HY8:Riprap Basin and Apron

Riprap Basin and Apron

The input variables required for this calculation is the following:

• Condition to compute Basin Outlet Velocity — The user can select Best Fit Curve or Envelope Curve. The user should choose Best Fit Curve if the flow downstream of the basin is believed to be supercritical. If the flow downstream is believed to be subcritical, the user should choose Envelope Curve.
• D50 of the Riprap Mixture — Mean diameter (by weight) of the riprap to be used.
• DMax of the Riprap Mixture — Maximum diameter (by weight) of the riprap to be used.

The design criteria for this basin was based on model runs in which D50/YE ranged from 0.1 to 0.7; values outside this range are rejected by the program.

The following figures show riprap basins and aprons.

Variables from the figure

• h_S — Dissipator pool depth
• W₀ — Culvert width
• TW — Tailwater depth
• y_e — Equivalent brink (outlet) depth
• d₅₀ — Median rock size by weight
• d_max — Max rock size by weight