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The broad crested weir at the Thorp grist mill in Thorp, Washington, US. Commonly, weirs are used to prevent flooding, measure water discharge, and help render rivers more navigable by boat. In some locations, the terms dam and weir are synonymous, but normally there is a clear distinction made between the structures. Usually, a dam is designed ...
A drop structure, also known as a grade control, sill, or weir, is a manmade structure, typically small and built on minor streams, or as part of a dam's spillway, to pass water to a lower elevation while controlling the energy and velocity of the water as it passes over.
Roller dams are a type of weir, or a dam that is designed to allow water to flow over the top in continuous action. They are used on rivers or other such moving bodies of water where erosion damage is undesirable, yet likely to occur. A short wall, lip, or parabolic channel is constructed on the downstream side of the dam parallel to the dam face.
Mill ponds were often created through the construction of a mill dam or weir (and mill stream) across a waterway. In many places, the common proper name Mill Pond has remained even though the mill has long since gone. It may be fed by a man-made stream, [3] known by several terms including leat and mill stream.
Weir on Lake Tecumseh, Virginia. A flow control structure is a device that alters the flow of water in a stream, drainage channel or pipe. As a group these are passive structures since they operate without intervention under different amounts of water flow and their impact changes based on the quantity of water available.
In hydraulic engineering, a nappe is a sheet or curtain of water that flows over a weir or dam. The upper and lower water surface have well-defined characteristics that are created by the crest of a dam or weir. [1] Both structures have different features that characterize how a nappe might flow through or over impervious concrete structures. [2]
The largest dam removal project in U.S. history has freed the Klamath River, inspiring hope among Indigenous activists who pushed for rewilding to help save salmon.
In the United States, each state defines what constitutes a non-jurisdictional dam. In the state of Colorado a non-jurisdictional dam is defined as a dam creating a reservoir with a capacity of 100 acre-feet or less and a surface area of 20 acres or less and with a height measured as defined in Rules 4.2.5.1. and 4.2.19 of 10 feet or less. [ 60 ]