Editing Head of navigation

{{Short description|Farthest navigable point up a waterway}}
{{refimprove|date=May 2023}}

The '''head of navigation''' is the farthest point above the [[river mouth|mouth of a river]] that can be navigated by [[ships]].<ref>Jason King, "[https://www.hiddenhydrology.org/bring-me-the-head-of-navigation/ Bring Me the Head of Navigation]", Hidden Hydrology, Oct. 27, 2018; accessed 2023.05.15.</ref>  Determining the head of navigation can be subjective on many streams, as the point may vary greatly with the size or the [[draft (hull)|draft]] of the ship being contemplated for navigation and the seasonal water level. On others, it is quite objective, being caused by a [[waterfall]], a low bridge that is not a [[drawbridge]], or a [[dam]] without navigation [[canal lock|locks]]. Several rivers in a region may have their heads of navigation along a line called the [[fall line]]. 

Longer rivers such as the [[River Thames]] may have several heads of navigation depending on the size of the vessel. In the case of the Thames, that includes [[London Bridge]], which historically served as the head of navigation for tall ships; [[Osney Bridge]] in [[Oxford]], which has the lowest headroom of any bridge on the Thames that generally restricts navigation to smaller vessels such as [[narrowboat]]s and [[cabin cruiser]]s, and the long reach above [[St John's Lock]], the first lock downstream of the [[Thames Head|river’s source]], on the outskirts of [[Lechlade]], where the river can become treacherously narrow and shallow for anything but small motorboats and human-powered vessels.

In the [[United States]], the entirety of a navigable waterway up to the head of navigation is subject to federal jurisdiction.<ref>33 CFR § 329.7.</ref>  The government recognizes that the "upper limit" of navigability will "often be the same point traditionally recognized as the head of navigation" but may under some circumstances lie "yet farther upstream."<ref>33 CFR § 329.11(b).</ref>

==References==
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[[Category:Nautical terminology]]