KimB Posted October 16, 2019 Share Posted October 16, 2019 (edited) We are just in the pre planning process stage for building a new build chalet style bungalow on some land at my parents. We knew it might be tricky as knew when we investigated that the land in question in on archeological land, plus half in flood zone 3, at the other bit in no flood zone. The land has never been flooded in over thirty years of my parents living there. We have had one planning meeting in which we were told by planning officers that we would categorically be refused planning unless we sought the Environmental Agency to come out and access the land and complete tests to to be able to proceed. We have assigned a Architect and he seems fairly hopeful about this build. With the EA fees to do this coming in at £100 a hour, we wanted to seek any advice if someone has done this and succeeded with building a new build (not an extension) on flood zone 3? The archeological side of things we aren't to worried on as we know the English Heritage with want to oversee the foundations. Any advice if anyone been through a similar build, was it successful? Floodzone.pdf Edited October 17, 2019 by KimB attached PDF Link to comment Share on other sites More sharing options...
ProDave Posted October 16, 2019 Share Posted October 16, 2019 The builder that built our frame tried to get planning to build a new house in his large garden next to a river. In spite of his garden never having flooded in living memory and the new proposed house being at least a metre higher than the existing one, it was refused. Link to comment Share on other sites More sharing options...
PeterW Posted October 16, 2019 Share Posted October 16, 2019 Welcome ! Where in the UK are you..? That makes a difference.... You can build on F3 ground, just need to be clever with design and make the flow of water around the building acceptable to EA. A decent hydrologist should be able to help with that. Link to comment Share on other sites More sharing options...
KimB Posted October 16, 2019 Author Share Posted October 16, 2019 24 minutes ago, PeterW said: Welcome ! Where in the UK are you..? That makes a difference.... You can build on F3 ground, just need to be clever with design and make the flow of water around the building acceptable to EA. A decent hydrologist should be able to help with that. Link to comment Share on other sites More sharing options...
KimB Posted October 16, 2019 Author Share Posted October 16, 2019 Thank you, and thank you for advice on hydrologist. I'm in Chertsey in Surrey, under Runnymead Council. Link to comment Share on other sites More sharing options...
KimB Posted October 16, 2019 Author Share Posted October 16, 2019 30 minutes ago, ProDave said: The builder that built our frame tried to get planning to build a new house in his large garden next to a river. In spite of his garden never having flooded in living memory and the new proposed house being at least a metre higher than the existing one, it was refused. Oh no....sorry to hear that! Link to comment Share on other sites More sharing options...
colin7777 Posted October 16, 2019 Share Posted October 16, 2019 (edited) You can build on F3 ground, just need to be clever with design and make the flow of water around the building acceptable to EA. A decent hydrologist should be able to help with that. Not true in my experience, I thought just placing a building on piles would eliminate the planning problem but rules are rules and common sense doesn't come into play. Edited October 16, 2019 by colin7777 Link to comment Share on other sites More sharing options...
KimB Posted October 16, 2019 Author Share Posted October 16, 2019 We have been told we are not allowed to build up (stilts etc) as not in keeping with the rest of the houses on the road. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2019 Share Posted October 16, 2019 A part of our plot is in the flood risk zone. The chap over the road tried to get PP for some of his land and spent ~£4K on a flood risk assessment, to no avail. I was asked to provide a similar flood risk assessment by the EA, as a part of the initial planning consultation. I didn't want to spend £4k, so I rang the EA and asked them what they wanted. A helpful lady there said they had the flood risk maps for the area, and she emailed them to me. I overlaid these on to our plot, added the house, drive and garage locations and asked the EA for advice. They came back with a recommended finished floor level for the house, garage and drive parking area. I wrote a three page flood risk assessment myself, giving the positions and levels. I ended up with planning consent with a condition imposed by the EA as to the finished floor/parking levels, which were the same as those I'd been given informally. Link to comment Share on other sites More sharing options...
KimB Posted October 16, 2019 Author Share Posted October 16, 2019 Thank you for this info...interesting!! Unfortunately we didn't get a helpful lady on the phone, but good to hear your experience on this. Link to comment Share on other sites More sharing options...
