The answer to 'why is my drainage system eroding' is that there are several common causes, including improper drainage system design, blockages, and excessive water flow. Symptoms can include standing water, soil erosion, and damage to landscaping or structures.
Some key solutions include cleaning out debris, repairing any broken or damaged drainage pipes, and ensuring the system is properly sized and sloped to handle the water flow. In some cases, you may need to add additional drainage components or redesign the system entirely. If the issue is severe or you're unsure of the cause, it's best to call in a professional landscaper to diagnose and fix the problem.