A needle dam is a

weir A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...

designed to maintain the level or flow of a river through the use of thin "needles" of wood. The needles are leaned against a solid frame and are not intended to be water-tight. Individual needles can be added or removed by hand to constrict the flow of the river, forming a sluice. One early needle dam maintains the level of

Lake Lucerne __NOTOC__ Lake Lucerne (german: Vierwaldstättersee, literally "Lake of the four forested settlements" (in English usually translated as ''forest cantons''), french: lac des Quatre-Cantons, it, lago dei Quattro Cantoni) is a lake in central S ...

in Lucerne, Switzerland by restricting the flow of the Reuss, several are still in operation on the

Meuse The Meuse ( , , , ; wa, Moûze ) or Maas ( , ; li, Maos or ) is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea from the Rhine–Meuse–Scheldt delta. It has a t ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

and others were built in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

in the 19th century. The first needle dam in the United States was completed in 1896 on the Big Sandy River, downstream from the city of

Louisa, Kentucky Louisa is a home rule-class city located at the merger of the Levisa and Tug Forks into the Big Sandy River. It is located in Lawrence County, Kentucky, in the United States, and is the seat of its county. The population was 2,467 at the 2010 ...

. A similar approach, now known as

paddle and rymer weir A flash lock is a type of lock for river or canal transport. Early locks were designed with a single gate, known as a flash lock or staunch lock. The earliest European references to what were clearly flash locks were in Roman times. Developme ...

s, was used since medieval times on the

River Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the R ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

to create flash locks.

Notes

External links

Video and annotation on the Needle Dam at Lucerne on the river Reuss
Dams Weirs {{dam-stub