PeterW Posted October 16, 2019 Share Posted October 16, 2019 43 minutes ago, colin7777 said: . Not true in my experience, I thought just placing a building on piles would eliminate the planning problem but rules are rules and common sense doesn't come into play. OK - did you take a standard build and just want to go with raised piles and use them as the free flow area ..? The issue is that piles create both a free flow area and an obstruction. They can trap debris in the gaps and cause bigger issues hence why you need hydrology to help. You can get away with reinforced banks and flood basins if managed carefully. 1 Link to comment Share on other sites More sharing options...
jamieled Posted October 16, 2019 Share Posted October 16, 2019 Forget the 'it's never flooded in living memory'. Flood risk is usually defined using probabilistic estimates of flood rarity which are well beyond living memory. For example flood zone 3 is a 1% exceedance likelihood, or, to put it another way, an event that is likely to occur on average, once in every 100 years. There are a couple of things you could consider. The flood maps vary in quality depending on where you are, as the underlying models also vary depending on whether there has been a need to recently update them. This is difficult to determine from the online mapping, but it might be that you're not really in flood zone 3! Only a review of the models would tell. Secondly, as others have mentioned, there are potentially creative ways around it. If you are only just within the flood zone, it may be that levels and velocities are low, so you can get away with a minimal amount of engineering. Unless you have detailed knowledge, it may prove tricky getting permission, but worth seeing how far you can get and understanding as much as you can before engaging anyone else. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2019 Share Posted October 16, 2019 Anecdote about flood risk: When we were gathering information for our planning application, during 2012, part of it came from the village history group (historical use of our plot). They were very helpful, and I asked when the area had last flooded. The answer came back that it had never flooded in living memory. We were also in zone 3, so a 1:100 year risk. We got our PP in 2013 and started the build proper in October. We went away for Christmas 2013, and whilst travelling down to Devon we got caught in some pretty bad flooding, and only just made it to our hotel in time. When we got home in the New Year we found that many houses in the village had flooded, including the lower area at the entrance to our plot (had we been living there we'd not have been able to get in or out for a couple of days). Since the house has been finished we've had two more, smaller, flooding events, both of which restricted access in or out of the house for a time. We've concluded that "living memory" has nothing to do with risk probability... Link to comment Share on other sites More sharing options...
jamieled Posted October 16, 2019 Share Posted October 16, 2019 There's been a concerted effort to try and move away from return period expressions of event probability as it tends to cause the EA some problems. However, exceedance probability type statements aren't often easily understood either so there's no easy answer and the return period is still commonly expressed. FWIW, I think fz3 is 1% or greater chance of flooding, and therefore it could be a lot more frequent than that. I suppose it might also depend on the nature of the risk - culvert and bridges backing up and causing flooding often have more to do with debris accumulation than the probability of the storm event itself. To the OP - the above is a bit academic, but my main point would be not to take any assessment of risk at face value! FZ 3 is split into 2 categories by the local authorities, 3a and 3b and this is not (I think) shown on EA maps, but does determine acceptability. 1 Link to comment Share on other sites More sharing options...
ProDave Posted October 16, 2019 Share Posted October 16, 2019 When I lived in Oxfordshire, we lived in a low lying village on the River Thame. I didn't give much thought to it when we bought it and at no point in the buying (or indeed when we sold it) was there any mention ever made of flood risk. It was soon apparent (first winter) that one of the two roads into the village flooded regularly. Okay that was an inconvenience and sometimes meant a longer journey to go the other way. It also became apparent that sometimes, not as often, the other road flooded. It was always passable but I remember having to drive through flood water every day for weeks one winter. At least 2 cottages in the village flooded regularly, and had been adapted so it was just a matter of put the furniture up on blocks, and mop it all out when the river went down. Several others regularly could not get their cars to their houses and had to don a pair of waders to get home. As it happened our house was on about the highest part of the village, but even then, the flood water one year was almost to our drive, but the house was a metre higher up a bank so still not really at risk. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2019 Share Posted October 16, 2019 One (expensive!) option to maintain a low roof line yet be able to tolerate flooding, might be to do as that riverside Grand Designs build did a few years ago, and make the whole house able to float upwards if the area floods. Bit extreme, but I wonder how cheaply such an arrangement could be designed? It must be possible to design a floating raft "foundation", held in place by piles that extend above ground level, for less than the giant floating concrete structure they used on the GD build. Maybe just using off-the-shelf floating dock stuff? Probably too wild an idea... 1 Link to comment Share on other sites More sharing options...
PeterW Posted October 16, 2019 Share Posted October 16, 2019 3 minutes ago, JSHarris said: Probably too wild an idea... we designed a round house a while back for a riverbank setting that had a 8ft diameter caisson in the bank and then a centre pin the house stood on. From that there were 4 angled arms, each with a section of screw thread connected to a central drive that in the event of flooding would pull the arms inward and allow the house to lift up by up to 4 feet ... Now that was barking mad ..!! 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 16, 2019 Share Posted October 16, 2019 3 minutes ago, JSHarris said: Probably too wild an idea... Think that is called a barge. Bit like when Kevin McClod put his caravan in a whole, but more watertight. There was a bit in the climate press the other day about flood risk. The 1:100 events are now 1:20 while the 1:1000 are coming in at 1:100. That is globally I think, but the UK is not well places geographically. But having said that, after a month of daily rain, I have not seen any bad floods. A few years back we had some bad ones. What I have seen is a lot more ditch cleaning by farmers. So maybe lack of maintenance caused some of the problems down here. Who knows. 1 Link to comment Share on other sites More sharing options...
