I am currently in the building permit / planning permission process and just found out through a call to the building authority that my property is located in the HQ100 EXTREME risk zone, so I have to take flood protection measures. This requirement has apparently been in effect since 2018 in Baden-Württemberg.
To explain: HQ100 EXTREME means there is a levee protecting my site next to the Danube River, but this levee could break (which seems very unlikely...). Because of this, I need to implement additional flood protection, whatever that may specifically involve. The exact wording states:
“At locations in risk areas outside designated flood zones, where no local land-use plan exists, construction projects may only be built or significantly extended using building methods adapted to the specific flood risk, according to generally accepted technical standards, provided this type of construction is technically feasible given the nature and function of the structure.”
I am building a solid structure without a basement, and my finished floor level is 61cm (24 inches) below this theoretical extreme flood level. I do not want to raise the ground level further. Although this would be technically possible, it would be expensive and would not look good.
I spoke by phone with the responsible official about whether I could build a wall around my property as a possible solution. She said she wasn’t sure if walls that high would be permitted there and reminded me to consider the entrance driveway. She recommended building 81cm (32 inches) higher for safety, but 61cm (24 inches) might be acceptable. However, I got the impression she wasn’t very knowledgeable. Maybe installing barriers or flood gates on the doors could work – I have seen sliding flood barriers online. Overall, this is really frustrating as none of the more than 100 houses nearby (all built before 2018) have anything like this, there has never been an extreme flood, and I think potential damage would probably be less than the cost of these measures. I also have insurance that costs an additional 100€ per year for flood coverage. To be safe, I will probably install my heat pump about 0.5m (20 inches) higher.
Does anyone have experience with this or a good idea on how to solve this as cost-effectively as possible?
To explain: HQ100 EXTREME means there is a levee protecting my site next to the Danube River, but this levee could break (which seems very unlikely...). Because of this, I need to implement additional flood protection, whatever that may specifically involve. The exact wording states:
“At locations in risk areas outside designated flood zones, where no local land-use plan exists, construction projects may only be built or significantly extended using building methods adapted to the specific flood risk, according to generally accepted technical standards, provided this type of construction is technically feasible given the nature and function of the structure.”
I am building a solid structure without a basement, and my finished floor level is 61cm (24 inches) below this theoretical extreme flood level. I do not want to raise the ground level further. Although this would be technically possible, it would be expensive and would not look good.
I spoke by phone with the responsible official about whether I could build a wall around my property as a possible solution. She said she wasn’t sure if walls that high would be permitted there and reminded me to consider the entrance driveway. She recommended building 81cm (32 inches) higher for safety, but 61cm (24 inches) might be acceptable. However, I got the impression she wasn’t very knowledgeable. Maybe installing barriers or flood gates on the doors could work – I have seen sliding flood barriers online. Overall, this is really frustrating as none of the more than 100 houses nearby (all built before 2018) have anything like this, there has never been an extreme flood, and I think potential damage would probably be less than the cost of these measures. I also have insurance that costs an additional 100€ per year for flood coverage. To be safe, I will probably install my heat pump about 0.5m (20 inches) higher.
Does anyone have experience with this or a good idea on how to solve this as cost-effectively as possible?
I agree with everyone that raising the building level naturally provides 100% protection. For me, it’s not just about the additional cost of €10,000 (about $11,000); anyone who has built knows how quickly that amount can disappear.
The house would no longer fit the terrain and would not blend in with the surrounding buildings. Because of that, I might even lose the building permit / planning permission. I am building according to §34, which requires the building to integrate into the surrounding development. A huge retaining wall around the property would probably not be allowed either. Such major changes would also significantly delay construction, as the neighbors would probably need to be consulted again. Surface water must not flow onto neighboring properties, and with such a large amount of filled soil, the neighbors would be even more affected by flooding. I have already slightly raised the ground level to protect against heavy rainfall events.
But as I said, I don’t like the idea of a house perched prominently on the lot with stairs leading down into the garden, regardless of costs. There has never been a flood before, but the dam has been reinforced several times. If an extreme HQ100 flood were to occur, water would stand 60cm (24 inches) high in the living room when I open the front door; otherwise, water might seep in here and there.
Are measures like dam barriers really just symbolic? In cities like Cologne or Salzburg, they have been successfully protecting old towns with them for years. However, I have never seen them applied to residential houses, although they are sold in countless variants.
