Surface Water Flood Risk

[Bol87]

We’ve just got the environmental searches back on the house we are buying & it’s come back as ‘high flood risk’ from surface water flooding. All other flood risk are ‘very low’. It’s a 4 year old house (owners are divorcing, hence the relatively early sale of a new build). 3 story, garage & office on the ground floor. Everything else is upstairs.

The house is at the bottom of a hill, so we were aware there would potentially be occasions where water would run down into the estate. But we are so gutted to read it’s considered high risk. The report says 1 in 30 chance of flooding above 1m.

Can anyone help advise on next steps? Can we get a more detailed opinion? Are there additional surveys that should be done?

My other half is ready to walk away. He’s always been ademant we won’t but in a flood risk area as we work in a town that has suffered horrendous damage from flooding of a river. Residents can no longer get insurance & houses are impossible to sell. Now, obviously this is surface water, not a river bursting it’s banks. So it’s clearly not going to be quite so awful. But he says he’ll be worried everytime in rains. Which is all the time. We live in Yorkshire 😫

Any thoughts, advice would be really welcome. Thanks.

I’m very surprised a new estate doesn’t have surface water drainage or amelioration measures in place. The planning authority normally insists on this these days. You would expect to see design details such as planting and green ponds to absorb water run off. What about the road drainage system? It must have one. The evidence of surface water run off coming into the house looks slightly odd to me and the EA should have had an input into the required designs! My DH is an environmental engineer and I know new builds have to have anti flooding schemes designed into them so I would want more questions asked of the planning authority. Or the design info might even be on line at the planning authority.

A new build should have a sustainable urban drainage scheme (suds) to deal with surface water. You should be able to find details on the council planning website. Has it flooded since it was built? I would be wary as a flood can be devastating.

It totally depends on the type of flooding. If it's surface water and it has flooded recently then flood doors may be funded by a local flood amelioration scheme -- check your council website.

Otherwise inexpensive flood gates (that slot across the door) are easy to put in. If you have land, willow whips (away from the foundations) are easy to put in. There are definitely things you can do.

It's important to remember that if it's a flood town, like valley towns in Calderdale, then there will always be a flood ceiling on the price of a house in the river zone, though some canny buyers can do the topography and find bargains inside that. Zone two, surface water risk, usually doesn't hurt the price as much and you can get insurance no problem. If you're worried about insurance, look up the house on flood.re www.floodre.co.uk/can-flood-re-help-me/

Ultimately though, he's saying he would be worried every time it rains. That's not unimportant. Don't buy yourself worries. There are other houses.

Oh also you can look up your house on the historic flood map:

data.catchmentbasedapproach.org/datasets/e73409bf14724c53b350898ff3a752bd_0

The survey you have received most likely has just put the postcode into the EA flood risk database and churned out your report. There are a couple of things to bear in mind

1. The report tells you the flood risk of the location, based on history and flood return models
2. The report wont know what interventions have been put in place in the house itself, nor necessarily the development , like SUDs to mitigate the risk

Si you need to do a bit more due diligence here. You can do this yourself or pay a specialist which you might want to do in order to get an official report to reduce your insurance should you proceed with the purchase. As PP said, all the development interventions should be held in the planning documents, this will include the EA sign off of said plans. You also want to know if there has been heavy rain incidents in the time since built, ie has it been put to the test?

We bought a house that was in an area that could flood, but our house was higher up and couldn't flood. We had it on the market and, of course, there were the worst floods for 50 years. Ours was untouched, but neighbours had to leave their homes for up to a year for repairs. Our postcode was blacklisted for insurance and we couldn't sell. We got the environment agency to come and to a survey and provide us with paperwork for insurers. We eventually sold after nearly two years. It was very stressful and my next door neighbour who didn't get any flooding had her house insurance go up from £300 a year to £1300. I'd be very wary and ask about the cost of insurance etc.

