Found a House - High Risk Surface Water.

[Chris344]

I am in the early stages of purchasing a property which is currently identified as being at high risk of surface water flooding on the future flood risk map on the Gov Environment website. There are no rivers or seas in close proximity, and I understand that flood risk assessments are generally based on geographic and topographic data rather than the physical condition of the land (e.g., whether it is concreted or grassed).

The current owners have installed a full shingle driveway, ACO drains at the front of the property that drain into the main sewer, and a block lip at the top of the drive. They have confirmed that, in their seven years of ownership, they have not experienced any surface water flooding issues, even before these modifications were made.

I posted on the local community group, and someone two doors down responded with: “they used to get surface water pooling on their drive but not since they’ve had the drainage and shingle drive installed (like you said).”

Here's the map, would you be concerned?

 

[fastwunz]

Personally no - most of London is at risk of surface water flooding because evryone concretes over everything. The fact it’s not next to a water course would satisfy me enough if I liked property. I would make damn sure it’s never flooded in the past before I proceed though.

 

[Hagar]

Is the property in a dip?

Surface water often applies to ground water that can rise above ground level through being surcharged by water at a higher level nearby. The ground may be wet quite close to the surface.

Only surmising and I may be quite wrong.

 

[arknor]

I'd probably check the rainfall data for the last 7 years, then compare it with years before that.

in their seven years of ownership, they have not experienced any surface water flooding issues, even before these modifications were made

isn't that kinda contradicted by

“they used to get surface water pooling on their drive but not since they’ve had the drainage and shingle drive installed .”

and the fact they claim they had no flooding issues, but still made modifications anyway..

kinda hints that they did have issues, even if it didn't actually flood into the property itself.

I wonder if theres nice marsh like conditions after rainfall in the summer, loads of mosquitos and midgies breeding around the house and in the drainage


Have you checked google street view? you can change it to show older photos, sometimes they go back every year to around 2011 or so.
depends how often a google car drove past

 

[Chris344]

Is the property in a dip?

Surface water often applies to ground water that can rise above ground level through being surcharged by water at a higher level nearby. The ground may be wet quite close to the surface.

Only surmising and I may be quite wrong.

The side of the road that the house is on slopes down, the houses on the other side of the road are raised and they are classed as low risk for surface water.

 

[Chris344]

Personally no - most of London is at risk of surface water flooding because evryone concretes over everything. The fact it’s not next to a water course would satisfy me enough if I liked property. I would make damn sure it’s never flooded in the past before I proceed though.

A friend of mine is a senior insurance underwriter and has checked the house on his system, as per his records, the house has no recorded flood claims. He said they wouldn't impose any special terms and the insurance quote I did came back around £250 for building and contents.

He did say the houses behind have had surface water issues in their gardens mostly, as it continues to slope that way but they are 200-300ft away.

 

[Chris344]

I'd probably check the rainfall data for the last 7 years, then compare it with years before that.


isn't that kinda contradicted by


and the fact they claim they had no flooding issues, but still made modifications anyway..

kinda hints that they did have issues, even if it didn't actually flood into the property itself.

I wonder if theres nice marsh like conditions after rainfall in the summer, loads of mosquitos and midgies breeding around the house and in the drainage


Have you checked google street view? you can change it to show older photos, sometimes they go back every year to around 2011 or so.
depends how often a google car drove past

That's what makes me suspicious, they've had no issues but spent money on preventative measure - maybe in readiness to sell? The house was fully extended and modernised in 2020, with the drive being a recent change. The Google Street View image shows the old tarmac/grass drive just last year.

 

[arknor]

The Google Street View image shows the old tarmac/grass drive just last year.

so they wouldn't even really know yet if their preventative measures even work?

maybe extending the house is what caused the issues.

seems like they did the drainage purely to sell the house tbh....

 

[Chris344]

so they wouldn't even really know yet if their preventative measures even work?

maybe extending the house is what caused the issues.

seems like they did the drainage purely to sell the house tbh....

The neighbour in the group said water used to pool on the old drive, but not since they changed to the shingle drive way. Which is all well and good, but how well will it perform if we get that 1 in a 100 year storm.

Agreed, they knew it could be a hard push with the surface water risk and did the drive/drain works to help with the sale.

