I have a commercial customer that long story short needs to keep this grass area free from excess water. The depth of this bed is only like 8-12". It sits on top of a parking garage, but also shares a wall with the basement offices. During excessive rain, or when this fountain overflows, this grass area recieves too much water, and ends up flooding the basement offices. she had a proposal to do an 8" tall oklahoma flag chop wall, as to divert the water away from the grass and onto the sidewalk. i dont have much faith that the wall bordering the grass is going to be an effective-long term barrier for water. my vote is to install 2-3 seperate french drains and just suck all the water out of this area. It has positive drainage to drain down hill, but then again its only 8"-12" deep. She had a quote for 85' linear ft of 8" tall wall. I figure 2 tons of chopped flagstone, but I don't think the bidding contractor was planning on pouring a footer... thoughts? what can my customers options be?