Final answer:
Mass wasting events like landslides can block or alter the course of a stream, affecting its discharge, channel roughness, and the size and shape of its bed, leading to changes in streamflow behavior.
Step-by-step explanation:
Mass wasting events, such as a landslide or a mudslide, can significantly alter the flow of a stream. For instance, when slope material becomes saturated with water, it could lead to a debris flow or mud flow. This can block the stream's channel, altering its course, or create a temporary dam that, when breached, could lead to a sudden increase in discharge.
The added material can also increase channel roughness, affecting the stream's velocity, and can change the size and shape of the streambed. The steepening of the gradient during such an event would speed up the streamflow, leading to more erosion downstream. Eventually, the water flow can wade through or around the obstruction, and the stream may reach a new equilibrium with a changed route or modified channel characteristics.