 

[Chris344]

I have been quoted £3300 for a full flood risk assessment, which includes:

Key tasks will include:
Site reconnaissance as required;
Request relevant flood information and data from the EA, including details about the level of flood protection, modelled flood levels and extents, and historical records of flooding;
Review the local Strategic Flood Risk Assessment (SFRA) and any relevant flood modelling and historical records contained within (if available);
Use of available flood modelling data to establish the annual probability of the site flooding, and the building being inundated (if possible using existing modelling);
Use of LiDAR remotely sensed topographic data (or topographic survey information, if available) to derive likely flood depths on site during a range of different flood events;
Assessment of likely groundwater flood risk;
Review of any relevant planning applications with regard to flooding;
Outline recommendations for work that could be undertaken to mitigate the risk and impact of flooding on site;
Production of a flood response and evacuation plan for future occupants of the building.

Delivery will include:
Production of a final written report to;
provide you with information about the risk of flooding to help inform you of the flood risk to the property;
be presented to a future insurance company to provide them with a high level of information about the risk of flooding;
be presented to a future purchaser of the building to provide them with a high level of information about the risk of flooding;
A flood response and evacuation plan for future occupants of the building;
Outline recommendations for additional work, to include outline recommendations for property level protection.

This is the wider flood risk map:

 

[arknor]

have the owners never had a flood risk assessment themselves? surely they moved in knowing there was a flood risk listed?

maybe they don't want to disclose it.

 

[radderfire]

You say there are no rivers (or seas!) in close proximity, but what do all the blue markings of water on the maps represent?

 

[Chris344]

I've just had an environment flood search back, typically, the same as a solicitor would order which is showing low risk - I'm a bit confused.

 

[Chris344]

You say there are no rivers (or seas!) in close proximity, but what do all the blue markings of water on the maps represent?

Surface/drain water

 

[radderfire]

Surface/drain water

So, is this standing water, like puddles/ponds of water? If so, are some very close to the house?

If there were, I have to say it would put me off the house. Personally, I would only be looking at houses that had no hint of the possibility of being flooded, as I can think of few things worse.

 

[Chris344]

So, is this standing water, like puddles/ponds of water? If so, are some very close to the house?

If there were, I have to say it would put me off the house. Personally, I would only be looking at houses that had no hint of the possibility of being flooded, as I can think of few things worse.

Correct, it's standing water that could pool in the gardens of the houses behind (slopes downwards) and some street level standing water.

 

[Chris344]

I've raised a query with the Environment Agency.

 

[jpaul]

How much would house insurance be ? for it and neigbhouring properties as an indication of local risk.
(ok earlier thread on flooding was also yours https://forums.overclockers.co.uk/t...ea-but-surrounded-by-flood-zone-2-3.18986007/ where made similar point)

Personally, you can access a lot of the authorities flood risk data and modelling.

The drive renewal could be a red herring did they used to have a undulating piece of tarmac, say.

 

[Chris344]

How much would house insurance be ? for it and neigbhouring properties as an indication of local risk.
(ok earlier thread on flooding was also yours https://forums.overclockers.co.uk/t...ea-but-surrounded-by-flood-zone-2-3.18986007/ where made similar point)

Personally, you can access a lot of the authorities flood risk data and modelling.

The drive renewal could be a red herring did they used to have an undulating piece of tarmac, say.

Insurance quote was £250. We current pay £7-800 on our current house.

How can I access the modelling?

It could potentially well be. They bought the house in 2018 and extended it but left the drive until recently. They also recently installed an oak porch so you could be right. The old drive was just half tarmac and grass.

 

[Chris344]

I've just had an environment flood search back, typically, the same as a solicitor would order which is showing low risk - I'm a bit confused.

I questioned why the Environmental Agency’s website indicated the property was at high risk of surface water flooding, while the environmental report stated it was low risk. This was their response:

“The flood report that you have received contains the very latest data and was compiled today. Please use the online viewer linked within the report to see the proximity of any risk areas within the locality—some are within 5m of the title boundary, while others are over 40m away. These reports are highly granular and property-specific to ensure that lenders can rely on their content. Landmark is one of the largest suppliers of environmental data to the sector across the UK.

You will also see references to JBA Risk Management, who provide insurability data. I can assure you there is nothing to gain by providing you with a report showing minimal risk, as Landmark would not stand to gain anything from it.”

Based on this, it appears that the risk from surface water is indeed low. This is the same report a solicitor would request during conveyancing and the report a lender would rely on over the EA’s site.