出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2013/11/13 20:21:47」(JST)
A body of water, such as a river, canal or lake, is navigable if it is deep, wide and slow enough for a vessel to pass. Preferably there are few obstructions such as rocks or trees to avoid. Bridges must have sufficient clearance. High water speed may make a channel unnavigable. Waters may be unnavigable because of ice, particularly in winter. Navigability depends on context: A small river may be navigable by smaller craft, such as a motor boat or a kayak, but unnavigable by a cruise ship. Shallow rivers may be made navigable by the installation of locks that increase and regulate water depth, or by dredging.
Inland Water Transport (IWT) Systems have been used for centuries in countries including India, China, Egypt, the Netherlands, the United States, Germany, China, and Bangladesh. In the Netherlands, IWT handles 46% of the nation's inland freight; 32% in Bangladesh, 14% in the United States, and 9% in China.
What constitutes 'navigable' waters can not be separated from the context in which the question is asked. Numerous federal agencies define navigable waters for various purposes from admiralty jurisdiction, to pollution control, to the licencing of dams, to property boundaries. The numerous definitions and jurisdictional statutes have created an array of case law specific to which context the question of navigability arises. Some of the most commonly discussed definitions are listed here.
Navigable waters, as defined by the US Army Corps of Engineers as codified under 33 CFR 329, are those waters that are subject to the ebb and flow of the tide, and those inland waters that are presently used, or have been used in the past, or may be susceptible for use to transport interstate or foreign commerce while the waterway is in its ordinary condition. Section 10 of the Rivers and Harbors Act of 1899 (33 U.S.C. 403), approved 3 March 1899, prohibits the unauthorized obstruction of a navigable water of the U.S. This statute also requires a permit from the U.S. Army Corps of Engineers for any construction in or over any navigable water, or the excavation or discharge of material into such water, or the accomplishment of any other work affecting the course, location, condition, or capacity of such waters.
The definition of Navigable waterways reviewed for purposes of title is first based upon Federal laws. If a river was considered navigable at the time of statehood, the land below the navigable water was conveyed to the state as part of the road system. Most states retained title to these navigable rivers (in trust) as highways in order to facilitate transport and commerce. Some states divested themselves of title to the land below navigable rivers, but under federal laws this dose not block the free passage of boats. Title to the lands submerged by smaller streams not navigable at the time of statehood, under ordinary conditions, for purposes of commerce are considered part of the property through which the water flows.
The scope of FERCs authority was granted under the Federal Power Act, 1941 (16 U.S.C 791). Such authority is based on congressional authority to regulate commerce; it is not based exclusively on title to the riverbed [16 U.S.C. 796(8)]. Therefore FERCs permitting authority extends to even non-navigable tributaries as recognized by the courts, [US v. Rio Grande Irrigation, 174 U.S. 690, 708 (1899)],[Oklahoma v. Atkinson, 313 US 508, 525].
Also, the Clean Water Act has introduced the terms "traditional navigable waters," and "waters of the United States" to define the scope of Federal jurisdiction under the Clean Water Act. Here, "Waters of the United States" include not only navigable waters, but also tributaries of navigable waters and nearby wetlands with "a significant nexus to navigable waters"; both are covered under the Clean Water Act. The Clean Water Act more expansive test for "traditional navigable waters" also include the capacity to accommodate recreational use of a water body,and removes that navigable capacity be defined by the 'ordinary condition' of the water. Because the Clean Water Act encompasses areas in excess of public property, the broader definitions of "navigable" and "significant nexus" used to establish the scope of authority under the CWA are still open to judicial interpretation as indicated in two U.S. Supreme Court decisions: "Carabell v. United States" and "Rapanos v. United States".[1]
In India there are currently three National Waterways totaling a distance of 2921 km. They are:
It is estimated that the total navigable length of inland waterways is 14500 km. A total of 16 million tonnes of freight is moved by this mode of transport.
Waterways provide enormous advantages as a mode of transport compared to land and air modes of transports.
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