- How do oxbow lakes form?
- Water flows fastest on the outside of a bend and erodes the bank, so the loop grows wider and tighter. Over time the neck between two loops narrows until the river breaks through a short straight channel. The water then takes the shortcut, and the abandoned loop is left as a crescent-shaped lake called an oxbow lake.
- What is a point bar?
- A point bar is a ridge of sand and gravel on the inside of a meander. The water is slow there, so it drops its load. As the bend migrates, the point bar grows and the river moves away from it.
- Why do rivers meander?
- A river that flows over flat land with some slope starts to wiggle. The flow curves, faster water swings to the outside and erodes it, and slower water on the inside deposits. Each bend then amplifies the next, so the loops grow.
- What are the upper, middle and lower courses of a river?
- The upper course is steep, narrow and V-shaped, with waterfalls and rapids. The middle course widens and the gradient eases. The lower course is flat, with wide meanders, a floodplain, and a delta where the river meets the sea.
- What is sinuosity?
- Sinuosity is the river length divided by the straight-line distance it covers. A straight river has a value of 1, and a strongly meandering river can be 1.5 or more.
- How does discharge change a river?
- More discharge means more water and higher velocity. Faster water erodes faster, so meanders migrate and cut off more quickly. In this tool the velocity is a model estimate, not a measured value.