# Water flow thru 18" corrugated culvert

• John1397
In summary, the conversation involves a formula that the speaker is having trouble figuring out. The variables H, Q, L, D, and A are defined, and the speaker mentions that they have no clue what g represents. They also mention the dimensions and water levels of a culvert. The speaker advises against using this formula for actual culvert calculations and provides a link to a document with the correct procedure. They also mention that one of the nomograms may give incorrect answers for corrugated steel pipe culverts and suggest an alternative method for determining flow rate.
John1397
Attached formula can't figure out. H is 12 inches, Q is what I want to know, L is 40 feet, D is 18 inches, A I assume is area of 18 inches, g have no clue what this is. The Culver is 18" X 40 foot long coragated with water 1 foot over inlet and water on outlet 2" lower than culvert and the culverts tail is 2 inches lower than head. end

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Q=discharge in cubic feet per second.
D=diameter of pipe in feet. 18" = 3/2 feet, radius = 3/4 ft.
A=cross-sectional area of pipe in square feet. = Pi * 9/16 sq ft.
L=length of culvert in feet. = 40 ft.
H=head on pipe in feet or the difference in the water level at the two ends. = (12+2+2)/12 ft.
g=acceleration of gravity. = 32 ? ft/s²

What is the problem?

If you are using this for an actual culvert, do not be surprised if the calculation seems to give a wrong answer. The correct procedure for calculating culvert flow is in a document titled HDS5 - Hydraulic Design of Highway Culverts, 3rd Edition. It's from the U.S. Department of Transportation, Federal Highway Administration. Here's a link: https://www.fhwa.dot.gov/engineering/hydraulics/pubs/12026/hif12026.pdf.

Be advised that at least one of the nomograms gives wrong answers for corrugated steel pipe culverts. The equations are correct. Note that one single equation cannot cover all cases of headwater level, tailwater level, entrance conditions, culvert slope, culvert length, approach velocity and direction, downstream channel velocity, inlet control vs outlet control, etc.

If you just want to know the flow rate of a nearby culvert, you could measure the flow cross sectional area and culvert length, then throw a stick in and measure the time to flow through. Velocity times area equals flow.

berkeman and anorlunda

## 1. What is the purpose of a corrugated culvert?

A corrugated culvert is used to allow water to flow through a roadway or other structure, preventing flooding and erosion. It can also be used to divert water away from buildings or other areas.

## 2. How does water flow through an 18" corrugated culvert?

Water flows through an 18" corrugated culvert due to gravity and the slope of the land. The corrugated design of the culvert allows for smooth flow and prevents clogging.

## 3. What factors affect the flow of water through an 18" corrugated culvert?

The flow of water through an 18" corrugated culvert can be affected by the slope of the land, the amount of water present, and any obstructions or debris in the culvert.

## 4. How is the capacity of an 18" corrugated culvert determined?

The capacity of an 18" corrugated culvert is determined by its size, shape, and slope. Other factors such as the type of material used and the condition of the culvert can also affect its capacity.

## 5. What maintenance is required for an 18" corrugated culvert?

To ensure proper water flow, an 18" corrugated culvert should be regularly inspected for any damage or obstructions. It may also need to be cleaned out periodically to prevent clogging. In some cases, repairs or replacements may be necessary.

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