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?
P
pagoni202022 Jun 2020 20:07I strongly doubt that this will give you anything more than a false sense of security. If anything, it’s better to consistently save the money and consciously accept the risk.
Exactly – live with the inherently unpredictable risk, save money, and in the worst case, accept the consequences of your own decision. That would be my approach. No one can predict the future, and as with other things, you have to assess the risk yourself and live with it. Full protection doesn’t exist, or it becomes extremely expensive and apparently unattractive.
Exactly – live with the inherently unpredictable risk, save money, and in the worst case, accept the consequences of your own decision. That would be my approach. No one can predict the future, and as with other things, you have to assess the risk yourself and live with it. Full protection doesn’t exist, or it becomes extremely expensive and apparently unattractive.
P
pagoni202022 Jun 2020 20:10Baumaxxx schrieb:
I believe that building in already developed areas will become increasingly important in the future, and I think this is the right approach socially, instead of continuously developing new residential areas on greenfield sites. However, this completely misses my point. If someone is a millionaire and can choose any plot they want, with an unlimited budget, they probably wouldn’t be here in the forum.And why not....?????Regarding the risk again:
I do not live near the lower Elbe or Danube rivers, but rather in the upper course and near an old river branch. There has been a canal for 100 years that leads over a reservoir to the power plant. There are also agricultural floodplain areas. To allow the power plant to continue operating during floods and to prevent fields from being flooded, the floodwater is diverted into the old river branch. The dam here has been reinforced several times and is regularly maintained, including tree removal...
Of course, in theory, such a dam could break, which would lead to an extreme flood event (HQEXTREM). If nothing is done and I open my front door, water would eventually stand about 60cm (24 inches) high in my living room. This will not happen immediately; I am not located in the lowest part of the residential area, and most likely, the water would be redirected back into the canal and/or into the agricultural floodplains. This would probably not be welcomed by the power plant operators and the farmers. There is also civil protection and fire brigade that would likely try to repair the dam. In any case, in such an event, it is possible that the 60cm (24 inches) level would not be reached or even that nothing would happen at all. Such flooding has not occurred in the last 70 years since this residential area was established. None of the surrounding 100+ houses have any flood protection, and almost all have basements.
I am building without a basement, using solid construction with bricks, concrete, and polystyrene insulation, with tile flooring—so not a wooden or cardboard box. The house has already been slightly elevated to reduce the risk of heavy rainfall flooding. Of course, anything can happen...
I find it difficult to estimate damages, but they are probably around €10,000 (±), as the water would not enter the house as fast as in disaster movies. I have comprehensive natural hazard insurance that covers flood damage (100€/year).
Meanwhile, besides information from the building authority, I have gathered other insights. There are basically three options. The legal regulations are vague; you should protect yourself, but it is not specified what exactly must be done—this was also confirmed by the building authority:
1. Raise the house by 80cm (31 inches): The safest option! This would completely change the house concept as I imagine it. I want to build as barrier-free as possible to easily access the garden and the house. This option is therefore not feasible for me. After consultations, I also underestimated the costs of this concept and the significant construction delays, which together could amount to €30,000 or more. This option is recognized by the insurance.
2. Mobile flood barriers around the house with ground sealing: Very safe, but also around €20,000 to €30,000. Recognized by insurance.
3. Mobile flood protection at the house itself: Depending on the system, this can ideally prevent the worst, especially if the floodwater does not remain for long, providing good protection. There are several systems available; my preferred one has been certified by TÜV for up to 60cm (24 inches) floodwater. Recognized by insurance. Costs are €3,000 to €4,000—I am still waiting for a precise quote. → Most likely, I will choose this system. Additional measures include raising the heat pump and breaker panel slightly higher, fortunately, the electricity supply comes from the roof.
After a phone conversation with the building authority, nothing speaks against the mobile system.
It is quite remarkable what kind of amounts come up when asking about EXPERIENCES with flood protection systems... You cannot protect yourself against everything, no matter how much money you have, and when building a house, you have to set priorities and live with risks...
