navigation servitude

All navigable waters are under the control of the United States for the purpose of regulating and improving navigation, and although the title to the shore and submerged soil is in the various states and individual owners under them, it is always subject to the servitude in respect of navigation created in favor of the Federal government by the Constitution. ... acts done in the proper exercise of governmental powers, and not directly encroaching upon private property, though their consequences may impair its use, are universally held not to be a taking within the meaning of the constitutional provision.