Final answer:
When meander scars are filled with water, they become a. oxbow lakes, which are formed when a river creates a new, shorter course and cuts off a meander bend.
Step-by-step explanation:
When meander scars are filled with water, they are known as a. oxbow lakes. An oxbow lake is formed when a wide meander of a river is cut off, creating a free-standing body of water.
This happens when the river finds a shorter course, cutting through the neck of a meander and isolating the bend of the meander into an oxbow shape. This process is part of the natural evolution of river morphology, as the river erodes its banks and deposits sediment in different locations along its course, including the creation of features like cut banks and point bars.
Further elements associated with river systems include the levee, flood plain, and terrace, each playing a crucial role in the dynamic and complex environment of a river ecosystem.