Interactive engineering model
Culvert outlet riprap apron
Explore the subcritical circular-culvert HEC-14 path as discharge, barrel diameter, and bounded tailwater select a stone class and apron geometry.
Preparing the 3D model...
A cutaway culvert runs full through a headwall with a punched opening and discharges onto a riprap apron that starts at the outlet face and flares from 3D to W = 3D + 2L/3 over its length. Stones are seeded on the blanket surface at the selected D50, a bedding band sits under it, and the jet spreads across the apron into an excavated outlet channel holding the tailwater pool. Reference stones compare the required D50 with the selected class, and dashed markers show the 0.4D and D bounds that govern it.
Focus the 3D view and use the arrow keys to orbit, plus or minus to zoom, and Home to reset the view.
Text explanation and non-WebGL fallback
A cutaway culvert runs full through a headwall with a punched opening and discharges onto a riprap apron that starts at the outlet face and flares from 3D to W = 3D + 2L/3 over its length. Stones are seeded on the blanket surface at the selected D50, a bedding band sits under it, and the jet spreads across the apron into an excavated outlet channel holding the tailwater pool. Reference stones compare the required D50 with the selected class, and dashed markers show the 0.4D and D bounds that govern it.
Important: This artifact is constrained to subcritical circular-culvert flow. Use the calculator's normal-depth input and HEC-14 Equation 10.5 adjusted rise for supercritical flow.
The numeric controls and readouts remain usable if WebGL is unavailable. Drag or swipe the 3D view to orbit and use a wheel or pinch gesture to zoom. With the 3D view focused, use the arrow keys to orbit, plus or minus to zoom, and Home to reset. The complete numeric lesson is also keyboard-accessible in the adjacent controls and readouts. This model is an educational aid and does not replace applicable design standards or professional review.