How to stop the garden from flooding during the winter

[Narmelleth]

(Re-posting from Gardening)

I could really use some advice as this is really getting me down.

The garden is a mess to the point I refuse to step foot outside. I want to redo the whole thing so I can finally enjoy it.

Only issue is that in the winter months for the last two years the garden started getting flooded. This is not a bit of water, a few puddles here and there.
This is properly knee deep water at its worse, ankle deep at the best case.

The garden backs up at private woodland and from what i have seen lots of the water enters from there when it rains.

Before I bother redoing the garden, is there anything I can do to sort the flooding?
Is blocking the back entrance with a barrier of sorts realistic?
Trying to raise the garden level so we are higher than the woods? Is that feasible?
I don't think rain gardens and planting a few water loving plants are going to cut it. There is so much water.

I don't want to spend money and energy fixing the garden only for the flooding to put me back to zero.

How would you tackle this?

(Someone said to talk to neighbours in the previous thread. DH did and apparently all the properties backing to the woods had a gully build but previous owners in order to expand their gardens extended the gardens and covered it?? Seems covering it is causing the flooding now, but I am unsure about all this as H is not the best information sharer and he is all doom and gloom right now and that nothing can be done with the gully to fix the issue. Or in general we just have to live with it...)

Who owns the woodland?
What written observations have you made regarding winter water flow?
what written observations have you made regarding your own topography and water behaviour? What type of soil do you have? Lots of water in clay would be a real problem.

I think that this will take time to sort out if you don’t have this information already available. So, use this summer to clear your garden, investigate what infrastructure, including fencing, walls - everything- you already have, dig test pits to clarify your soil structure. Make notes and take photos. Then in winter, you can see what happens. Make notes, take photos and draw diagrams.

Try and get around the back to look at the woodland. Take a walking stick for poking around. Try and see what the neighbours have in the way of infrastructure, too. Do they still have their flood mitigation drains and is it only yours that has been filled in? If the drainage was one long trench, where are you placed along that trench? Who was responsible for digging the trench in the first place? Check your house deeds and get out with a tape measure. If your house is in a fairly recent development, check the developer’s plans. (In fact, do this bit first).

If you haven’t got clear observations of cause (rainfall) and effect (water flow), you won’t get far, I wouldn’t think. Talk the council planning department about responsibility for water on your property (reading on Mumsnet says that property owners do have some responsibility for water movement).

But, further from my point above, if the developer had put in flood mitigation measures and a house owner had altered them, then perhaps it may not be much of a stretch to reinstate them.

You need the hydrology data to see where the waterways are. Then find if they are blocked, then speak to the riparian owners about clearance. It's not a quick fix.

If you have the space, dig a big ditch/pond where the worst of the flooding is to contain it, but you should probably get specialist help with this. We have the same kind of issue and 15 years ago, the cost to sort it was £25k. We just accept that in a wet winter, the bottom of the garden floods and is a swamp and don't use it. We are on heavy clay.

That’s what I didn’t think of - maps!

Beechgrove Garden BBC IPlayer is resculpting an area of garden that floods. It might be worth looking at Episodes 5 & 6 to see if this would offer a solution to you.

You need the gully re-instated. Do that before you do anything else.

Thank you for your reply.

To answer some questions:

According to the neighbour H was talking to (lets call him Tom) the woodland is owned privately.

No written observations which of course I am regretting now but from memory water would flow in from the back gate (so from the woodland) and into my garden and other neighbour's garden (so the other neighbour -not Tom- is getting flooded by the woodland as well). I think the neighbour might be higher than us as their water doesn't seem to be as high as ours so I am wondering if their water also comes to us. Once the garden is flooded if it stops raining in a couple of days it drains away (if it has been knee high, if water is lower then quicker).

Soil type I am unsure but going by the Internet our area is 'loamy and clayey'. How accurate is that I don't know but clayey looks about right...

The house was build in the '70s. I have looked at the title plans and there is one solid line labelled as 'drain' that is going through at the end of all the gardens. According to Tom everyone in the row of houses extended their gardens over that drain. Parallel of that drain there is a dotted line which is labelled as 'boundaries' so I am guessing everyone didn't want to waste that extra bit of land between the drain and the boundaries so they pushed their garden to that boundary, so Tom's story kind of checks out.