Ed Davies Posted October 16, 2019 Share Posted October 16, 2019 There have been quite a few houses built like that in the Netherlands. Not that big a deal other than the need for the service connections to be flexible. Obviously, there are a lot of houseboats there plus fairly ordinary-style houses which float but also some which are normally ordinary land-based houses but are designed to float when flooding happens. 1 Link to comment Share on other sites More sharing options...
Mr Punter Posted October 17, 2019 Share Posted October 17, 2019 I have done several houses in flood risk areas near a river. A flood risk assessment was carried out which looked at historic flooding - depth, velocity, speed of inundation, likely return period. They consulted the Environment Agency and were informed of minimum habitable floor levels. The ground floors are flood resilient - concrete floor with tiles, rendered concrete block internal g/f walls, brick and block external. Non-habitable rooms only on g/f (office / study / store / garage). Upper floors for kitchen, living and bedrooms. In the event of a flood you would probably need new skirtings, pipe boxings, a couple of internal doors and redecoration, so not a catastrophe. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 17, 2019 Share Posted October 17, 2019 52 minutes ago, Sensus said: Looking at the map you've now attached to your original post, you're only just in FZ2? Have you commissioned a Flood Risk Assessment, yet? It shouldn't cost anything like the £4K quoted by JSHarris (I regularly commission them... we do a lot of work in South Lincs, where most of the county is in FZ3 - cost is typically around £650-£750 for that sort of site). You will need one for the Planning Application, and getting a professional to do it is far more sensible than trying to cobble something together yourself, in all but the most straightforward situations. The flood risk consultant, if selected carefully, will also have excellent contacts and credibility with both the EA and the LPA, and will be able to manage liaison on your behalf. You most certainly don't need to be looking at anything as ridiculous as an amphibious house. I can assure you that my neighbour did pay around £4k for his flood risk assessment. He complained bitterly to me that he felt it had been done by a bunch of students as a part of their course work (no idea if that's true or not). Link to comment Share on other sites More sharing options...
Mr Punter Posted October 17, 2019 Share Posted October 17, 2019 29 minutes ago, JSHarris said: I can assure you that my neighbour did pay around £4k for his flood risk assessment. He complained bitterly to me that he felt it had been done by a bunch of students as a part of their course work (no idea if that's true or not). I have paid £4,900, £1,080 and £540. The expensive one was in 2007 but it did help us gain consent and the rules were not so clear cut then. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 17, 2019 Share Posted October 17, 2019 1 minute ago, Sensus said: Maybe he did. I can assure you that it shouldn't have cost anything like that much, though. An FRA should only cost that much if they have to do full flood modelling (and even then, that's on the steep side). Just found a (very tatty) copy of the part of the FRA that was included in his D&A, as an annex. Somewhere I have the whole FRA, with all the sections through the brook, likely levels, flow rates, etc, but I have a feeling that it must be archived, probably on an old PC, as it dates back to when we were submitting our planning application back in 2012. This is the tatty file that I've been able to find on the planning website: 12792.pdf Link to comment Share on other sites More sharing options...
KimB Posted October 17, 2019 Author Share Posted October 17, 2019 41 minutes ago, JSHarris said: I can assure you that my neighbour did pay around £4k for his flood risk assessment. He complained bitterly to me that he felt it had been done by a bunch of students as a part of their course work (no idea if that's true or not). We are just in flood Zone 3, only have the land!!!! We haven't as yet commissioned a Flood risk assessmentyet. The architect we are using is only returning from holiday today, and has said we are on his priority list. Can we only use EA or can we use an independent company to do the flood assessment do you know? Link to comment Share on other sites More sharing options...
KimB Posted October 17, 2019 Author Share Posted October 17, 2019 9 minutes ago, JSHarris said: Just found a (very tatty) copy of the part of the FRA that was included in his D&A, as an annex. Somewhere I have the whole FRA, with all the sections through the brook, likely levels, flow rates, etc, but I have a feeling that it must be archived, probably on an old PC, as it dates back to when we were submitting our planning application back in 2012. This is the tatty file that I've been able to find on the planning website: 12792.pdf Thanks, I can open this!! I'll take a look. Link to comment Share on other sites More sharing options...
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