Weirs - Revision history

Mpollei@gfnet.com at 18:45, 21 July 2023

2023-07-21T18:45:12Z

@@ Line 1: / Line 1: @@
 __NOTOC__
 [[Category:Seepage Surveillance and Monitoring]]
 :“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) | EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>

Grichards at 23:06, 26 January 2023

2023-01-26T23:06:07Z

← Older revision		Revision as of 23:06, 26 January 2023
Line 3:		Line 3:
	:“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) \| EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>		:“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) \| EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>

	:~~“Sharp~~-crested weirs are simple open channel structures well suited to measuring the range of seepage and drainage discharge from most embankments. The discharge is a function of head, determined by measuring the water level in a stilling basin on the upstream side of the weir notch. The head is equal to the difference between the water surface elevation at that stilling basin and the lowest point along the weir crest. The notch is a standardized shape cut into a metal plate or other material capable of sustaining a sharp edge… Selection of a notch shape for a weir is a trade-off between the capacity and accuracy afforded by V-, rectangular-, and trapezoidal-notch weirs… V-notch weirs are typically used for low flow, are very accurate for low flows less than 1 cubic foot per second (cfs) and are reasonably accurate for flows as great as 10 cfs. Rectangular-notch weirs can accurately measure greater flows than a V-notch weir, and a minimum crest width of one foot is recommended. Trapezoidal-notch weirs are used for greater flows but have a lower accuracy than V or rectangular notches”.<ref name="EM 1110-2-1908" />		:“[[Sharp-Crested Weirs\|Sharp-crested weirs]] are simple open channel structures well suited to measuring the range of seepage and drainage discharge from most embankments. The discharge is a function of head, determined by measuring the water level in a stilling basin on the upstream side of the weir notch. The head is equal to the difference between the water surface elevation at that stilling basin and the lowest point along the weir crest. The notch is a standardized shape cut into a metal plate or other material capable of sustaining a sharp edge… Selection of a notch shape for a weir is a trade-off between the capacity and accuracy afforded by V-, rectangular-, and trapezoidal-notch weirs… V-notch weirs are typically used for low flow, are very accurate for low flows less than 1 cubic foot per second (cfs) and are reasonably accurate for flows as great as 10 cfs. Rectangular-notch weirs can accurately measure greater flows than a V-notch weir, and a minimum crest width of one foot is recommended. Trapezoidal-notch weirs are used for greater flows but have a lower accuracy than V or rectangular notches”.<ref name="EM 1110-2-1908" />

	:“Due to the difficulty of predicting seepage rate, weirs sometimes prove too small or too large for the flows encountered. However, weirs should first be sized for the expected range of flow and then modified if ill-suited to the encountered flows. Poorly sized weirs are inaccurate due to undesirable nappe formation, faulty head measurement, or submergence”.<ref name="EM 1110-2-1908" />		:“Due to the difficulty of predicting seepage rate, weirs sometimes prove too small or too large for the flows encountered. However, weirs should first be sized for the expected range of flow and then modified if ill-suited to the encountered flows. Poorly sized weirs are inaccurate due to undesirable nappe formation, faulty head measurement, or submergence”.<ref name="EM 1110-2-1908" />

			==Best Practices Resources==
			{{Document Icon}} [[Water Measurement Manual\| Water Measurement Manual (Reclamation)]]

	<!-- Revision history information -->		<!-- Revision history information -->
	{{revhistinf}}		{{revhistinf}}

Grichards at 00:10, 6 December 2022

2022-12-06T00:10:27Z

← Older revision		Revision as of 00:10, 6 December 2022
Line 3:		Line 3:
	:“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) \| EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>		:“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) \| EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>

