Final answer:
Undercutting of a bank by its stream can trigger a landslide due to the destabilization of the slope by over-steepening and saturation from moisture.
Step-by-step explanation:
Undercutting of a bank by its stream may trigger a landslide. When erosion by rivers, glaciers, or ocean waves creates over-steepened slopes, the stability of the bank is compromised. Adding to this, rock and soil slopes can be weakened through saturation by snowmelt or heavy rains, which contributes to the slope failure. Landslides encompass various ground movements, including rock falls, deep failure of slopes, and shallow debris flows. Particularly, the saturation of slope material with water can lead to a debris flow, picking up anything in its path and potentially leading to significant damage and flooding.