Culvert Design Tool

Culvert Configuration

Culvert Type

Material Type

Number of Barrels

Dimensions

Diameter/Height (ft)

Width (ft)

Length (ft)

Slope (%)

Flow Parameters

Flow Input Method

Peak Flow (Q) (cfs)

Water Levels

Inlet Elevation (ft)

Outlet Elevation (ft)

Tailwater Depth (ft)

Consider Tailwater Effects

Hydraulic Parameters

Manning's Roughness Coefficient (n) Default values set based on material type

Entrance Loss Coefficient (Ke)

Exit Loss Coefficient (Kx)

Analysis Options

Estimate Scour Potential

Check Velocity Limits

Check Submerged Conditions

Design Safety Factor

Units

Imperial (ft, cfs)

Metric (m, m³/s)

Results

Culvert Capacity

Maximum Flow Capacity: 0 cfs

Design Flow: 0 cfs

Capacity Ratio: 0%

Flow Characteristics

Flow Velocity: 0 ft/s

Flow Regime: -

Froude Number: 0

Headwater Analysis

Headwater Depth: 0 ft

Control Type: -

Submergence Ratio: 0%

Scour Analysis

Scour Potential: -

Estimated Scour Depth: 0 ft

Velocity Check: -

Hydraulic Profile

An interactive calculator for culvert sizing and hydraulic analysis

Enter your design parameters on the left and click "Calculate" to analyze your culvert design.

The tool is pre-populated with example values to get you started.

Quick Tips

Use the tabs to organize your inputs
Hover over labels for tooltip explanations
Switch between direct flow input and rational method
Check advanced options for more control

About Culverts

Culverts are structures that allow water to flow under a road, railroad, trail, or similar obstruction. Proper design ensures adequate water flow while maintaining structural integrity.

Common culvert materials include concrete, steel, and plastic, each with different hydraulic characteristics.

This tool helps you design and analyze culverts for hydraulic performance. Follow these steps:

Select the culvert type and material from the dropdown menus
Enter the culvert dimensions (diameter/height, width, length, slope)
Provide flow parameters either directly or using the Rational Method
Set water level information (inlet/outlet elevation, tailwater depth)
Adjust advanced parameters if needed (roughness coefficients, loss factors)
Click "Calculate" to analyze the culvert performance

Culvert Types

Circular: Round pipe, most common for small to medium flows
Box: Rectangular shape, often used for larger flows
Elliptical: Oval shape, provides more vertical clearance
Arch: Semi-circular top with flat bottom
Pipe-Arch: Compressed circular shape for low clearance

Material Types

Each material has different roughness characteristics that affect flow:

Concrete: Smooth surface, low roughness (n ≈ 0.012-0.015)
Steel: Moderate roughness (n ≈ 0.012-0.024)
HDPE: Plastic material, very smooth (n ≈ 0.009-0.015)
CMP: Corrugated metal, higher roughness (n ≈ 0.022-0.027)

Key Outputs

Maximum Flow Capacity: The maximum flow rate the culvert can handle under the given conditions
Headwater Depth: Depth of water at the culvert inlet
Flow Velocity: Speed of water through the culvert
Flow Regime: Whether flow is subcritical (slow, tranquil) or supercritical (fast, rapid)
Control Type: Whether culvert performance is limited by inlet or outlet conditions
Scour Potential: Indicates risk of erosion at culvert outlet

Interpreting Results

A Capacity Ratio below 100% means the culvert can handle the design flow
Velocities between 2-10 ft/s are typically desirable
Subcritical flow (Fr < 1) is generally preferred for culverts
High scour potential may require energy dissipation measures