If anyone has PERSONAL experience with mobile dam-barrier systems, I would be very grateful.
I do not live near the lower Elbe or Danube rivers, but rather in the upper course and near an old river branch. There has been a canal for 100 years that leads over a reservoir to the power plant. There are also agricultural floodplain areas. To allow the power plant to continue operating during floods and to prevent fields from being flooded, the floodwater is diverted into the old river branch. The dam here has been reinforced several times and is regularly maintained, including tree removal...
Of course, in theory, such a dam could break, which would lead to an extreme flood event (HQEXTREM). If nothing is done and I open my front door, water would eventually stand about 60cm (24 inches) high in my living room. This will not happen immediately; I am not located in the lowest part of the residential area, and most likely, the water would be redirected back into the canal and/or into the agricultural floodplains. This would probably not be welcomed by the power plant operators and the farmers. There is also civil protection and fire brigade that would likely try to repair the dam. In any case, in such an event, it is possible that the 60cm (24 inches) level would not be reached or even that nothing would happen at all. Such flooding has not occurred in the last 70 years since this residential area was established. None of the surrounding 100+ houses have any flood protection, and almost all have basements.
I am building without a basement, using solid construction with bricks, concrete, and polystyrene insulation, with tile flooring—so not a wooden or cardboard box. The house has already been slightly elevated to reduce the risk of heavy rainfall flooding. Of course, anything can happen...
I find it difficult to estimate damages, but they are probably around €10,000 (±), as the water would not enter the house as fast as in disaster movies. I have comprehensive natural hazard insurance that covers flood damage (100€/year).
Meanwhile, besides information from the building authority, I have gathered other insights. There are basically three options. The legal regulations are vague; you should protect yourself, but it is not specified what exactly must be done—this was also confirmed by the building authority:
1. Raise the house by 80cm (31 inches): The safest option! This would completely change the house concept as I imagine it. I want to build as barrier-free as possible to easily access the garden and the house. This option is therefore not feasible for me. After consultations, I also underestimated the costs of this concept and the significant construction delays, which together could amount to €30,000 or more. This option is recognized by the insurance.
2. Mobile flood barriers around the house with ground sealing: Very safe, but also around €20,000 to €30,000. Recognized by insurance.
3. Mobile flood protection at the house itself: Depending on the system, this can ideally prevent the worst, especially if the floodwater does not remain for long, providing good protection. There are several systems available; my preferred one has been certified by TÜV for up to 60cm (24 inches) floodwater. Recognized by insurance. Costs are €3,000 to €4,000—I am still waiting for a precise quote. → Most likely, I will choose this system. Additional measures include raising the heat pump and breaker panel slightly higher, fortunately, the electricity supply comes from the roof.
After a phone conversation with the building authority, nothing speaks against the mobile system.
It is quite remarkable what kind of amounts come up when asking about EXPERIENCES with flood protection systems... You cannot protect yourself against everything, no matter how much money you have, and when building a house, you have to set priorities and live with risks...
If anyone has PERSONAL experience with mobile dam-barrier systems, I would be very grateful.
T
T_im_Norden23 Jun 2020 18:43It's great that you were able to resolve this in cooperation with the building authority.
W
Wolfgang196322 Oct 2021 15:59Hello
Our plot is situated below the HQ100 flood level line after the flood in the Ahr valley, and I am also looking for a solution to avoid raising the planned house. I am searching for the most cost-effective mobile flood protection option. Since we are planning very wide floor-to-ceiling windows, barrier boards are not an option.
What solution have you found for 3-4k?
Our plot is situated below the HQ100 flood level line after the flood in the Ahr valley, and I am also looking for a solution to avoid raising the planned house. I am searching for the most cost-effective mobile flood protection option. Since we are planning very wide floor-to-ceiling windows, barrier boards are not an option.
What solution have you found for 3-4k?
Wolfgang1963 schrieb:
Our plot is located below the HQ100 line after the flood in the Ahr Valley, and I am also looking for a solution not to raise the planned house height. What is the point of this folly in planning not to respond to the adjustment of the HQ100 line?
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