FYFD

Tag: oxbow lake

  • Forming an Oxbow

    Forming an Oxbow

    Without human intervention, meandering rivers become more sinuous over time. This is driven by the flow around a river bend, which tends to push sediment from the outer bank of the curve to the inner, making the bend more pronounced. Eventually, loops in the river can pinch off and form a separate oxbow lake, as seen in the animation above and video below.

    By studying many photo sequences like this one, researchers have concluded that how quickly a river bend meanders depends on its curvature. In general, the higher the curvature, the faster the river bend will migrate. When rivers deviate from this rule of thumb, it’s typically because part of a river bank is tougher to erode than other sections. (Image and video credit: Z. Sylvester/Geolounge; research credit: Z. Sylvester; via Landsat; submitted by Aatish B.)

  • Meandering River

    Meandering River

    When unconstrained by the local topography, rivers tend to meander, as shown in this astronaut photograph of the Arkansas River near Little Rock, AR. The current course of the river is visible in green in the lower right hand corner of the image, but numerous lakes and curved banks show some of the former paths the river took. When rivers develop a bend, flow is faster on the inner bank than around the outer bank. This speed difference causes a vortical secondary flow inside the river that removes sediment from the outer bank and deposits it on the inner side. The end result is that the bend in the river gets sharper and the river meanders further. Sometimes the bends get so sharp they pinch off, leaving behind lakes. (Photo credit: Exp. 38/NASA Earth Observatory)

  • Meandering Mississippi

    Meandering Mississippi

    This satellite photo of the Mississippi River south of Memphis, TN shows how the river’s course has changed over time. When a river bends, the water near the inner bank flows faster than the water by the outer bank. This difference in speeds actually creates a vortical secondary flow in the boundary layer of the river that erodes sediment from the outer bank and deposits it on the inner bank. This increases the meander of the river bend. If this continues long enough, the river bend can get pinched off into an oxbow lake, like the ones scattered to either side of the current river path.