The Highway Erosion

Erosion often occurred at slope which is common at highway. At the highway there are a few of method to prevent erosion. Failure of controlling erosion can also cause a slope failure which lead to any mass movement. It is known that rain is one of the factors that cause erosion, so how to handle this at highway?
As usual, we are presenting our slideshow.
By that, erosion at slope at highway are need to be prevent, not because of it's threaten the highway itself but the user of the highway too. Can you imagine, when you are using the highway and suddenly a big pile of soil drop on you. Wouldn't it be awful?