How does water behave when flowing across an alluvial fan?

When water flows across an alluvial fan, it interacts with the fan's coarse materials, leading to significant infiltration. Alluvial fans are typically formed by the deposition of sediment from a river or stream that flows out of a mountainous area onto a flatter plane. The sediments can vary in size, and the larger, coarser materials allow water to penetrate more easily.

As water reaches the alluvial fan, it tends to soak into these coarse materials due to gravity and the porous nature of the sediments. This process is crucial for recharging groundwater and contributes to the hydrological cycle in the area. The distinct characteristics of alluvial fans, with their varying grain sizes and structure, facilitate this absorption rather than promoting surface runoff.

Additionally, while water may initially spread out as it reaches the fan, it does not remain stagnant or flow back toward the mountains due to the slope of the fan. Instead, its primary behavior is to infiltrate the materials, making option C the accurate choice regarding how water behaves in this context.