Weir in Doe River Are We EarthCache
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SO what is a Weir Dam you may be asking. Well it is also known as a lowhead dam, is a small overflow-type dam commonly used to raise the level of a river or stream. Weirs have traditionally been used to create mill ponds in such places.
The weir is made significantly longer than the width of the river by forming it in a 'U' shape or running it diagonally, instead of the short perpendicular path. Since the weir is the portion where water is overflowing, a long weir allows a lot more water with a small increase in overflow depth. This is done in order to minimize fluctuation in the depth of the river upstream with changes in the flow rate of the river.
Weirs allow hydrologists and engineers a simple method of measuring the rate of fluid flow in small to medium-sized streams, or in industrial discharge locations. Since the geometry of the top of the weir is known, and all water flows over the weir, the depth of water behind the weir can be converted to a rate of flow. Because a weir will typically increase the oxygen content of the water as it passes over the crest, a weir can have a detrimental effect on the local ecology of a river system. A weir will artificially reduce the upstream water velocity, which can lead to an increase in siltation. The weir may pose a barrier to migrating fish. Fish ladders provide a way for fish to get between the water levels.
Types of Dams:
There are different types of weir. It may be a simple metal plate with a V-notch cut into it, or it may be a concrete and steel structure across the bed of a river. A weir which causes a large change of water level behind it, compared to the error inherent in the depth measurement method, will give an accurate indication of the flow rate.
Broad crested weir (or broad-crested weir)
Sharp crested weir
Crump weir (named after the designer)
Needle dam
Proportional weir
Combination weir
MF weir
V-notch weir
Rectangular weir
Cipolletti (trapezoidal) weir
Labyrinth weir
Tidal weir
Long crested weir - e.g. Duckbill and diagonal.
Broad-crested weir:
When the crest is “broad”, the streamlines become parallel to the crest invert and the pressure distribution above the crest is hydrostatic.
Sharp crested weir:
A sharp-crested weir allows the water to fall cleanly away from the weir. Sharp crested weirs are typically 1/4" or thinner metal plates.
Combination weir:
The sharp crested weirs can be considered into three groups according to the geometry of weir: a) the rectangular weir, b) the V or triangular notch and c) special notches, such as trapezoidal, circular or parabolic weirs.
V-notch weir:
The V-notch weir is a triangular channel section, used to measure small discharge values. The upper edge of the section is always above the water level, and so the channel is always triangular simplifying calculation of the cross-sectional area.
The Unaka Range is a mountain range on the border of Tennessee and North Carolina, in the southeastern United States. It is a subrange of the Appalachian Mountains and is part of the Blue Ridge Mountains physiographic province. The Unakas stretch approximately from the Nolichucky River to the south to the Watauga River to the north. The Unakas include the prominent Roan Highlands, where several summits rise above 6,000 feet. The Iron Mountains border the Unakas to the north, and the Bald Mountains border the Unakas opposite the Nolichucky to the south.
DEFINITION OF A WATERSHED. A watershed is defined as the geographic land area which drains to a common outlet, such as a point on a larger stream, lake, underlying aquifer, estuary, wetland, or ocean.
The Watauga River Watershed includes cool, clear streams with high gradient and rugged terrain. It contains one of the richest centers of biodiversity in the eastern U.S.
Springs and caves are relatively numerous in the Southern Limestone/Dolomite Valleys and Low Rolling Hills. The watershed has great aquatic habitat diversity and supports a
diverse fish fauna.
The Tennessee portion of Watauga River Watershed is located in East Tennessee and includes parts of Carter, Johnson, Sullivan, Unicoi, and Washington Counties.
General Location of the Watauga River Watershed.
COUNTY % OF WATERSHED IN EACH COUNTY
Carter 54.3
Johnson 25.7
Washington 14.2
Sullivan 2.9
Unicoi 2.9
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To get credit for this earthcache you need to do the following:
1.) Take a photo of you and your gps with the dam behind you
2.) Using the information above email the answer to this: Which type of weir dam is this?
3.) Using a small floating object place it in the water at the cover bridge and then using a watch tell me how fast (flow rate) your object is moving from the covered bridge to the weir dam?
4.) What is the color is the water before it goes over the dam and after and explain why the color is different.
Additional Hints
(Decrypt)
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