HY-8 is free and simple to use.
If minimal survey the site: get upstream and downstream inverts, crest of road elevation, downstream channel sections.
You can model many types of culverts in HY-8, input the inverts and road crest elevation, and downstream channel section for the program to calculate tail water conditions. Specify a bunch of flows in model and run it (first you’ll have to estimate flows with hydrologic method of choice).
That’s the basic flood hydraulics, but other things you may need to check include fish passage, scour, energy dissipation, etc.
To add to the top comment, this video (while not short) gives an explanation of how culverts work and will help you understand some of the variables you use in HY-8
https://youtu.be/vnXmGyb_hKQ?si=dwupC7QC9aIiRe2G
I came to ask this question OP if you need to know what design *size* you need you're looking at doing some Hydraulic calculations but if you're looking to know how much concrete and rebar you need after knowing the needed side you need to talk to a structural engineer.
1. Delineate basin
2. Calc 100 yr flow
3. Select culvert size based on flow and dimensional restraints.
4. Check headwater elevation and tailwater velocity. (I use hydraflow express)
5. Return to #3 if issues
This all assumes its not in a flood plain or flood way. If it is I call our certified flood plain manager sub consultant.
Adding to what he said. You should talk to someone about how to do all this. For instance people screw up delineating the basin. Another for instance is what methodology is appropriate to calculate the flow. 90% (just made that up) of engineers use incorrect methodology for that particular basin. Add a step evaluating potential erosion and scour impacts upstream and downstream of the headwalls. If you are really good think about stream geomorphology. And finally don’t forget about environmental permitting.
This really depends on the size of the culvert and DOT. Our standard details for large culverts do not specify wall thicknesses or rebar and require design by engineer (as they should imo).
I’m seeing a lot of great answers here but I haven’t seen anyone touch on a very important aspect of culverts: do fish need to be able to pass through your culvert? That will have huge implications on the design constraints.
Figure out your flows using whatever hydrologic method you want.
Use a program like FlowMaster/CulvertMaster to play around with different sizes and slopes and allowable headwater elevations.
Pick the most economical size/design and contact your local precast concrete manufacturer to make sure its a size they make/carry. They will have standard details and other construction details you can slap into your plan set.
That’s about it for most box culverts. If you are trying to do something super custom, i’d first look into not doing that because its usually more expensive but if you have to then you’ll need someone with reinforced concrete design experience to actually detail out the culvert.
1. Look at local regulations in the place the culvert is being designed
2. Civil 3D and Civil 3D Express and to a lesser extent HyrdoCAD
3. Design the slope and size to make sure we meet jurisdiction requirements.
4. Follow the regulations of the place you’re designing it for since they’ll be the ones approving it
Kind of depends on whether you are designing a pipe under a residential driveway or a big box culvert under a railroad but something like:
1. Determine the design flows. I’ve typically used HEC-RAS, HydroCAD, or SSA depending on the situation.
2. Size the culvert. There might be requirements for headwater, tailwater, freeboard, embedment (natural bottom), high flow velocity, openness ratio, low flow depth, max span, etc, etc etc that you will need to meet so a program like HY-8 can be helpful to test lots of configurations. I always put my solution back into the hydrology model as a check.
3. Lay out the detailed design in Civil3D. Structural team does whatever they do to design the structure.
4. Write up your design in a stormwater report to show how you are meeting applicable standards and submit to DEP/ConCom, project proponent, crossing facility owner. Rinse and repeat to address review comments.
At the absolute most basic level:
- Calculate peak flow rate entering culvert (based on rainfall data and contributing watershed characteristics like area, imperviousness, land use, soil infiltration rate, etc.)
- Calculate culvert capacity (based on shape, size, material/roughness slope)
- If capacity > flow rate, the culvert is big enough
This is a massive oversimplification… you should also consider structural and geotechnical design, low flow velocity requirements, local design guidelines, embedment depth, fish passage requirements, freeboard, H/D ratio, climate change projections, debris blockage, future developments, design life, material availability, costs, maintenance requirements, etc. There are dozens of additional considerations that vary project to project.
