contained. Notice the scour hole in the floodplain downstream of the meander bend.
Scour hole at levee break. When earthen levees are breached, water quickly erodes a hole in the levee and scours into the floodplain. Such scour holes were often 50 feet deep, with removed material deposited elsewhere on the floodplain.
