RIP RAP INFLOW PROTECTION

Definition

A temporary or permanent lined drainageway installed to convey concentrated runoff into sediment traps and basins or down steep slopes as applicable. Rip-rap inflow protection consists of the installation of rock or recycled concrete equivalent in a flow channel for stabilization.

Purpose

The purpose of rip-rap inflow protection is to provide stable conveyance of concentrated runoff down steep slopes, (i.e. into temporary sediment traps and basins) thereby preventing erosion of the flow channel. 

Conditions Where Practice Applies

Rip-rap inflow protection is required where the slope of a drainage way contributing to a sediment trap or basin exceeds 10:1 but is less than 4:1. Runoff may be directed to the inflow device by means of dikes or swales. 

Design Criteria

Rip-rap inflow protection shall be 4"- 12" rip-rap (min.), underlain with Geotextile Class C and placed from the ditch overfall elevation to the bottom of the trap or basin when the inflow slope is between 4:1 and 10:1.  Slopes flatter than 10:1 shall be stabilized in accordance with temporary swale or earth dike criteria as applicable. For slopes steeper than 4:1, see gabion inflow protection.

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