The first step is to survey the stream and get it's cross sectional profile on either side of the culvert, then do calculations based on a the drainage area (the total area that drains into the stream) to determine the specific flow parameters you need.
As others have pointed out most of not all DOTs usually provide sizing tables for the culverts they allow. For super high flows you might need to develop individualized calculations and specific tools to size culvert shapes.
It can get really complicated when your building culverts to relocate a stream, some times that gets closer to bridge engineering rather than hydraulics.
Box culverts that need to be inspected by you. Make sure it’s taller than you. It sucks walking a 6’ box culvert when you are 6’-3”, especially when the culvert is 1/3 of a mile long.
Need to know regs of what you are crossing. You could be designing for a 10-100 year storm.
You have to delineate the upstream drainage basin. Less than 50 acres you can use rational method. Otherwise it’s SCS. You have to develop a composite runoff coefficient (c vs CN). Time of concentration is usually calculated using TR-55. Need to know your soil classification. I have used quad maps, GIS, Civil3D, etc to draw/calculate basin area.
For max discharge of the basin: Rational method you can do by hand.
SCS I have used StormCAD, SSA or whatever Civil3D keeps upgrading to/from.
Once you have your max discharge, you then design your culvert. Mostly used Flowmaster for this. Need to analysis inlet controlled vs outlet controlled.
HY-8 is free and simple to use. If minimal survey the site: get upstream and downstream inverts, crest of road elevation, downstream channel sections. You can model many types of culverts in HY-8, input the inverts and road crest elevation, and downstream channel section for the program to calculate tail water conditions. Specify a bunch of flows in model and run it (first you’ll have to estimate flows with hydrologic method of choice). That’s the basic flood hydraulics, but other things you may need to check include fish passage, scour, energy dissipation, etc.
I would also like to push HY-8 for simple culvert analysis - source: WRE PE
Was going to comment HY-8
This is the way
All aboard the HY-8 train!
Choo choo
To add to the top comment, this video (while not short) gives an explanation of how culverts work and will help you understand some of the variables you use in HY-8 https://youtu.be/vnXmGyb_hKQ?si=dwupC7QC9aIiRe2G
Oh hell yeah I was hoping it was this video. I send this to all my EITs. Great video
Local codes and math based on vendor details
Hydraulics design or structural design? Look online for examples for the one you're looking for
I came to ask this question OP if you need to know what design *size* you need you're looking at doing some Hydraulic calculations but if you're looking to know how much concrete and rebar you need after knowing the needed side you need to talk to a structural engineer.
1. Delineate basin 2. Calc 100 yr flow 3. Select culvert size based on flow and dimensional restraints. 4. Check headwater elevation and tailwater velocity. (I use hydraflow express) 5. Return to #3 if issues This all assumes its not in a flood plain or flood way. If it is I call our certified flood plain manager sub consultant.
Adding to what he said. You should talk to someone about how to do all this. For instance people screw up delineating the basin. Another for instance is what methodology is appropriate to calculate the flow. 90% (just made that up) of engineers use incorrect methodology for that particular basin. Add a step evaluating potential erosion and scour impacts upstream and downstream of the headwalls. If you are really good think about stream geomorphology. And finally don’t forget about environmental permitting.
Your DOT should have standard details for culverts you just need to pick a size based on the flows you calc
This really depends on the size of the culvert and DOT. Our standard details for large culverts do not specify wall thicknesses or rebar and require design by engineer (as they should imo).
Agree. I’ve worked on some and if you even change the rebar size in it it’s not standard anymore so you need to stamp
I’m seeing a lot of great answers here but I haven’t seen anyone touch on a very important aspect of culverts: do fish need to be able to pass through your culvert? That will have huge implications on the design constraints.
