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Methods for Preventing Erosion

  1. Mar 28, 2016 #1

    ProfuselyQuarky

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    Are there any effective ways for preventing erosion that work on a long-term basis? I’m asking this out of curiosity because there is a cliff side that I live near that I have observed eroding for the past years and it looks as though it is getting rather serious. It’s like this: There is a saltwater bay connected to the ocean, and on either side of the water there are steep cliffs. The top of the cliffs are, in fact, locations for residential homes (the place is actually a pricey area to live). For as long as I can remember, those cliffs have been slowly wearing away. Eventually, the city placed geotextiles kept in place with sandbags and rebar, but this is doing no good. The last time I visited the bay, so much of the cliff had eroded so that the bottom of some of the houses’ balconies were no longer resting on ground (it had all worn away). Is there nothing that can be done? Planting vegetation would be an effort in vain, because the soil is mostly sand (which is probably the cause of so much erosion) and nothing hardly grows except brush and cactus (and even those appear to be dead). Adding retaining walls would be a huge production and an eye sore for everybody, as well.

    Southern California hardly gets any rain, but even light drizzles seem to do damage to the cliff. Is there seriously nothing that can be done? Or are there any options that the city just has not implemented?
     
    Last edited: Mar 28, 2016
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  3. Mar 29, 2016 #2

    Simon Bridge

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    Short answer: depends - what do you mean by "long term" and "effective"?
    In general: no.

    There is no cost-effective way to prevent erosion of the cliff by the normal action of the sea and the wind.
    You could, in principle, protect the cliff by cladding it in a hard material - that material will erode instead, hopefully slower. You can also keep rebuilding the cliff, establish a sea wall, that sort of thing. Planting stuff on the cliff speeds the erosion - tree roots break up the cliff face. Planting along the top of the cliff, or digging culverts, could reduce water run-off over the cliff ... but that probably isn't the main cause of erosion.

    Basically, people with cliff-top properties are dicing with Nature - the trick is to sell up before the cliff erodes the property value as well.
    I live near the kind of place you describe, the city council requires the erosion rate to be taken into account for any new constructions, and that figure is part of the mandatory disclosure.

    Sometimes the rate of erosion is increased my human activity - people cutting steps into the cliff, for example, and rats tunnelling along the bottom.
    Bottom line: you cannot stop the erosion. The best you can hope for is to slow it down.
     
  4. Mar 29, 2016 #3

    ProfuselyQuarky

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    I meant something that will be permanent or something that will prevent serious erosion for a couple of years, at least.
    That's a shame. I thought plants help erosion, but I guess not for cliffs. I don't think a wall of any sort would be an option, either. Too many people go there to walk/kayak/bike for the scenery. There are steps between the cliff at one spot so that the people above can have access to the bay, but aside from , the cliff is untouched. I can't imagine what's going to happen in a few years time.
     
  5. Mar 29, 2016 #4
    I guess the exposed soft rock cliff could be reinforced using steel and cement, but even that would only delay the erosion, wouldn't stop it.
     
  6. Mar 29, 2016 #5

    ProfuselyQuarky

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    How would they drive the steel into the cliff?
     
  7. Mar 29, 2016 #6
    Make holes I guess with a really powerful drill, but that is actually in addition (and an improvement) to my original idea.
    (I was just thinking of surfacing the cliff rock with hard wearing reinforced concrete or similar)
     
  8. Mar 29, 2016 #7

    Simon Bridge

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    Plants reduce erosion to hillsides by reducing water runoff and baffling winds while their roots hold otherwise loose soil together.
    That won't help with a cliff, where they just add weight to the wall while their roots break the rock or whatever apart.
    One of the ways ppl protect cliffs from erosion around here is to pin wire mesh to it then spray with concrete... repeat every few years. I dont think it works well against storms.

    Note: all this is general... for a proper assessment, consult a landscape engineer.

    The end result is the same though... eventually the clifftop properties will be foreshore properties.
    That's just life... stuff changes. Its quite popular in many places to live near a volcano for eg.
    What could go wrong?
     