	:“Sharp-crested weirs are simple open channel structures well suited to measuring the range of seepage and drainage discharge from most embankments. The discharge is a function of head, determined by measuring the water level in a stilling basin on the upstream side of the weir notch. The head is equal to the difference between the water surface elevation at that stilling basin and the lowest point along the weir crest. The notch is a standardized shape cut into a metal plate or other material capable of sustaining a sharp edge… Selection of a notch shape for a weir is a trade-off between the capacity and accuracy afforded by V-, rectangular-, and trapezoidal-notch weirs… V-notch weirs are typically used for low flow, are very accurate for low flows less than 1 cubic foot per second (cfs~~) (0.0283 cubic meters per second~~) and are reasonably accurate for flows as great as 10 cfs ~~(0.283 cubic meters per second)~~. Rectangular-notch weirs can accurately measure greater flows than a V-notch weir, and a minimum crest width of on foot ~~(30.5 cm)~~ is recommended. Trapezoidal-notch weirs are used for greater flows but have a lower accuracy than V or rectangular notches”.<ref name="EM 1110-2-1908" />		:“Sharp-crested weirs are simple open channel structures well suited to measuring the range of seepage and drainage discharge from most embankments. The discharge is a function of head, determined by measuring the water level in a stilling basin on the upstream side of the weir notch. The head is equal to the difference between the water surface elevation at that stilling basin and the lowest point along the weir crest. The notch is a standardized shape cut into a metal plate or other material capable of sustaining a sharp edge… Selection of a notch shape for a weir is a trade-off between the capacity and accuracy afforded by V-, rectangular-, and trapezoidal-notch weirs… V-notch weirs are typically used for low flow, are very accurate for low flows less than 1 cubic foot per second (cfs) and are reasonably accurate for flows as great as 10 cfs. Rectangular-notch weirs can accurately measure greater flows than a V-notch weir, and a minimum crest width of one foot is recommended. Trapezoidal-notch weirs are used for greater flows but have a lower accuracy than V or rectangular notches”.<ref name="EM 1110-2-1908" />

	:“Due to the difficulty of predicting seepage rate, weirs sometimes prove too small or too large for the flows encountered. However, weirs should first be sized for the expected range of flow and then modified if ill-suited to the encountered flows. Poorly sized weirs are inaccurate due to undesirable nappe formation, ~~fault~~ head measurement, or submergence”.<ref name="EM 1110-2-1908" />		:“Due to the difficulty of predicting seepage rate, weirs sometimes prove too small or too large for the flows encountered. However, weirs should first be sized for the expected range of flow and then modified if ill-suited to the encountered flows. Poorly sized weirs are inaccurate due to undesirable nappe formation, faulty head measurement, or submergence”.<ref name="EM 1110-2-1908" />

	<!-- Revision history information -->		<!-- Revision history information -->
	{{revhistinf}}		{{revhistinf}}

Grichards: Created page with "NOTOC Category:Seepage Surveillance and Monitoring :“Weirs are preferred to flumes for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necess..."

2022-12-05T23:37:33Z

Created page with "__NOTOC__ Category:Seepage Surveillance and Monitoring :“Weirs are preferred to flumes for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necess..."

New page

__NOTOC__
[[Category:Seepage Surveillance and Monitoring]]
:“Weirs are preferred to [[flumes]] for measuring flow in small open channels at embankments because a weir traps sediment and debris possibly produced by internal erosion, increasing the likelihood the sediment is noticed. However, the open channel conveying the seepage must have enough vertical drop for a weir. If the channel grade does not allow the weir to function as an unsubmerged weir, a flume may be necessary instead”.<ref name="EM 1110-2-1908">[[Instrumentation of Embankment Dams and Levees (EM 1110-2-1908) | EM 1110-2-1908 Instrumentation of Embankment Dams and Levees, USACE, 2020]]</ref>

:“Sharp-crested weirs are simple open channel structures well suited to measuring the range of seepage and drainage discharge from most embankments. The discharge is a function of head, determined by measuring the water level in a stilling basin on the upstream side of the weir notch. The head is equal to the difference between the water surface elevation at that stilling basin and the lowest point along the weir crest. The notch is a standardized shape cut into a metal plate or other material capable of sustaining a sharp edge… Selection of a notch shape for a weir is a trade-off between the capacity and accuracy afforded by V-, rectangular-, and trapezoidal-notch weirs… V-notch weirs are typically used for low flow, are very accurate for low flows less than 1 cubic foot per second (cfs) (0.0283 cubic meters per second) and are reasonably accurate for flows as great as 10 cfs (0.283 cubic meters per second). Rectangular-notch weirs can accurately measure greater flows than a V-notch weir, and a minimum crest width of on foot (30.5 cm) is recommended. Trapezoidal-notch weirs are used for greater flows but have a lower accuracy than V or rectangular notches”.<ref name="EM 1110-2-1908" />

:“Due to the difficulty of predicting seepage rate, weirs sometimes prove too small or too large for the flows encountered. However, weirs should first be sized for the expected range of flow and then modified if ill-suited to the encountered flows. Poorly sized weirs are inaccurate due to undesirable nappe formation, fault head measurement, or submergence”.<ref name="EM 1110-2-1908" />


{{revhistinf}}