@lojoko - we work near Hebden. The last two floods were just heartbreaking. We aren’t buying in Calderdale though. The house is nowhere near a river, hence why we didn’t think there’d be any high risk flood issues .. we aren’t aware of any flooding but we will now obviously check.

Thanks so much for all this info, it’s really helpful. We’ll have a discussion about how to move forwards..

Surface water flooding is mostly volume of road surface to drainage. Is your house slightly raised up from the road. Does it have a paved driveway? Is there drainage nearby? How much green space/ trees etc. It’s basically how much water can soak away quickly in a storm if it doesn’t soak away it creates flooding on hard surfaces.

Yes, I almost wrote "like Hebden"! (I know Hebden well.)

Yes. Surface water flooding is not the same as rivers flooding. (I simply could not remember SUDS earlier this morning). DH's firm do a lot of work for developers on this because planning authorites and the EA are pretty demanding now.

Do further investigation with the LA Planning department records to see what scheme was put in place to stop surface water flooding. This will have been a requirement and is a Big Thing now in estate design. Have a drive around in pouring rain! Plenty coming up. It is fairly unusual for surface water to flood a house on a new estate for precisely the reasons outlined. You do want to see green ponds to hold back water, (preferably planted with reed beds), green spaces and trees. You want less hard standing and more green areas. You need to check that the water is prevented from getting to the houses at the bottom of the hill by schemes higher up on the estate.

It’s a really small estate. Just 16 houses. Built on the site of an old railway station that stopped operating in 1950! So there’s no ponds for sure.. all the houses have strips of grass out front but that’s about it. We’ve sourced some planning apps & there were def several drainage conditions they had to meet so that’s a positive I suppose..

Another question - we were just having a basic valuation done as the house is so new. Is flood assessment covered in any surveys we could pay for or would it be wise to pay for a specific flood risk survey?

Ps. Thank you again, this really is all v helpful!

Do you know who the builders/developers were? They would have records of what was required. They might have employed Environmental Engineers to design or advise on what was required. You might need to pay for this info, but you might not. Also flood frisk is not a terribly accurate prediction. One of the reasons for this, is that going back 100 years, you might find one flood record. In the last 5 years you might have 2 out of 5 years flooding. So, as this is surface water, your best bet is to ask what has been done to help with this problem.

The station was built on where I used to live! It never flooded.

I know the building company, we’ve emailed them for some more information. We’ve poured over the planning permission drainage info on the council site & it seems robust enough although obviously I’m no expert. It’s a ‘free draining’ site with an emergency flood route system & soakaway manholes. 🤷🏼‍♀️

We’ve dug down & only 3 of 16 houses are classed as high risk. The others (including 3 across a small road & at the exact same level) are deemed very low risk. Which I find a bit baffling. I’ve also ascertained from the vendors that in 2019, a small amount of water came into their garage during Storm Dennis. They say there was no flooding as such (they clarify this as no pools of standing water bar puddles), rather just a lot of rain being hammered against their garage in strong winds. The owners claimed on NBHC insurance & extra drainage was fitted outside all the garages on the estate. No water entered the main house.

We’ve gone back to our solicitor with more questions.. we think we’ll maybe get a flood survey done to dig down why 3 properties are so different in risk to others. Could it possibly be that the work carried out in 2019 by NHBC was reported to the council & that’s why 3 specific houses are at risk? The houses across the road don’t have garages & so weren’t affected/were not part of the claim? 🤔

The 3 houses could have had specific flood surveys conducted.
They could be very slightly different height.
They could have claimed for overflowing guttering or other trivialities.

There is an estate being built near us that is very dodgy. It will flood due to surface water flowing through it as it’s on the middle of a hill. The water will end up on the main road at the bottom. No one is claiming responsibility. The Environment Agency don’t deal with surface water apparently. The district and county council are blaming each other.
I keep telling them that we have never flooded as I reckon they will try and divert the water our way. Which is illegal. Legally the new estate has to accept water from above and not make the situation worse for those below although those below have to accept the same volume they always did. It that makes sense!