When it rains, the lower right part of my driveway slab (12x20) floods with about 2-3 inches of water. The problem is that to the right of my driveway is some rock landscaping and then my yard and to the left is an alley. I'm not sure if I can reroute the water or if it would be easier to pour concrete over the low end. I am just concerned that adding two inches of new concrete to old concrete will eventually chip away, especially since I will be needing to fan the new concrete out as the grade gets higher. Suggestions?