Few tree species will thrive and many will die in such a situation. A technique sometimes used to reduce the perched water table effect when increasing grade with relatively fine textured fill is to create a gradual boundary or transition zone between the original soil and the fill. This is done by applying two inches of fine-textured fill to the existing soil and rototilling it in to a depth of four to six inches. Apply a second two inches of fine-textured soil and rototill it in to a depth of four to six inches. Then apply the remaining fill to bring the area up to the desired grade.
Minor fills add no more than four inches of fill.
Create a transition zone as shown if soil textures vary. Just as with decreasing soil grade, increasing soil grade can channel increased amounts of surface and subsurface water into areas where trees are growing or are to be planted. The results and concerns are the same. If increased water is channeled into areas where trees are to be planted, choice of species will be limited to trees tolerant of the new, wetter conditions. As noted earlier, the best solution to changes in grade that markedly alter water distribution on a property is to anticipate problems that might be created and modify the grading plan to minimize the impacts.