Moss Rock Preserve is drained by a small stream known as Hurricane Branch. This stream begins in the preserve, but where it begins flowing changes seasonally. During the fall, the upper branch may be dry, but during the wet months of late winter and early spring most of the branch will be flowing. Hurricane Branch joins Patton Creek, which then joins the Cahaba River. As part of the Mobile River Basin, the waters of the Cahaba eventually enter Mobile Bay.