What Is an Oxbow Lake?
An oxbow lake is a U-shaped or crescent-shaped body of water that forms when a wide meander from a river is cut off from the main channel, creating a freestanding, still body of water.
Section 2: The Formation Process
The process begins with a mature river flowing across a flat plain, creating winding curves called meanders. Erosion on the outer banks and deposition on the inner banks cause the 'neck' of a meander to become progressively narrower. Eventually, during a period of high water flow like a flood, the river cuts a new, shorter channel across the narrow neck, abandoning the old meander loop.
Section 3: A Practical Example
Imagine a river with a large, looping bend. Over many years, the river erodes the land, making the loop's entrance and exit points get closer and closer. During a major flood, the powerful water takes the shortest path and flows straight across this narrow piece of land. After the flood, sediment builds up and plugs the ends of the old loop, separating it from the new river channel and leaving behind a curved oxbow lake.
Section 4: Importance in Ecosystems
Oxbow lakes are ecologically significant because they create calm, slow-moving wetland habitats that are distinct from the flowing river. They support a diverse range of aquatic plants, birds, and other wildlife. Over long periods, these lakes can fill with sediment and organic material, transforming into swamps or marshes before eventually drying up.