What are the characteristics of a dead river?

Question

What are the characteristics of a dead river?

Answer 1

Rivers are seldom "dead" although with respect to fish life they are.  Excessive pollution with nutrient material from sewage and agricultural runoff can lead to "eutrophication" in which oxygen is depleted by bacterial proliferation in the water, leading to a dissolved oxygen level too low for fish to survive.

In a geological sense a "dead" river can be also be interpreted as a river that no longer exists.  In the geologic record evidence of earlier rivers can be found, which for various reasons ceased to exist.  In a sense oxbow lakes are "dead rivers" since they are former segments of a river that have been  superseded by other drainage patterns.