Simple dams for damp gullies?

Discussion in 'Designing, building, making and powering your life' started by void_genesis, Jul 17, 2014.

  1. void_genesis

    void_genesis Junior Member

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    Hi everyone

    I have a damp gully that runs down from a couple of dams into our permanent creek that is often trickling with water but dries out a bit during droughts. I am interested in building some low
     
  2. S.O.P

    S.O.P Moderator

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    I can't help you other than linking you to some further information I pulled out of my brain:

    https://www.fao.org/docrep/012/i1531e/i1531e.pdf - this is the 118 page "Manual on Small Earth Dams".

    https://www.eabooks.com.au/epages/eab.sf/en_au/?ObjectPath=/Shops/eabooks/Products/9780858259577 - this is the book that I've seen recommended but I'm not sure if you could find it cheaper somewhere.


    Personally, I think your theory is sound but by hand I would probably rename them to settling ponds. And you know what I'm going to say about the dam wall because wood ain't going to cut it and ther term "grasses" is just too ambiguous for me. Starts with a V, it can be inundated for up to 4 months, keeps improving with age, grows higher with silt against it..... And if you didn't want it filling with silt every time it flooded, I'd surround it with that special plant to hold back it back from all aspects.
     
  3. songbird

    songbird Senior Member

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    i'd put most of my effort into the top areas, widening the catch areas as much as possible to hold the water up high. then as that is done, work down the next step... as each layer gets established that helps keep the erosion down and the lower layers catch what you disturb from up above.

    wood is ok as a temporary support as long as you plant other things to replace it as it decays. if you have clay, then burying wood in clay and if it is always moist then the wood may not decay much at all. i've dug up wood pieces here from over 150yrs ago.

    the other considerations are the overall stability of the area, to make sure that adding/holding more water will not cause slipping/sliding of the entire hillsides. yes, tying into bedrock or deeper layers is a good thing if you are making a larger impoundment as failure would be catastrophic for the stream or others downhill.
     
  4. sweetpea

    sweetpea Junior Member

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    I really like this guy on YouTube Engineer 775. He has several videos on developing a spring, and I particularly like this plastic dam and PVC pipe device he's made:

    https://youtu.be/hKxdAesHk9M

    :)
     
  5. void_genesis

    void_genesis Junior Member

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    Thanks for all the advice- I think pond would be a better description than dam.

    The area is on a creek flat with maybe one meter fall across a 50 m length of gully, so settling pond would be a better description. Starting from the top down sounds good- water can really pick up momentum. The creek floods about once a year, so no one builds important structures on it, and if a pond burst the impact would be pretty minimal. The soil is clay, so I will give the wood a go to make up some of the structure. Looks like another dry spell is coming, so that will give me a chance to get in there without getting too muddy.

    Thanks for the links- I'll give the resources a good reading before I get started.
     
  6. S.O.P

    S.O.P Moderator

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    Any soil you lose though, even if small, is still a loss. Changing the flow in the water could have repercussions somewhere close that you can't be aware of. Once the berm is formed, the flood water could scour out behind as the water rises over and down again or any other permutations.

    I'm going to sound like a broken record, but I'd make the grasses your first port of call before any digging so you can catch and store anything you lose. Check out this presentation of Vetiver in floodways in Australia, particularly the lead up to Slide 4. Slide 7 can show how a young plant could cope with its first flood and how you put the plants across the flow to slow and deposit:

    https://picasaweb.google.com/VetiverClients/VetiverSystemsForFloodControl#5012248023003889602


    Maybe Slide 10 and 11 out of this one could show why it would be good to start securing before any moving:

    https://picasaweb.google.com/VetiverClients/VetiverSystemForLeveesAndSeaDykes#5014395893198948210


    https://picasaweb.google.com/VetiverClients

    Plus, if you design it well, you could save silt being deposited elsewhere and keep it on your block from further upstream.
     
  7. songbird

    songbird Senior Member

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    thanks S.O.P., in rereading what i wrote i see where your reply certainly improves upon what i said. yes, it is very important to make sure that the downstream is protected from any upstream inadvertent movement of debris. straw bales or fabric fencing are often used for construction projects around here to prevent such troubles. well worth it. never want to be caught out by a sudden squall or storm.
     
  8. S.O.P

    S.O.P Moderator

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    I didn't mean to tread on your toes, you were right but I just had to slide some Vetiver stuff in there as I can't help myself.

    I envisioned him creating the pond site with a Vetiver impoundment and then digging into it a year later.

    I also just came across this Brisbane, Australia gully project using Vetiver and it shows the growth rates and what it can manage.

    https://www.vetiver.org/AUS_Beaudst Gully.pdf
     
  9. bazman

    bazman Junior Member

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    One idea is to use caged rock or recycled concrete walls, these will allow flow to start but will slowly block up with organic matter allowing a back fill of water. Make sure you think about where the water overflows, overflows into/onto rock will help reduce/stop water from cutting out soil. You can buy ready made cages or make your own.
     

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