Swales?

Discussion in 'Put Your Questions to the Experts!' started by hoggie, Jul 11, 2018.

  1. hoggie

    hoggie New Member

    Joined:
    Jul 11, 2018
    Messages:
    7
    Likes Received:
    3
    Trophy Points:
    3
    Gender:
    Female
    Climate:
    South UK - temperate?
    Can someone explain swales to me please?

    I have waded through what seems like a whole library of websites talking about swales (that is how I found this website) and I understand the concept of holding back the water etc.

    But...... there is talk of a "bloom" underneath the swale where the water seeps underground and affects the land next to it. My question is, how far do these reach? I am looking at digging some swales to try to help my half acre plot, but am having difficulty visualising how much land a swale will effect.

    If anyone can advise on this I would be extremely grateful

    TIA
     
    songbird likes this.
  2. songbird

    songbird Senior Member

    Joined:
    Sep 12, 2013
    Messages:
    1,780
    Likes Received:
    142
    Trophy Points:
    63
    Occupation:
    gardening, reading, etc
    Location:
    near St. Charles, MI, USoA
    Home Page:
    Climate:
    -15C-35C, 10cm rain/mo, clay, full sun, K-G Dfa=x=Dfb
    this varies so much by soil types and rainfall...

    is your area arid enough that deeper swales are needed?

    in some locations it may be ok to just work on terracing to keep the
    topsoil from moving or just to make sure there are ground covers in
    place to keep erosion at bay.

    getting back to your initial question though a swale is an on contour
    water retaining excavation. how deep and how big to make it depend
    upon how much water you wish to stop and allow to sink in.

    in an arid or semi-arid climate you want to capture as much moisture as
    possible. in areas where there are more regular rains perhaps you only
    want a swale in place to capture some of the water and then to let the
    rest run off in a more controlled and gentle manner (keeping erosion to
    a minimum and holding on to the topsoil).
     
  3. hoggie

    hoggie New Member

    Joined:
    Jul 11, 2018
    Messages:
    7
    Likes Received:
    3
    Trophy Points:
    3
    Gender:
    Female
    Climate:
    South UK - temperate?
    Hi Songbird

    Thank you for this. It is hard to say - at the moment the "decent" topsoil is non-existent having been washed off due to being exposed, and the ground is very sandy on the top centimetre or so, and then rock solid underneath. At the moment I just want to slow things down a bit, the grass is starting to recover a little and we are starting to get a covering of burdocks and nettles which I am envisaging will at least help the soil hold together and re-build a little. So at the moment I just want the swales to slow things down a little, and hopefully help to re-build the soild as well. I am taking the view that we will see how things progress and adjust as necessary. Fortunately nothing is on a huge scale so it isn't too bad if I need to alter anything.

    I was asking about the bloom as I was trying to work out if this should dictate the spacing of the swales.
     
    songbird likes this.
  4. 9anda1f

    9anda1f Administrator Staff Member

    Joined:
    Jul 10, 2006
    Messages:
    3,046
    Likes Received:
    199
    Trophy Points:
    63
    Gender:
    Male
    Location:
    E Washington, USA
    Climate:
    Semi-Arid Shrub Steppe (BsK)
    Hi Hoggie,
    Here's Geoff Lawton's swale "plume" video:
     
    Bryant RedHawk and songbird like this.
  5. songbird

    songbird Senior Member

    Joined:
    Sep 12, 2013
    Messages:
    1,780
    Likes Received:
    142
    Trophy Points:
    63
    Occupation:
    gardening, reading, etc
    Location:
    near St. Charles, MI, USoA
    Home Page:
    Climate:
    -15C-35C, 10cm rain/mo, clay, full sun, K-G Dfa=x=Dfb
    with little topsoil and hard underpan it will be hard to hold a swale in place if you get a heavy rain. somehow you'll need to hold the soil in place until it gets anchored to the subsoil.

    do you know how to do area and volume calculations? because pretty much your soil has a certain capacity to hold moisture so if you have a certain depth of soil then you can roughly figure the size of the swale you need to capture and slow that much water down. assuming your subsoil drains very slowly or not at all will also affect your calculations.

    the other considerations are your slopes and how stable they are when they get saturated. in some areas the soils move too much if they get too much water in them (landslides in California after heavy rains being one example).

    you mention only having two types of plants growing there (burdock and nettle). is there some way you can increase your diversity of cover? you can look around for fairly inexpensive cover crop seeds (we can get those at the local grain elevators for a few $ per pound). it's nice to have some variety. you can also put in some vegetable seeds in the mix to see how they do which will also give you some indications of conditions, but also give you some food in return. :)
     
    9anda1f likes this.
  6. Rick Valley

    Rick Valley New Member

    Joined:
    Sep 8, 2018
    Messages:
    2
    Likes Received:
    1
    Trophy Points:
    3
    Gender:
    Male
    Climate:
    mediteranean
    Hi Hoggie; Songbird has given good advice and asked good questions. On a half-acre there's not too much room for big earthworks (I work 2/3 of an acre at home so I'm in a similar situation) I too have a beastly hardpan, with a fair amount of crushed rock in upper layers, (It was a used car lot for a time!) and here soil development seems to be helped most by deep digging, and putting woody debris in before covering it back over. (Fukuoka did this in his upland orchard, as did R. T. Mazibuko in S. Africa) Five years in, I find myself creating small swales to obtain soil to add to my extensive compost piles. As Songbird said slope is an important variable to consider; you didn't mention your topography. (For my site slope is measured in millimeters per meter, so raising a mound is as impactful as digging down- the only runoff I see is off macadam or roof.) Have you dug a soil pit and had a look at what the layers are like? You'll definitely want to avoid building barriers to movement, so get familiar with the best ways to get around your place before digging big features in. Different from bigger acreages your "vehicle" will likely be a small cart or wheel barrow,so start hauling stuff to figure out your best layout for paths. All this said, also try a small swale and see what happens: instead of machinery use pick and shovel. (you did say "hardpan!) The process will be useful in learning the soil layers and by seeding the freshly excavated soil berm with a cover crop mix you'll learn lots about your place and how to proceed. Go slowly, and don't over-work your body in the process, pain is not fun.
     
    9anda1f likes this.
  7. songbird

    songbird Senior Member

    Joined:
    Sep 12, 2013
    Messages:
    1,780
    Likes Received:
    142
    Trophy Points:
    63
    Occupation:
    gardening, reading, etc
    Location:
    near St. Charles, MI, USoA
    Home Page:
    Climate:
    -15C-35C, 10cm rain/mo, clay, full sun, K-G Dfa=x=Dfb
    organic matter is always a good thing to have available, but if you don't have some
    way to hold it on a slope all those nutrients and benefits are heading downhill...

    digging a deeper swale to trap and keep your nutrients and any moving topsoil
    is likely going to help, you can do what some longer term farmers do (they actually
    move the soil that's gone downhill to the bottom of the field back up to the top as
    a normal part of their routine). it's work for sure, but if you think of long term
    sustainability it's gotta be done if you don't have a level site with good cover in
    place...

    i'm actually quite happy to be on a fairly level area here because other than the flash-
    floods i have to guard against from the south farmer field i don't have to worry too
    much about my topsoil moving that much. i still do have some earthworks to do to
    control one erosion gully, but it is pretty slow forming and i have much harder issues
    to cope with for the moment...
     

Share This Page

-->