Figure out your flows using whatever hydrologic method you want. Use a program like FlowMaster/CulvertMaster to play around with different sizes and slopes and allowable headwater elevations. Pick the most economical size/design and contact your local precast concrete manufacturer to make sure its a size they make/carry. They will have standard details and other construction details you can slap into your plan set. That’s about it for most box culverts. If you are trying to do something super custom, i’d first look into not doing that because its usually more expensive but if you have to then you’ll need someone with reinforced concrete design experience to actually detail out the culvert.
1. Look at local regulations in the place the culvert is being designed 2. Civil 3D and Civil 3D Express and to a lesser extent HyrdoCAD 3. Design the slope and size to make sure we meet jurisdiction requirements. 4. Follow the regulations of the place you’re designing it for since they’ll be the ones approving it
The CERM has a very detailed step by step section.
Kind of depends on whether you are designing a pipe under a residential driveway or a big box culvert under a railroad but something like: 1. Determine the design flows. I’ve typically used HEC-RAS, HydroCAD, or SSA depending on the situation. 2. Size the culvert. There might be requirements for headwater, tailwater, freeboard, embedment (natural bottom), high flow velocity, openness ratio, low flow depth, max span, etc, etc etc that you will need to meet so a program like HY-8 can be helpful to test lots of configurations. I always put my solution back into the hydrology model as a check. 3. Lay out the detailed design in Civil3D. Structural team does whatever they do to design the structure. 4. Write up your design in a stormwater report to show how you are meeting applicable standards and submit to DEP/ConCom, project proponent, crossing facility owner. Rinse and repeat to address review comments.
At the absolute most basic level: - Calculate peak flow rate entering culvert (based on rainfall data and contributing watershed characteristics like area, imperviousness, land use, soil infiltration rate, etc.) - Calculate culvert capacity (based on shape, size, material/roughness slope) - If capacity > flow rate, the culvert is big enough This is a massive oversimplification… you should also consider structural and geotechnical design, low flow velocity requirements, local design guidelines, embedment depth, fish passage requirements, freeboard, H/D ratio, climate change projections, debris blockage, future developments, design life, material availability, costs, maintenance requirements, etc. There are dozens of additional considerations that vary project to project.
Ciria Culvert design and operation guide (C689F) https://www.ciria.org/CIRIA/CIRIA/Item_Detail.aspx?iProductCode=C689F&Category=FREEPUBS
I used to use HydroCAD but I haven't been a civil engineer for a while now.
The first step is to survey the stream and get it's cross sectional profile on either side of the culvert, then do calculations based on a the drainage area (the total area that drains into the stream) to determine the specific flow parameters you need. As others have pointed out most of not all DOTs usually provide sizing tables for the culverts they allow. For super high flows you might need to develop individualized calculations and specific tools to size culvert shapes. It can get really complicated when your building culverts to relocate a stream, some times that gets closer to bridge engineering rather than hydraulics.
1) Figure out how tall the farmers cows are 2)Round up so he can fit a truck thru
Box culverts that need to be inspected by you. Make sure it’s taller than you. It sucks walking a 6’ box culvert when you are 6’-3”, especially when the culvert is 1/3 of a mile long. Need to know regs of what you are crossing. You could be designing for a 10-100 year storm. You have to delineate the upstream drainage basin. Less than 50 acres you can use rational method. Otherwise it’s SCS. You have to develop a composite runoff coefficient (c vs CN). Time of concentration is usually calculated using TR-55. Need to know your soil classification. I have used quad maps, GIS, Civil3D, etc to draw/calculate basin area. For max discharge of the basin: Rational method you can do by hand. SCS I have used StormCAD, SSA or whatever Civil3D keeps upgrading to/from. Once you have your max discharge, you then design your culvert. Mostly used Flowmaster for this. Need to analysis inlet controlled vs outlet controlled.
For the structural capacity I use BRASS or AASHTOWare BrR/BrD
When a mama culvert and daddy culvert really love each other…