60 foot tall pine has a 4-6 inch root traversing my stream. The water will not flow over the root (too high) and going under the root will also cause problems. Is it safe to cut the root? Perhaps drill some holes thru it to let the water flow through it?
It depends on the size of the pine- how much root system it has. Here in the "piney woods" the typical southern pines have 4 ' diameter trunks and could easily lose a 6 " root with no problem. When the center of my lot was cleared of pines , a bulldozer dug out one side then pushed over the trees ( not quite as easy as it sounds). The idea was that the roots were exposed and there was no stump in the ground. So I saw many root balls of 2.5 to 4.5 ft. diameter trees . A 6 " root would been a very small amount of the total ; and the biggest root mass went straight down.