CIR Interpretation Tutorial
Water Bodies in Virtual Nebraska
The water bodies in the images contained within Virtual Nebraska can be easily identifed by their distinctive color and shape.
Rivers such as the Platte or Niobrara are prominant in many of the images in
Virtual Nebraska. There are several features that one can see which are associated
with the rivers. One can often see white areas along the river. These are
probably exposed sandy surfaces. Lighter toned features within the river probably indicate
either shallow water depth, where the bottom is actually visible to the camera, or else a
place where there is increased turbidity which is caused by silt flowing into the river.
In the case of the Niobrara River seen below, both are evident.
Lakes can either be naturally occuring, or else constructed. The semi-circular feature that is located in the image below is what is called an 'oxbow lake'. It was once a meander of the Missouri River, but was cut-off from the river by the processes of erosion and deposition. Its existence is primarily sustained by groundwater flow.
There are many water or water-related features that are apparent on the landscape that borders Nebraska's Eastern border. Of greatest prominance is the Missouri. Over time this river has followed many courses other than the one it currently does. This is evidenced by the presence of several meander scars. Meander scars are begin their formation as meanders. Meanders are the bends in the river that you can see even in this image. Meanders are formed when the processes erosion and deposition act upon the surface material on which the river flows. As the river begins to "bend", some portions of the river speed-up, increasing erosion on that side of the river, while on the other side of the river, slowing currents allow for suspended material to be fall out of suspension, and thus deposited in the river building up that side. If this process continues on for a long enough time, the meander may become "cut-off". This creates an what is called an oxbow lake. An example of such an oxbow lake can be seen in this image and is named DeSoto Lake. This sort of condition makes for a very interesting political situation, where changing river courses may change the political boundaries between two jurisdictions, in this case the states of Iowa and Nebraska. It was decided some time ago, by politicians from both states, to have the state boundary follow the course of the river at that time. This explains why the state boundary includes DeSoto Lake, and not the new course nearby. Meander scars are created when the oxbow lake gradually fills in with sediment becoming first a marsh and then drying up completely, becoming dominated by terrestrial (land-based) plants rather than by aquatic (water-based) plants.