  9. Mar 30, 2016 #8

    ProfuselyQuarky

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    Thanks for you're reply! I think understand why nothing has been done to the cliff near my home now: because there's nothing to be done :(
     
  10. Mar 30, 2016 #9

    Evo

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    My parents grew up near Galveston, TX, and at one time had considered buying a beach front home. but my parents did some research and found that the current homes on stilts on the beachfront were hundreds of yards in from previous homes on stilts that had been wiped out by a previous hurricane. They decided not to buy, and that summer a hurricane hit and that entire subdivision was gone. The new shoreline was way inside of where the previous homes were. So, word to the wise, do not buy homes that are in areas that are likely to be erased. Sure they may have incredible views, until the views disappear, along with the earth beneath them.
     
  11. Mar 30, 2016 #10

    ProfuselyQuarky

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    Good advice! It's a shame that the beach home are the ones that are millions of dollars, though. But I suppose that if you can afford to by that type of house to begin with, losing it won't hurt too bad.
     
  12. Mar 31, 2016 #11

    jim hardy

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    "National Flood Insurance Program" will replace them ... but don't let me get started on that scam.

    Some places one just shouldn't build anything but a disposable structure.

    To your sandy cliff - will this stuff grow there ? It develops quite a root system.
    http://plants.usda.gov/plantguide/pdf/pg_ange.pdf
    upload_2016-3-31_7-37-28.png
     
  13. Mar 31, 2016 #12

    ProfuselyQuarky

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  14. Mar 31, 2016 #13

    jim hardy

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  15. Mar 31, 2016 #14

    ProfuselyQuarky

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  16. Mar 31, 2016 #15

    jim hardy

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    I only hear about California in the news....

    Big Bluestem is native to America , but i think not California.

    its relative Little Bluestem is a suggested antidote for invasive Japanese Silvergrass.
    https://www.nps.gov/plants/ALIEn/pubs/midatlantic/plants-to-watch.htm
    It too is used for erosion control.
    http://plants.usda.gov/plantguide/pdf/pg_scsc.pdf

    I would find my county agricultural co-op and ask them.
    It's almost an endangered plant so who knows - they might welcome it.

    I scattered some seeds around my yard that i picked along the roadside , US160 in southern Kansas . It seems to need zero care - my kind of landscape plant.

    old jim
     
  17. Mar 31, 2016 #16

    ProfuselyQuarky

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    This is very interesting, thanks for the comments and suggestions. Of course, I'm not going to take it into my own hands to fix the entire problem (obviously), but it would be a good experiment on a small section of land.
    Endangered or not endangered, the HOA in Southern CA is fierce. In reality, they probably won't let anybody touch their precious sand :woot:
     
  18. Mar 31, 2016 #17

    jim hardy

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    As much as i admire Thoreau's spirit of Civil Disobedience, it's not something i should recommend on this forum.

    Then you have to make them think they thought of the way to save their precious sand cliffs.
    Print up the links and give them to the most arrogant, picayune member of the Condo Commando Corps
    not at a meeting, perhaps mail them to him or if you know him slip them at lunch.

    "It's amazing what you can accomplish when you don't care who gets the credit" - Harry Truman

    or, if you live there start some in your own back yard for "show and tell" next year. The roots should be down a foot or two by then.

    My two cents. Overpriced i'm sure.

    old jim
     
  19. Mar 31, 2016 #18

    ProfuselyQuarky

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    Oh! I wasn't going to do it, if that's what you were thinking. I was just saying that it'd be a good experiment.
    :DD
     
  20. Mar 31, 2016 #19

    jim hardy

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    I didn't think of this plant because we didn't have them at beaches i frequented as a kid, around Miami.
    But further north like Palm Beach they are plentiful
    old fashioned Sea Oats
    http://plants.usda.gov/factsheet/pdf/fs_unpa.pdf
    sorta a Saltwater Prairie Grass ?
    It's an East coast plant - i don't know if it'll grow where you are. Last patch of it i saw was in Clearwater Fla, fenced off and posted "protected" .

