Head of navigation

Head of navigation is the farthest point above the mouth of a river that can be navigated by ships. Determining the head of navigation can be subjective on many streams, as this point may vary greatly with the size of the ship being contemplated for navigation and the seasonal water level. On others, it is quite objective, being caused by a waterfall or a dam without navigation locks. Several rivers in a region may have their heads of navigation along a line called the Fall line.