Making Sense of "Flood Risk due to Surface Water" (See Map)

dancing_star

Slithery wrote: »

In my opinion the flood search results are often useless. The last property my mum bought was classified high risk because there was a stream 100m away, never mind the fact that it was 30m lower than the house.

I had that with my last property.

As well as the building being several metres above the stream the flat was on the second floor.

(yeah I know the building insurance blah blah blah, but it made me laugh)

kaych

lovehols wrote: »

How do I check the likelihood, that is the website I got the map off but I can't see how to check how likely it is.

At the top, slide the option to 'detailed view' and you will see there are more options under surface water flood risk. In there you will see the high, medium and low risk on the potential depth and velocity.

High risk means this is the situation that is most likely to happen in terms of surface water flood risk and you will see how severe your site may be affected by surface water flooding.

The 'low risk' is always more severe, as this refers to more extreme rainfalls and storms which has the least probability (low) of happening. so basically the worse case scenario. I would say this is rarer but it is not impossible to happen (as storms are getting more frequent and severe). So it would be good to know so you are prepared for this if necessary and the map gives you an estimate of the potential flood depth and velocity - not the most accurate but the best data you will get without doing a site specific assessment.

lovehols

kaych wrote: »

At the top, slide the option to 'detailed view' and you will see there are more options under surface water flood risk. In there you will see the high, medium and low risk on the potential depth and velocity.

High risk means this is the situation that is most likely to happen in terms of surface water flood risk and you will see how severe your site may be affected by surface water flooding.

The 'low risk' is always more severe, as this refers to more extreme rainfalls and storms which has the least probability (low) of happening. so basically the worse case scenario. I would say this is rarer but it is not impossible to happen (as storms are getting more frequent and severe). So it would be good to know so you are prepared for this if necessary and the map gives you an estimate of the potential flood depth and velocity - not the most accurate but the best data you will get without doing a site specific assessment.

Thank you, I got some more detailed information, I'd missed the drop down boxes. This is all the information relevant to the property:

Flood Risk - Extent of Flooding Surface Area

Map shows high and medium risk (this is the map I posted)

I've also got the other information;

High risk: Depth (millimetres)
300 to 900mm
Below 300mm

High risk: Velocity
Over 0.25 m/s
Less than 0.25 m/s

DCFC79

Slithery wrote: »

And there's me trying to figure out why your food is at risk.

Lol I was wondering the same.

lovehols wrote: »

Oh my god I didn't notice that!!! I can't seem to edit it either.

Im sure you can edit it if you choose the " Go advanced" option.

lovehols

DCFC79 wrote: »

Lol I was wondering the same.



Im sure you can edit it if you choose the " Go advanced" option.

Thanks, just managed to do it on the advanced option!

EachPenny

Do you know what is on the other side of the railway embankment where the map shows a large area of dark blue?

At a guess a computer model has determined this area might be subject to flooding to height 'x' and then computed all the areas within a countour line at the same level as 'x'.

If you imagine the railway embankment was not there, then the area of dark blue just about the cross-hairs then becomes the 'head' of one very large 'lake'. To me that suggests a computer model has identified the land either side of the embankment as being the same level and therefore equally at risk of flooding.

However, in practice the embankment might be acting like a dam protecting the canal side of the railway embankment against flooding.

Flood modelling is not a precise activity, it has to make assumptions about levels of water and the hydrological connectivity between different areas of land. For example if there was a culvert under the railway embankment then it wouldn't be an effective dam between the two areas. So the modelling usually works on a worst case basis and assumes connections or links without necessarily having evidence one exists.

If you don't already know then I would try to find out what is on the other side of the embankment and whether that area is actually known to flood.

lovehols

EachPenny wrote: »

Do you know what is on the other side of the railway embankment where the map shows a large area of dark blue?

At a guess a computer model has determined this area might be subject to flooding to height 'x' and then computed all the areas within a countour line at the same level as 'x'.

If you imagine the railway embankment was not there, then the area of dark blue just about the cross-hairs then becomes the 'head' of one very large 'lake'. To me that suggests a computer model has identified the land either side of the embankment as being the same level and therefore equally at risk of flooding.

However, in practice the embankment might be acting like a dam protecting the canal side of the railway embankment against flooding.

Flood modelling is not a precise activity, it has to make assumptions about levels of water and the hydrological connectivity between different areas of land. For example if there was a culvert under the railway embankment then it wouldn't be an effective dam between the two areas. So the modelling usually works on a worst case basis and assumes connections or links without necessarily having evidence one exists.

If you don't already know then I would try to find out what is on the other side of the embankment and whether that area is actually known to flood.

Yes, we have extensive walked the area. Once you go over the canal bridge the entrance to the property is on the left down a small private drive. If you carry straight on under the railway bridge there is a large farm around a quarter mile or so at the end, nothing else. We have, from the property climbed up the embankment to the old railway and bridge (very steep) and then the other side descended it, agin very steep down into the farmers field. All this area is fields so yes you are basically right. There is fields, the embankment and then the property the other side of the embankment which I guess would be on the same level as the fields but the embankment is basically in between.

Here is a picture looking towards the farm under the bridge. All three times we have viewed the property have been after prolonged periods of rain, well actually one of them was after heavy snow so we've never seen it dry, we've definitely seen it at its worst!

https://flic.kr/p/23F8Ce6

lovehols

Some good news, Environment Agency have no record of any flooding and I've chatted to LV and AXA today (the two cheapest insurance quotes) and insurance is not an issue, declaring the canal and trees and no history of flooding.

I then confirmed it again with LV on an online chat:

"We will be aware how close you are to water by your postcode this will be taken into consideration already when we quote you".

One less thing to worry about and I'm happy with the responses. Thank you everyone for the replies.

Just the ongoing septic tank issues to sort now!