Does flood barrier work?

tim_london

Looking at a new build, built on floodplain - technically zone 2, but it is so close to zone 3 let us just call it that.  River stream is about 100m away.

• Full EA Exception Test done before build - the raised the finished floor level to cater for worse case + global warming.  However we all know it's not going to be enough for really big flood events (once in 10 years).
• The property base is piling + concrete, so there are no air bricks around.  There are weeping holes slightly higher up for wall cavity though
• Sewage/Foul water is on separate pipe system and goes to a Thames water pump.  Surface water drain goes to the river with various SuDs on site to keep water in.
• Whole development including garden has geo-textile base as a mitigation against groundwater risk - full independent report and advise was done and is part of planning permission requirement.
• The garden is sloped towards the river and acts as a 'floodplain'.  EA advises via planning permission that water can freely come into the garden and fence has to be 'hit and miss'.

Would you consider it if you had flood barrier to add extra protection to doors?  I've not seen anyone say flood barrier work well, ever...

ProDave

No. Not unless there were absolutely no other non risk houses for sale, or it was VERY cheap.

oldbikebloke

what do you mean by flood "barrier"?
if you actually mean flood door, then yes they do work
but they are very expensive and need proper installation obviously, these were fitted on an estate near me, the cost of replacing all external doors was several thousand £ for each property
https://www.stormguardfloodplan.com/flood-doors/

AdrianC

I presume it's all very flat...? Even a very slight gradient over 100m is a LOT of volume of water.

tim_london

oldbikebloke said:

what do you mean by flood "barrier"?
if you actually mean flood door, then yes they do work
but they are very expensive and need proper installation obviously, these were fitted on an estate near me, the cost of replacing all external doors was several thousand £ for each property
https://www.stormguardfloodplan.com/flood-doors/

I was thinking this type: https://stormguardfloodplan.com/flood-barrier/.  And yes several thousand £ to install which is quite a lot but does feel worthwhile if that prevents water from getting in.  Just that I see a lot of websites and even govt papers recommending it, but I have not seen a real person say on a forum that it saved them from flood related damage and a claim to insurance.

AdrianC said:

I presume it's all very flat...? Even a very slight gradient over 100m is a LOT of volume of water.

Kind of.  The garden is very small.  For example in February after double trouble storm Dennis and Ciara the river bank was breached and the water was in the garden.  It was about 10m away from door and about 25cm in height to reach the patio door - floor level. So it is kind of proven to be able to deal with a bad storm but probably not enough for a very bad one.

AdrianC

tim_london said:
For example in February after double trouble storm Dennis and Ciara the river bank was breached and the water was in the garden.  It was about 10m away from door and about 25cm in height to reach the patio door - floor level. So it is kind of proven to be able to deal with a bad storm but probably not enough for a very bad one.

I think you've answered your own question there, don't you?

tim_london

AdrianC said:

tim_london said:
For example in February after double trouble storm Dennis and Ciara the river bank was breached and the water was in the garden.  It was about 10m away from door and about 25cm in height to reach the patio door - floor level. So it is kind of proven to be able to deal with a bad storm but probably not enough for a very bad one.

I think you've answered your own question there, don't you?

I don't, that's why I'm asking.  I see this kind of answer a lot but it doesn't give me the 'why'.  

I grew up in a flat so I've never seen the devastation of flood damage.  Most of the comment I've seen about flood damage is water in-between wooden flooring which causes the '1 year away from home to let things dry up and fix' issue.

Here is a new build with flood risk in mind, full EA assessment done and some features built in place to prevent or minimise flood damage when a very bad one occur maybe once every 10-20 years.  Isn't it a case of keeping the water out from doors, is it really that impossible?

oldbikebloke

tim_london said:

oldbikebloke said:

what do you mean by flood "barrier"?
if you actually mean flood door, then yes they do work
but they are very expensive and need proper installation obviously, these were fitted on an estate near me, the cost of replacing all external doors was several thousand £ for each property
https://www.stormguardfloodplan.com/flood-doors/

I was thinking this type: https://stormguardfloodplan.com/flood-barrier/.  And yes several thousand £ to install which is quite a lot but does feel worthwhile if that prevents water from getting in.  Just that I see a lot of websites and even govt papers recommending it, but I have not seen a real person say on a forum that it saved them from flood related damage and a claim to insurance.

OK, if you are meaning that same supplier, then as they say on the website, they will do a survey and recommend either the door or the barrier 
the drawback of the barrier is obvious - you need accurate forewarning so you can place it. The door operates all the time of course, hence is more expensive as it has to be that much better. 

It has not flooded since the estate had the doors done, so can't personally  say they work, but I know I'd get them if I could afford them (the estate houses were given flood "resilience" funding). Instead I have made my own barrier, but have little faith in it as placing it will be time consuming and unlikely to happen when I'm there able to do it.

Vectis

probably not enough for a very bad one.

But, you HAVE answered your own question. Why would you even consider purchasing a property which you admit yourself is liable to flooding once every 10 years or so? Why would you take the risk, even if you haven't experienced the after-effects of a flood before?

Are there no other suitable houses which aren't built on a flood plain?

AdrianC

tim_london said:

AdrianC said:

tim_london said:
For example in February after double trouble storm Dennis and Ciara the river bank was breached and the water was in the garden.  It was about 10m away from door and about 25cm in height to reach the patio door - floor level. So it is kind of proven to be able to deal with a bad storm but probably not enough for a very bad one.

I think you've answered your own question there, don't you?

I don't, that's why I'm asking.  I see this kind of answer a lot but it doesn't give me the 'why'.  

I grew up in a flat so I've never seen the devastation of flood damage.  Most of the comment I've seen about flood damage is water in-between wooden flooring which causes the '1 year away from home to let things dry up and fix' issue.

Here is a new build with flood risk in mind, full EA assessment done and some features built in place to prevent or minimise flood damage when a very bad one occur maybe once every 10-20 years.  Isn't it a case of keeping the water out from doors, is it really that impossible?

Perhaps I misunderstood slightly. I thought you were meaning barriers to keep the water out of the development itself - rather than simply door barriers to keep it out of the property.
This sort of thing?

The big issue with flooding is that it isn't just river water. Sewer levels rise, too, and they all get mixed in together...

The door barriers are going to be as good as their fitting and use, and as good as the hermetic sealing of the rest of the property. It won't take much to get a leak, especially as they age and their seals start to perish. There is a HECK of a lot of weight and force behind floodwater...

In Dennis, the lane by my gate flooded, because the drains for the stream overflow got blocked. Not much - about welly-depth at the deepest, over an area of probably 10m x 10m. Even so, do the maths, and that's 50,000 litres of water, 50 tons of water. When I got the drains cleared, that all emptied in a couple of minutes - and it wasn't a trivial job to stay standing in it.

The river under the bridge in the middle of my nearest city was six metres deeper than normal. In my nearest town, several cars floated downstream from a carpark.

No, I wouldn't buy a property that was relying on me correctly fitting a bit of bent tin into a doorway. As you say, there's an expectation that the river will flood the garden. And, presumably, the car parking. And they simply recognise they can't stop that. Is there any communal development area maintained by service charges...?

Davesnave

Vectis said:

probably not enough for a very bad one.

But, you HAVE answered your own question. Why would you even consider purchasing a property which you admit yourself is liable to flooding once every 10 years or so?

It probably comes down to price.

About 12 years ago, we were looking in the West Country generally and noticed there were properties of the type we wanted on the Somerset Levels at a just-about affordable price. However, we've known the Levels for many years so we decided not to take the risk. Winter 2014 proved we were right.