I think Warren is saying that the swale itself could become a collector of water which would slowly seep into the area below.
I think it would make it worse because swales are usually built to encourage water to go into the ground. If the op had asked for ways for more water to get into the ground then I have no doubt that somebody here would have suggested a swale. To use a swale to take water away could be asking for trouble if the bottom of it is not completely waterproof.
If the water was not readily shedding off this could be an issue. I don't think it would make it worse, it would just not help the situation.
It's really quite simple. It's a path along the bottom of a slope. Rain runs down the slope, onto the path and then runs away along the path. Obviously the path would have to be built to just below ground level. If you don't want a path then that's fair enough.
Warren...I can't really visualize exactly what you mean but i dont really like the idea of actual paving down the side of my house. I think i may be misunderstanding you though.
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