Headwater: 2" drop in a 40 foot length culvert

• Misc.
• John1397
In summary, the flow through a culvert under inlet control is very small, while the flow through a culvert under outlet control or in the transition region is much larger.
John1397
TL;DR Summary
I am trying to figure out the fps of 18 inch culvert with 13.5 inches water over the top on inlet and about 2 inches lower on the outlet and 2 inch drop on the outlet end over 40 foot length, what I need to know what would be the headwater on this type of configuration?

Attachments

• IMG_20220828_185350.jpg
34.2 KB · Views: 108
John1397 said:

I am trying to figure out the fps of 18 inch culvert with 13.5 inches water over the top on inlet and about 2 inches lower on the outlet and 2 inch drop on the outlet end over 40 foot length, what I need to know what would be the headwater on this type of configuration?
Sorry, what is the "fps" that you are asking about? Are you asking what the flow rate would be for a water channel that has a drop of 2" over a 40 foot length? If so, the answer is very small -- hopefully you are not trying to generate any useful energy out of this flow...

It sounds like you want to calculate the flow through a culvert, given some dimensions and depths. There is no one equation to calculate this. There is a procedure that takes into account the culvert dimensions, culvert shape (round vs arch bottom), roughness (CSP vs concrete vs plastic vs ...), length, slope, headwater level, tailwater level, water approach velocity and direction, tailwater velocity, entrance configuration, etc. That procedure starts by determining whether the flow is under inlet control, outlet control, or in the transition region between. Here is a link to the standard reference, HDS5 Hydraulic Design of Highway Culverts, 3rd Edition: https://www.fhwa.dot.gov/engineering/hydraulics/pubs/12026/hif12026.pdf.

Be advised that at least one of the nomograms is in error by more than an order of magnitude, so use the equations.

BillTre and berkeman
Seen that throwing stick in water time how many seconds from into out works to.

1. What is the purpose of a culvert?

A culvert is a structure that is designed to allow water to flow under a road, railway, or other obstruction. It helps to prevent flooding and erosion by directing the water to a designated outlet.

2. How does the length of a culvert affect its performance?

The length of a culvert plays a crucial role in its performance. A longer culvert can handle more water flow, but it also increases the potential for clogging and maintenance issues. A shorter culvert may be more efficient, but it may not be able to handle large volumes of water.

3. What factors determine the size of a culvert?

The size of a culvert is determined by the expected water flow, the topography of the area, and the materials used to construct the culvert. Other factors such as the surrounding land use and potential for debris buildup should also be considered.

4. How does the drop in a culvert affect the water flow?

The drop in a culvert, also known as the slope or gradient, affects the speed and volume of water flow. A steeper drop will result in faster water flow, while a gentler slope will slow down the water. It is important to consider the drop when designing a culvert to ensure proper water flow and prevent erosion.

5. What is the recommended drop for a culvert?

The recommended drop for a culvert varies depending on the specific project and location. In general, a drop of 1% to 5% is recommended for culverts to prevent clogging and maintain proper water flow. It is important to consult with a professional engineer to determine the best drop for a specific culvert design.

• Mechanical Engineering
Replies
2
Views
2K
• DIY Projects
Replies
2
Views
2K
• Other Physics Topics
Replies
30
Views
951
• Mechanics
Replies
3
Views
1K
• General Engineering
Replies
10
Views
790
• Mechanical Engineering
Replies
6
Views
977
• Electrical Engineering
Replies
38
Views
3K
• DIY Projects
Replies
21
Views
5K
• Mechanical Engineering
Replies
3
Views
901
• Mechanics
Replies
10
Views
4K