The correct answer is: D. All sides.
Scouring is the process of erosion of the sewer pipe wall by the flowing water. It is caused by the high velocity of the water and the abrasive particles that are carried in the water. Scouring can lead to the formation of holes in the pipe wall, which can eventually lead to the collapse of the pipe.
Scouring is more likely to occur on the bottom side of the pipe because the water velocity is highest at the bottom of the pipe. The water velocity is also highest at the corners of the pipe, so scouring is also more likely to occur at these locations.
Scouring can be prevented by using a smooth-walled pipe, by reducing the velocity of the water, and by removing any abrasive particles from the water.
Here is a brief explanation of each option:
- Option A: The top side of the pipe is not as likely to be scoured because the water velocity is lower at the top of the pipe.
- Option B: The bottom side of the pipe is more likely to be scoured because the water velocity is highest at the bottom of the pipe.
- Option C: The horizontal sides of the pipe are also likely to be scoured because the water velocity is high at the corners of the pipe.
- Option D: All sides of the pipe are susceptible to scouring because the water velocity is high at all locations.