Riprap and Concrete Blocks Examples

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The riprap apron is one of the most common forms of outlet protection on small dams. The riprap apron is typically a flared transition constructed at zero grade for a distance downstream that is related to the conduit diameter. Although the riprap apron provides relatively little energy dissipation, it can provide very effective erosion protection at the conduit outlet by armoring the turbulent transition area. The key design parameters of the riprap apron are apron length, apron width, riprap thickness, and riprap size.

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  Transitional riprap apron downstream for a type VI stilling basin to prevent scour.

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  The grouted riprap has performed well although some of the larger rocks in the foreground are displaced immediately downstream of the concrete apron.

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  Gabion-lined basin. The earthen basin was used to facilitate construction access and has been removed.

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  Armorflex Blocks in downstream channel.

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  Outlet protection using Articulated Concrete Blocks and A-Jacks®.

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  Outlet protection using Articulated Concrete Blocks and A-Jacks®.

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  Examples of Articulated Concrete Block (ACB) revetment systems.

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  Aerial photo of riprap apron.

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  Full channel flow through riprap apron after construction.

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  This photo shows the same apron as the previous photo. The erosion evident downstream would have progressed to the toe of dam without the apron.

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  Grouted Riprap Apron.

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  Gabion Basin.

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  Gabion Basin.

Note: The content on this page was originally created as part of DamOutletWorks.org (DOWL, 2018). It has subsequently been updated and reformatted as part of the Dam Safety Toolbox.
Revision ID: 4820
Revision Date: 12/02/2022