What is the main purpose of regrading a failed slope to stabilize it?

The primary purpose of regrading a failed slope to stabilize it is to reduce concentrated flow. When water flows down a slope, it can erode the soil, leading to slope failure. By regrading, the slope can be reshaped to encourage even distribution of water flow across the surface, which helps to decrease the speed and concentration of the water running down the slope. This redesign can help prevent further erosion and mitigate the risk of additional slope failures.

In contrast, adding fill at the top of the slope, removing soil, or removing vegetation may not directly address the underlying issue of water flow and erosion. Adding fill does not necessarily solve the problem of erosion, and can potentially increase the weight and stress on the slope. Removing soil from the top of the slope might destabilize it further rather than providing support. While vegetation plays an important role in preventing erosion by stabilizing soil with roots, the act of removing vegetation could actually exacerbate erosion problems if not properly managed. Therefore, reducing concentrated flow through regrading is a targeted and effective approach to stabilize a failed slope.