USBR Stilling Basin Dimensioning – Advanced Tool

Suggests basin type (Type I / II / III / IV) and indicative dimensions (length, block sizes, sill height) based on approach Froude number, conjugate depth and tailwater at the basin.

↗ Basin Type Selector (IS / USBR)

0 Report Info (optional)

These fields are only used for the PDF title block and XLSX export (project documentation).

1 Flow Conditions & Jump Parameters

Rectangular section assumed at basin entrance. Use values at the toe of the spillway or outlet.
Total discharge entering the stilling basin.
Clear width of flow entering the basin.
Supercritical depth at basin entrance (just downstream of spillway).
Depth corresponding to downstream rating curve / river level at basin.
Invert difference between upstream pool and basin floor (for head check).

2 Basin Type & Dimension Multipliers

Choose a basin type or allow auto-selection based on Fr₁ and tailwater match. Dimension multipliers can be tuned to local code charts or project preferences.
Defines what “tailwater matched to y₂” means.
Plain apron basin length; typical 5–7.
High-velocity basin with special floor.
Baffle basin often uses 3–4 y₂.
Low-Froude basins can be compact; final values must follow charts.
Chute/baffle block height; typical 0.6–0.8 y₂.
Block thickness in flow direction; typical 0.25–0.4 y₂.
Clear spacing between blocks; typical 0.75–1.5 y₂.
End sill height ≈ 0.07–0.15 y₂ in many layouts.