What characterizes incised meanders?

Incised meanders are specifically characterized by meandering channels that occur within steep, narrow, bedrock valleys. This geological feature typically forms when a river or stream cuts deeply into the landscape, creating a pronounced meandering pattern as it erodes the surrounding rock and soil.

The formation of incised meanders is often a result of a combination of changes in base level, such as tectonic uplift or a fall in sea level, which can force a river to adjust by deepening its channel. As the river flows through these steep valleys, it maintains a sinuous pattern while simultaneously incising into the rock. This process produces a landscape where the meanders are entrenched, making them distinct from more gently flowing rivers in broad, flat valleys where meanders do not exhibit such deep incision.

The other options, while they may describe different river characteristics, do not accurately capture the specific nature of incised meanders. For instance, the presence of meandering channels in flat valley bottoms describes a different kind of river behavior, contrasting with the erosion and entrenchment seen in incised meanders. Similarly, straight channels in alluvial plains or channels without significant slopes do not reflect the steep, incised environments where this unique meandering form exists.