The house would no longer fit the terrain and would not blend in with the surrounding buildings. Because of that, I might even lose the building permit / planning permission. I am building according to §34, which requires the building to integrate into the surrounding development. A huge retaining wall around the property would probably not be allowed either. Such major changes would also significantly delay construction, as the neighbors would probably need to be consulted again. Surface water must not flow onto neighboring properties, and with such a large amount of filled soil, the neighbors would be even more affected by flooding. I have already slightly raised the ground level to protect against heavy rainfall events.
But as I said, I don’t like the idea of a house perched prominently on the lot with stairs leading down into the garden, regardless of costs. There has never been a flood before, but the dam has been reinforced several times. If an extreme HQ100 flood were to occur, water would stand 60cm (24 inches) high in the living room when I open the front door; otherwise, water might seep in here and there.
Are measures like dam barriers really just symbolic? In cities like Cologne or Salzburg, they have been successfully protecting old towns with them for years. However, I have never seen them applied to residential houses, although they are sold in countless variants.
Baumaxxx schrieb:
The house would no longer fit the terrain and would not blend in with the surrounding buildings; perhaps I would even lose the building permit because I am building according to §34, which requires me to integrate into the surrounding development. That is really frustrating. What does the architect say? Since this is a flood risk area, which is publicly known, wouldn’t that be taken into account during the planning? You wouldn’t have to worry now if everything had been included in the design.
Baumaxxx schrieb:
I just spoke with the responsible officer about whether I can build a wall around my property. That might be an option. She said she wasn’t sure if such tall walls are allowed there and that I also need to consider the driveway. She recommended building it 81cm (32 inches) higher, or at least 61cm (24 inches) higher. But I had the feeling she wasn’t very knowledgeable. I think she knows what she’s talking about: after all, she immediately brought up the driveway, which you hadn’t considered. She doesn’t have to worry about costs or contingencies.
Baumaxxx schrieb:
Raising the house would also cost €10,000 (about $10,900), and for that amount I could pay for insurance for 100 years. Mentioning insurance at this point is probably not appropriate. It should cover unforeseeable events and accidents—it’s a collective protection. It might even be that the fine print excludes coverage if the building is knowingly constructed differently.
P
pagoni202020 Jun 2020 09:52As you read, it seems you cannot be convinced by such a measure, which to me suggests that you have already thought it over many times and have basically reached your decision.
No one can tell you what will happen; we all can only make assumptions about the future, and you would then be building a house that you might no longer like (which I would never do). Since you have given it enough thought, I would build it as you planned.
My old house was located by the Neckar River, although in the fourth row up on a slope, and the water never reached it there. In the first year, the row in front was affected, and all the construction pits or basements plus partially the ground floors were flooded. After that, some even had boats hanging on the house walls.
You have a very clear opinion, which I can understand—I would do it that way too—and if the worst case does happen, you just have to deal with it.
In our residential area, flooding was always a consideration, so people were quite relaxed about it.
Better to take the risk of having water in the basement once in a while than to have to look at and live in an "ugly" house for a lifetime. So I can understand you.
No one can tell you what will happen; we all can only make assumptions about the future, and you would then be building a house that you might no longer like (which I would never do). Since you have given it enough thought, I would build it as you planned.
My old house was located by the Neckar River, although in the fourth row up on a slope, and the water never reached it there. In the first year, the row in front was affected, and all the construction pits or basements plus partially the ground floors were flooded. After that, some even had boats hanging on the house walls.
You have a very clear opinion, which I can understand—I would do it that way too—and if the worst case does happen, you just have to deal with it.
In our residential area, flooding was always a consideration, so people were quite relaxed about it.
Better to take the risk of having water in the basement once in a while than to have to look at and live in an "ugly" house for a lifetime. So I can understand you.
Ötzi Ötztaler20 Jun 2020 10:14
Baumaxxx schrieb:
And if this HQ100 EXTREM were to occur, water would be 60cm (24 inches) high in the living room when I open the front door; otherwise, it might seep in here and there. Since you apparently don’t want to believe it, I’ll explain slowly so you can take notes: For small streams that quickly overflow during local heavy rain and where the flooding recedes within a maximum of three hours, such measures are absolutely effective. For multi-day floods saturated with heating oil and mud from the Danube, you either need heavy-duty solutions or you might as well give up and stick to minimal cosmetic measures that only satisfy the building authority.
A small tip: have a chat with the local restaurant owners in Passau who are regularly flooded by the Danube every few years. They will certainly know what they’re talking about.
Ötzi Ötztaler20 Jun 2020 10:25
The city of Regensburg has mobile flood barriers that apparently work surprisingly well. However, they are not available for free...
Similar topics