flagstone swale construction
I have a drainage issue in my backyard that I have tried to correct by constructing a swale measuring 2' x 25'. I lined the swale with river rock but was told by a city stormwater manager that it would be better to use flagstone to maximize water flow. He suggested laying the flagstone on top of landscape fabric without mortar. Is this the best way? I would think pouring paver peebles or sand inbetween the flagstone would create a smoother surface area and allow for contraction/expansion.