Swale guidance

Background: Just purchased a new home in February. The garage floor was constantly damp and you could smell moisture. The previous owner had the grade going all the way up to the 3rd row of brick, which is not good esp since the grade of the yard goes towards the garage. I decided to dig a swale where I was going to put perforated pipe at the bottom and cover with stone, but how do I keep the sides (or slope) from eroding my swale? Or am I even doing this correctly?