What phenomenon is described as the powerful and concentrated digging action of flowing water during a flood?

The phenomenon described as the powerful and concentrated digging action of flowing water during a flood is referred to as scour. Scour occurs when fast-moving water exerts force on riverbeds, banks, or other surfaces, effectively removing material from these areas. This process is particularly pronounced during floods, as the increased flow velocity and volume of water can significantly enhance its capacity to carry away sediments and reshape landforms.

In contrast, erosion is a broader term that encompasses the removal of soil and rock from various surfaces through different agents such as wind, water, or ice but does not specifically focus on the concentrated action of floodwaters. Siltation refers to the accumulation of silt and sediment in bodies of water, leading to reduced water depth and potential impacts on aquatic ecosystems. Inundation describes the flooding of land but does not specifically address the process of digging or removing material from surfaces. Thus, the best choice that conveys the concentrated and dynamic nature of this action during a flood is scour.