Which method is recommended to protect slopes from erosion due to stormwater runoff?

Employing a channel, flume, or slope drain is recommended to protect slopes from erosion due to stormwater runoff because these methods are specifically designed to manage and redirect water flow efficiently. By channeling the water away from vulnerable slope areas, these structures can help prevent the accumulation and kinetic energy of runoff that would otherwise lead to soil disturbance and erosion. They create a controlled pathway for stormwater, guiding it safely without allowing it to saturate or destabilize the slope's material.

In contrast, while using vegetation can help stabilize soil over time, it may not be sufficient as a standalone method in areas with heavy rainfall or significant runoff. Vegetation takes time to establish and might be less effective in the short term. Building a retaining wall can be effective in stabilizing steep slopes but does not directly manage water runoff, which can flow over or around it and continue to cause erosion. Excavating deeper trenches could potentially exacerbate the erosion issue by increasing instability in the surrounding areas and allowing more water to pool, contributing to runoff problems instead of alleviating them. Thus, using a channel, flume, or slope drain is the most comprehensive way to address stormwater management in relation to slopes.