The answer to 'why is my retaining wall erosion' is that there are several common causes, including poor drainage, soil erosion, and improper construction. Retaining walls are designed to hold back soil and prevent erosion, but if they are not properly maintained or installed, they can fail and lead to erosion problems.
Some common symptoms of retaining wall erosion include cracks, bulges, or leaning in the wall, as well as visible soil erosion or washout at the base of the wall. Solutions can include improving drainage, reinforcing the wall, or in some cases, rebuilding the wall entirely. In many cases, it's best to call in a professional landscaper or contractor to assess the issue and recommend the best course of action.