Drainage - serious solution needed

[JimmerG]

Hi all,

I've got an allotment that has a very slight slope - and you've guessed it.... the bottom 1/4 is currently underwater.

I've done all the adding of organic matter that I can do - but its still very clayey. Its's probabaly smething to do with the solid/pure/rock hard layer of clay that exists about a foot and half down under the top soil.

I'm now thinking of digging a proper drainage channel across the bottom end. Has anyone done this? How did you do it? How deep/wide did you dig it - did you fill it with brick rubble/gravel and then stick soil on top? Should I dig the trench on a slant and dig a big deep sump at one end?

So many questions... but I have so many onions underwater!!!!

Thanks awfully

J

[Nicos]

I'm just wondering......

On our previous two lottie sites- one private and one Council owned- both had clay drainage pipes which needed checking from time to time in case they'd collapsed.
I think they were linked in with the surrounding field drainage systems.
Is your lottie near housing? If you alter your drainage, you could affect gardens- and you're not OK to do that.
If it's near fields, perhaps a word with the local farmer to see if there are in fact any drainage channels/ditches near you which may be blocked- and he may not know about and want to clear for his own benefit.

I was really surprised that both sites- no where near houses had drainage systems...worth looking into firs eh???

[JimmerG]

Nicos - its a good point, but I'm pretty sure there is no drainage system what so ever, but I will try and find out. Many of the other allotments on the site are under water aswell.

J

[weekendwellies]

No good for this year, and it may take a lot of effort, but could you build up that area so that it is more level with the top part, and the water table is well under the soil surface.
Alternatively, put in a nature pond for the frogs and insects

[JamDunc]

Hey JimmerG,

My allotment when I got it had one part which was always under water and was surrounded by unused plots so to kill the two proverbial birds (no birds were harmed in this endeavour!) with one stone, I dug a trench about 1 1/2 spits down all the way around my plot. I also added a sterlingboard panel all around the inside which stops weeds and pests getting into my plot from plots next to me.

But it also helps with the drainage as the water goes to the lowest point, which is in the trench. Also the soil I dug out was weeded and added to my plot which raised it up slightly.

Now other people might contradict me here as I'm still fairly new to the whole allotment thing but I would suggest digging a trench at the lowest point and also along the two adjacent sides. This would allow run off not only at the bottom but also at the sides whilst giving you extra soil to build up the low point. It is a lot of work though, albeit, with you not needing to worry about weeds or bugs you can probably ignore the sterlingboard part!

Hope that helps

Jam

[geoff]

How old or well established is your allotment site? I think our grandfathers, and before them would have been unlikely to put allotments on sites that would be flooded. It is more likely that the drainage has failed or changed over time
See if you can check the dates. and look for new building work like housing or new roads. Also have a wander round the environs (posh, eh?!) of the site to locate any old ditches, drainage channels, culverts, land drain outfalls and so on, and see if they are still working
Also ask the council, they should have records of such things. If all that fails, you could always ask the council to install a land drain, but I doubt if they will give it a very high priority. Try to get the council's Allotment Officer to visit the site and see the problem firsthand
If the ditches are blocked, it will probably be quicker if you and your fellow plotholders cleared it yourselves

[Snadger]

I just wonder if the bottom of the plot leads on to waste land and is that waste land below the level of your plot?
Its no good digging a French Drain (open trench) if the water has nowhere to go. You need an outlet to lower land or a soakaway.

[JamDunc]

Its no good digging a French Drain (open trench) if the water has nowhere to go. You need an outlet to lower land or a soakaway.

Would it not be better to have a 'French Drain' than nothing though as the water would eventually soak into the water table, plus it's better sat in the trench (the lowest point) than on the plot itself is it not?

It does seem to have worked for me and my trench goes down to the clay level (about 15" down).

[Snadger]

Would it not be better to have a 'French Drain' than nothing though as the water would eventually soak into the water table, plus it's better sat in the trench (the lowest point) than on the plot itself is it not?

It does seem to have worked for me and my trench goes down to the clay level (about 15" down).

If something ain't broken don't fix it is my motto, so if it works for you, JamDunc, you stick with it.
All I was thinking is that a trench filled with ground water could actually work as a feeder of water back onto the already wet land unless the land below the plot is lower!

Far better if you have some means of directing it somewhere else in my view!

[rustylady]

I think we need to know what is next to (and below) your allotment Jimmer

[JimmerG]

'Below' my plot is another plot that's lower and just as water logged - that plot backs onto the alloment boundary and onto some housing. Trouble is, I can't see anywhere to drain excess water, but maybe there is a drain at the far end that's blocked. I'd better check.

I'm just wondering weather a drainage ditch would do the job, as it would act as a sump to store the excess water as opposed to it sitting on my beds. I guess a soak away would be the best bet, but I imagine these need to be very deep and full of rubble to work properly.

OR - my other plan, once everything has dried out... next year, is to rotorvate the first 12" of top soil of the flooded area, move all this to one side, then rotorvate right down into the obviously compacted next 12". Then replace the first layer,(plus a load of manure) so I've got a good 2 foot of aerated soil for the water to soak through.

Sound like a plan?

Sounds like hard work to me...!

[Snadger]

Don't suppose raised beds in that area would help would it?...................

[Bigmallly]

I don't envy you Jimmer but the options I see from what you say are:
a) Drain the excess water off somehow & somewhere (Not on the plot below)...
b) Dig dip & put plenty of gravel /grit into the mix to help drainage.
c) As Snadge has mentioned, building a raised bed......which would be my personal choice, even if it's only over the wet area.
d) Make that part of your plot into a natural bog garden with loads of bog plants to attract the beasties.

Good luck with whichever way you decide to go.

[oliveoyl]

A pond... lots of lovely frogs to eat the slugs. Rhubarb and watercress (obviously) like wet, sure other things do as well... you could grow rice

[Nicos]

Is the lottie next to you free/dryer? Maybe you could ask for discount on yours - and do the wildlife thingy bobs- which sound brill...and take on the one next to you - at a discount perhaps- for the veg.
Just a thought!