What action is taken to mitigate the risk of landslides?

Building catch walls is a highly effective method for mitigating the risk of landslides. Catch walls, also known as retaining walls or landslide barriers, are structures designed to hold back soil and rocks on slopes. When properly constructed, they provide stability to steep terrain by preventing the downward movement of soil during heavy rain or seismic events. The walls can effectively redirect water runoff, reducing the saturation of the soil and preventing erosion, both of which can trigger landslides.

The other options provided may influence the stability of slopes to some extent, but they are not as directly effective in landslide mitigation. Planting trees can contribute to soil stabilization through root systems, but it may take time for the vegetation to establish sufficient roots to effectively prevent landslides. Removing bedrock can actually exacerbate instability rather than mitigate risks, as it can destabilize the surrounding soil. Replacing loose soil with concrete is not a recommended practice because it can lead to other forms of erosion and runoff issues, as concrete can create a hard surface that does not absorb water, potentially increasing the risk of landslides in adjacent areas. Thus, the construction of catch walls stands out as the primary and most effective action for mitigating landscape instability and landslide risk.