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What is the significance of tailwater level in culverts?

The headwater level and tailwater level of culverts are important parameters in hydraulic design. The headwater level cannot be set too large, otherwise flooding upstream may occur leading to the loss of life and properties. On the other hand, the tailwater level of culverts has to comply with the following requirements:

(i) For low tailwater levels at the outlet of culverts, the small depths of flow may cause significant erosion of downstream channels.

(ii) For high tailwater levels, it may cause the culvert upstream to be flowing full or even under submerged condition. As such, the headwater level is increased in order to flow through the culvert and this in turnincreases the flooding risk associated with high headwater level.

Tailwater level in culvert.


This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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3 comments on "What is the significance of tailwater level in culverts?"

Yih says:

How do you calculate your tailwater for the outlet control of RCP pipe culvert design under free flow conditions ?

Do you need rating curve?

or you just assume that the 1200X900 RCBC meaning tailwater assumed is 900?

Carolyn C. Cottrell says:

Thank you for sharing this informative article on the crucial role of headwater and tailwater levels in hydraulic design. It’s evident that maintaining a delicate balance between these parameters is essential to prevent potential flooding and erosion issues. Your article effectively highlights the potential consequences of setting the headwater level too large or the tailwater level too low or high. This underscores the significance of accurate and thoughtful hydraulic design to ensure the safety of communities and the protection of valuable properties. The insights provided in your article serve as a valuable reminder of the intricate considerations that engineers and designers must take into account when dealing with culvert systems.

Martin Finch says:

Thank you for your time and knowledge of the subject. I have been a practicing engineer for 15 years and I finally have a grasp on the subject and role it plays during the design of stormwater culverts and/or stormwater control measures. Thanks again.

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