I have done that quite a bit, and have learned a few tricks to help spead it up. If you can find a 10' - 15' tall sycamore, they make great brushpiles, and the sycamore will sink by itself, it does not require cinder blocks. If you are taking it to a cove or area away from any current, they will sink and usually stay in that area until they rot away in a few years.