Thursday, January 28, 2010

why putting rock on the beach is a bad idea.


"coastal armoring" [also called shoreline/coastal pr
otection structures and hard structures]


coastal armoring protects infrastructure (roads, houses, water treatment plants, parking lots...) NOT the beach from coastal erosion.

riprap revetments (engineered rock that is placed on the shoreline to protect property from coastal erosion) - example: rock proposed at Sloat Blvd.

Photo by Surfrider Foundation. Riprap revetment in southern California


and seawalls (vertical walls that are built in front of structures or along cliffs to stop coastal erosion) - example: O'Shaughnessy Seawall on northern OB

Photo. O'Shaughnessy Seawall in SF.

Photo by Surfrider Foundation. Seawall in Monterey.
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coastal armoring can cause the following NEGATIVE impacts to the beach:
1. passive erosion - the rock or seawall cause additional coastal erosion to occur down-drift and on the edges of the structure.
2. placement loss - rocks placed on the beach cover the beach and at high tide can block lateral access on the beach.
3. active erosion- beaches can narrow due to changes in beach dynamics and wave reflection.
4. public access issues - rock can block beach access and cause dangerous conditions for beach users and surfers.
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MORE INFO AT:

Surfrider Website -
http://www.surfrider.org/seawall/

Scientific NOAA document titled: The Impacts of Coastal Protection Structures in California's Monterey Bay National Marine Sanctuary

UCSC Professor Gary Griggs article on California's Eroding Shorelines

4 comments:

  1. Thank you for this post, I've read a good majority of the content listed here and some additional Google-esque reading of my own.

    I feel this should be a difficult issue for any reasonably minded person to discuss and/or address. It's very easy to say putting rock on the beach is "bad" - but at what point does saving beachfront property (in this case the great highway) take precedence over the "environment?" Some would say it should never take precedence.

    I think its a very delicate balance and in all honesty I lean towards the the populous taken precedence over the environment. I realize this is a statement fraught with danger. On the one hand, some clearly feel the environment is not important at all and have little concern for the impact of the populous on it. Others have so much concern for the environment, they would rather humanity be destroyed than it leave any trace upon the environment.

    Hopefully, there is a responsible middle ground somewhere - especially in this situation. Does the populous traffic on the great highway outweight the potential impact of placing rocks on the beach? If Ocean Beach disappears as a result, does it negate the need for the great highway in its current path? If we retreat and allow the great highway to be swallowed up - what next? Do we all the avenues to be swallowed up as well? Given the natural course of erosion, all the aves should disappear into the sea. So at what point do we intervene to protect the environment we inhabit from the environment that is encrouching upon us?

    I appreciate you advocate sandbags rather than rock - although I'm not sure the difference in impact to the beach. That would make for a good post, if nothing else to provide a link.

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  2. i just posted about sandbags. there is not all that much information out there about them. let me know if you can find any more good info.
    thanks!

    ReplyDelete
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