Sunday, 3 June 2012

Excess water in the garden? Field drains to the rescue ~

Surface water that cannot drain away can rot or even drown plants.  It can also make a garden dangerously slippery as I have found to my cost: last summer I took a bad fall in a wet spot in our garden, nearly tearing the ligaments in my knee as my other leg went straight out from under me in quite a different direction - ouch!  Although the property here is on a steep hillside surface water is still a problem. 

Something had to be done!  I'm 'only' a tenant here, so what could I do?  No one else was going to do anything so I had to work out some kind of solution myself.  The first thing to do was to have a closer look at the problem. 

I found that there were three field drains which hadn't been linked with each other.  At the right hand end of the top terrace one of them stops short at the top of a steep pathway and after heavy rain it becomes a water slide.  The point at which the surface water from this accumulated with the other two was where I took my tumble.  I simply didn't see the wetness.  

Partial solutions of this sort are exasperating as they don't solve problems, they simply move them around.  I certainly wasn't about to lay out my own money to buy further amounts of plastic drainage piping or spend weeks digging trenches which no one would thank me for, so I worked out my own partial solution which should at least reduce the scale of the problem.  I did what I could.

In the top right hand end of the garden I dug the ground over thoroughly and planted two shrubs: a hebe and coprosma.  These obliging shrubs grow almost anywhere.  I also put in a border of ferns along the back as well as some other plants.  As they get better established they will absorb some of the excess.  That's a clump of violets next to the puddle.

But perhaps more importantly their roots will provide a network of growth which should reduce the volume of run-off by slowing down the movement of water through the earth.  If this were my own place I'd look at putting in flax and tussocks which would be more effective, but a lot of people find these sorts of plants too big and difficult, so the present scheme was the best compromise I could arrive at.  None of it cost me anything.  By the end of next summer the shrubs will be as tall as the fence and will have bushed out nicely.  Here it is on a dryer day all nicely mulched for the winter:

The muddy area below the bottom terrace was another matter: I found that a plastic field drain empties out at the top of the lawn just near the middle of the terrace.  When we moved here last winter a half-hearted gesture of a ditch ran from the open end of this drain along to the right hand end of the terrace where another piece of plastic pipe lay concealed beneath rough grass and few rocks.  It looked as if it was intended to carry excess water from one point to the other but after heavy rain the lawn got very squelchy and it didn't seem to work as it should.  It was a handy spot in which to park some of my pot plants while I decided what to do with them.  That's the steep path I mentioned, at the right:

The trouble with the ditch was that Rewi more than once turned his ankle by stepping into it when he walked past that corner.  You can see how easily this could happen:

I decided it had to go.  I filled it in with some rocks to assist any lying water to drain to some degree, piled in about a barrow-load of earth and planted it up with plants that are tolerant of wet spots:

Unaware of the amount of water that actually did run through it I didn't leave enough of a passageway under the surface for this to drain through so it wasn't long before it became very boggy indeed: I could tip water onto it and it simply sat there - mud pie!  I realised I would have to dig it right out and see if I could make a better sub-surface waterway.  We had plenty of mussel shells from Rewi's foraging so I decided to use those to fill it.  I dug out the plants and put them into crates:

The mud was very squelchy indeed and not what I wanted to have on the lawn as it would be difficult and messy to remove, so I got out the old thermal-backed curtain which has been so useful in the garden.  This photo is from a different project, but the curtain served the same purpose:

Having dug a decent sized trench and exposed both ends of the field drains I covered the open end of the lower pipe with wire netting to prevent earth and shingle from falling into it and lined the bottom of the trench with large rocks and then shingle.  That should prevent the ditch from loosing its structure and still allow the passage of water through gaps in the rough shingle.

I then 'roofed' it with mussel shells with the curved side upper-most to prevent loose earth from clogging the whole thing up...

...filled it in, carefully re-planted it, replacing the earth as I did so, and covered it all with mulch:

Since then the back lawn has definitely seemed drier and the top garden hasn't been so wet.  Last night we had heavy rain so this morning I went outside and carefully walked back and forth to see where the squelches were.  Good news: none below the bottom one, and although there was clearly still too much surface water in the grass of the pathway, there was no water standing in the top garden either.  

I'll be interested to observe how things go after heavier rain, but feel that I have made some progress.  The main thing is that the situation has definitely improved, the patches of garden I've worked on look great, and none of it cost me anything.  I like doing things myself if I can. 

If I were putting a new set of field drains in my own place I'd definitely want to have a more comprehensive scheme in place.  I found this site in which the site manager has generously shared his professional expertise.  It looks first rate:
If you find their site useful I encourage you to consider making a donation for site maintenance via their Donate button which is on their 'About Us' page.  It's a non-commercial site.

It's winter now, and I've largely abandoned my work in the garden, letting most of the weeds have their way until the weather warms up again.  I don't feel the need to have the garden tidy all the time or consider it good practice - the ground needs to be left somewhat to its own devices during its rest time, and the insects, whom I think of as The Little People, need somewhere to live during the winter months.  It will be time enough for me to stir things up in the springtime.

We still have plenty of veges to hand: parsnips and carrots, which don't mind being in the ground during our winter, lots of greens with silver beet and rocket, and the perennial herbs are still plentiful.  Perhaps the greatest triumph of all is that the $20 I spent on potato seed last spring has resulted in a harvest which we are still enjoying: over seven months worth of delicious fresh potatoes!  Now I call that good value and good eating!  May you also enjoy such bounty.

A companion article (June 2015) about managing flood water on this hillside property by digging ditches can be found here:
My other articles about working in the garden can be found here:

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