    Anyhow, food for thought and it's been fun !

    Good Luck .

    old jim
     
  21. Mar 31, 2016 #20

    ProfuselyQuarky

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    Thank you! Your posts are very informative and freakishly entertaining :biggrin:
     
  22. Apr 1, 2016 #21

    256bits

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    That's not entirely true.

    It is somewhat akin to whether the cure is worse than the disease, and evaluation of risk factor.
    Would spending billions of dollars to "protect" the cliffs from their natural state of erosion - I don't think in this case it is due to man made interference with mother nature, to save the collapse of homes worth only millions, in any one local area.
    The soil laid down eons ago from streams flowing into the ocean. The sand, silt, mud, clay are now above the water and through their erosion, provide material for the makeup of the beaches. Completely stop the erosion and where do the beaches aquire the material for their replenishment of that which is lost far out to sea over the years from winter to summer cycles.
     
  23. Apr 16, 2016 #22
    Can you conduct tests to see the nutrient content in the cliff side?

    In the vivarium community, it is common to run light (let me emphasize light) streams down the artificial structures in the tanks and then grow moss, algae, and assorted plants to strengthen them, while the streams supply them with water to grow.

    I know it's way out there, like thousands of miles out there, but you can take a hose, cut holes at intervals in the holes, and build a pump that pushes water through the hose. Run the hose around the rim of the cliff, and make an algae wall that protects the cliff from erosion. You can also plaster a nutrient rich substrate across the wall. Maybe you can use hydroelectricity and solar power to power the pump using an electric motor.

    You probably shouldn't take that seriously, as I am not a geologist. However, it does sound interesting, so interesting in fact, that I might have to try it on a small sandstone cliff by where I live.
     
  24. Apr 16, 2016 #23

    jim mcnamara

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    You are talking about restraining thousands of tons of matter with an algal mat. The concept is valid for VERY small objects that have some unfailing components behind them like a small rock. Eroding cliffs fall apart in part because of the movement of water from wetter areas behind the cliff face out towards the drier exposed face. The particles loosely bound together in alluvial material (soils with gravels, cobbles) become slippery when they get wetter. As the size of the stuff you want to restrain in your problem space becomes a larger value, the mass the mass of that stuff goes up exponentially. Home aquariums and palisade cliffs are worlds apart.

    The technical term for resisting movement in the cliff material is shear strength. Water influx decreases it. It gets looser, and becomes a target for failure.

    Example: After a rainy period on steep hills, mudslides and other slips occur far more frequently. This is generally lumped under the concept of mass wasting. See:
    https://en.wikipedia.org/wiki/Mass_wasting

    The point is among lots of other things: the material is loose, shoring it up may work temporarily, but it also creates more mass out at and beyond the next point of failure. Massive removal of material and replacing it with something like the Hoover dam would be required. You cannot do that and leave houses in situ. And homeowners cannot afford their own version of a Hoover dam, US presidential candidates notwithstanding....

    It's great that you want to experiment, but in the case presented by the OP you would have to invent something (AFAIK) that is physically impossible. Vegetation on hillsides with material at the angle of repose can be restrain creep for long periods, not forever.
    http://www.oregonlive.com/portland/index.ssf/2015/12/mudslide_on_us_30_brings_st_jo.html

    Seaside cliffs (often called palisades) of the same material as the hillsides I just mentioned are already pretty much beyond the angle of repose. You have to rebuild the cliff with something that does not have the angle of repose problem. And has sufficient footing and mass to restrain the loose pile of soils behind it. Hoover dam with double thick restraining walls is my choice.
     
    Last edited: Apr 16, 2016
  25. Apr 17, 2016 #24

    ProfuselyQuarky

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    This would be so interesting to try! I like this experiment a lot. Thanks @twiz_ :)

    . . . only it'd definitely not legal for any unauthorized person to be doing that . . . and if it was, the entire cliff would crashing down in a sandy heap--yep, the cliff's that touchy :)

    And thanks, too, @jim mcnamara, very informative :)
    This is what I kind of figured. Affordable fixes will never last forever.
     
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