There are 14 gardens next to each other, all backing the woods. We are in the middle.
Tom whose garden is at the other side of us doesn't really get flooded, just a bit waterlogged. Apparently he has decking over his and he can hear the water flowing through under the decking. So looks like his gully is doing the job. Although, I am unsure how if we are all connected to one long drain.

Could we do that just for our garden?
H said that because we are all connected to one long drain/gully/whatever that everyone will have to dig their gardens to find where the blockage is.

Thank you I will have a look.

Is there a watercourse in the woods (river/stream) or is it all just surface runoff?

Are there steep slopes involved?

It sounds as though you might have to employ a drainage engineer to work out what is actually going on a come up with some solutions.

So, the flooding problem was known, provision was made to mitigate the problem, people over the years have mucked about with it and now it doesn’t work.

Yes, specialist advice is going to be needed. This is more than just needing a few willows planted.

Yikes, 25k! I dread to think nowday prices...

The whole street must be having issues. I’d be knocking all the doors downhill from me at least and speaking to them and subsequently perhaps calling a meeting or something to see what could be done. It could be that the gully could be reinstated or something. I wonder if the gardens being extended was done legally ie they bought the land or what. If they just took it over they may not want to discuss the issue.

I wonder if there is anything in your deeds that would help? The deeds to my place include a covenant that allow me access to the wood opposite to maintain waterways affecting my property.

So I thought this was surface runoff but looking at hydrology maps there is a small river/stream at the one end of the row of houses. Around 0.1 miles away from our house.
However, looking at google maps it looks like the river branches off towards the houses. The end of that branch is 56 yds away from us.

I am guessing that this is contributing to the issue.

Well last year, at the end of the row of houses the water was spilling out on the street from the woods. Those woods were more like a lake. But I think the councils solution was to put more drains on the roads. We live in a village and to be fair lots of streets and pavements (unconnected to the woods) had turned into ponds.

In regards to the neighbours, one of our neighbours is flooding as well. The other neighbour just a bit waterlogged. Unsure how the rest of them are faring. I will have to knock on some doors.

I think it was done legally, as it seems the boundaries were after the drain? I might need to quiz Tom as all this was done way before us.

So according to neighbour Tom we will need to ask permission from the woodland owner if we need ti do any modifications outside our boundaries.

I have looked at the deeds and I can't see anything about the woods.

nothing useful to add but protect those woods with all your might if a developer comes sniffing. Imagine how much worse it would be without them. They will be absorbing and slowing so much water down.

Infuriating isn't it? When we moved it was fine, no problems at all. Only the last two years it suddenly became an issue. I don't know if it's the increase in heavy rains or something somewhere got blocked and it's now affecting the water flow.

They are privately owned and I have the suspicion that they were bought a long time ago with the intention of developing but for whatever reason they have been left untouched.

@Narmelleth Yes we were 😳 needless to say it didn't get done! Luckily there's not a lot of daylight hours in winter so we just pretend it's not there. It's nice in spring though as we get mallard ducks come to visit. We've had ducklings before which was sweet.

Before you do anything other than finding the drain / blockage - have you tried the free sand bags to see if it makes a difference? This would be a cheap way of seeing if the back gate is the issue.

If the garden is knee deep, is your house higher?

We haven't tried sand bags but I was thinking about trying to barricade the back gate/fence with something.

The house is higher yes. You open the back door and there is decking, then steps down to the garden. I hope it never gets so bad to the point it reaches the house level. Properly screwed then.

@Narmelleth

Could it be worth trying something like this, in front of the original drainage (closer to your house)

Or would you lose too much garden?

It is a smallish garden so we would lose space.
I am wondering if it's possible to uncover the old drain/gully and see if anything could be done with our section.

There is a small deck platform at one corner at the end of the garden. I am hoping that previous owner maybe did what neighbour Tom did and instead of covering over with soil they decked over it. Might be easier to locate if that's the case.

I know I am heavily clutching at straws here.

Search flood authority for your local authority area, they will have some resources on their website so you can find out what else is going on locally and you can get in touch with them. Responsibility for waterways sits under a number of different authorities depending on what it is.

There are a whole lot of resources about what individual households can do on this website https://floodmary.com/.