Riprap channel lining is used when natural soils or vegetated stabilized soils in a channel are not adequate to prevent channel erosion. This BMP is often used when a permanent ditch or pipe system is to be installed and a temporary measure is needed.  

*The contents of this guide are to provide a general overview only. It is the users responsibility to ensure all BMPs utilized on their project meet the requirements of their state and local jurisdictions.

Find it in the Stormwater Management Manual:

Eastern Washington          Western Washington

Riprap Channel Lining Installation:

• Since riprap is typically used where erosion potential is high, construction must be sequenced so that the riprap is put in place with the minimum possible delay. 
• Disturb areas awaiting riprap only when final preparation and placement of the riprap can follow immediately behind the initial disturbance. Where riprap is used for outlet protection, the riprap should be placed before or in conjunction with the construction of the pipe or channel so that it is in place when the pipe or channel begins to operate. 
• A lining of engineering geotextile shall be placed between the riprap and the underlying soil  surface to prevent soil movement into or through the riprap. The geotextile should be keyed in  at the top of the bank. 
• Geotextile shall not be used on slopes > 1.5:1 as slippage may occur. It should be used in  conjunction with a layer of coarse aggregate (granular filter blanket) when the riprap to be  placed is 12 inches and larger. 

Riprap Channel Lining Maintenance:

• Inspect channel lining for debris and signs of erosion
• Replace riprap as needed