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?
H
hampshire23 Oct 2021 19:39Wolfgang1963 schrieb:
Our property is located below the HQ100 flood line after the flood in the Ahr Valley. I’m sorry to hear that.
QUOTE="Wolfgang1963, post: 535092, member: 57673"]
I am also looking for a solution that does not involve raising the planned house’s elevation and am searching for the most cost-effective mobile flood protection system. Since we plan to install very wide floor-to-ceiling windows, dam beams are not an option.
[/QUOTE]
That sounds like ignoring the reality of the situation. Hopefully, it works out well.
Build your house higher.
Anything else is saving money in the wrong place.
Explanation
Our municipality participated in a program to model flood scenarios. This started in 2018, well before the Ahr Valley events. Some houses in the town center are calculated to be at risk, although they have never had flooding issues before.
Our old house had a very high flood risk, while the new house is built 120 cm (47 inches) higher and is now only rated as moderate risk. Neither the old nor the new house was below the 1-in-100-year flood level (HQ 100 line). This concerns extreme events. For comparison, 1-in-100-year events involved rainfall intensities calculated at 53 milliliters per hour (ml/hr), with extreme events reaching up to 128 milliliters per hour (ml/hr).
In your case, a 1-in-100-year event meant water in the basement, and in an extreme event, the bed on the upper floor could be floating.
Anything else is saving money in the wrong place.
Explanation
Our municipality participated in a program to model flood scenarios. This started in 2018, well before the Ahr Valley events. Some houses in the town center are calculated to be at risk, although they have never had flooding issues before.
Our old house had a very high flood risk, while the new house is built 120 cm (47 inches) higher and is now only rated as moderate risk. Neither the old nor the new house was below the 1-in-100-year flood level (HQ 100 line). This concerns extreme events. For comparison, 1-in-100-year events involved rainfall intensities calculated at 53 milliliters per hour (ml/hr), with extreme events reaching up to 128 milliliters per hour (ml/hr).
In your case, a 1-in-100-year event meant water in the basement, and in an extreme event, the bed on the upper floor could be floating.
