Embankment of land in a "flood" area

Thank you very much for your messages.

There are currently no concrete alternatives – but we are basically still looking. We liked the plot because it is quite rural and the proximity to the Danube has its appeal.

I will look into the insurance issue in more detail soon. At short notice, I checked with online providers – a flood or natural hazard insurance would basically be possible, with an additional cost of about €300 per year. Whether that is sufficient, I cannot say at the moment.

Regarding the soil survey: According to the municipality, there is apparently a report that can be viewed in the office. I will take a look on site at some point and copy an excerpt for [tiefblauer]/the architects.

For your information.

"An HQextrem (extreme flood) is a flood event with a discharge (Q) that (statistically) occurs very rarely and can lead to significantly higher water levels than an HQ100. An HQextrem roughly corresponds to an HQ1000. The HQ value is determined or estimated according to uniform standards based on the data available for the water body. In the case of an HQextrem, flood protection structures are generally no longer effective, as they are not designed for such a scenario. This scenario can therefore also provide indications of which areas could be flooded in the event of a dike breach."

Has there ever been an event HQextrem in the last 1000 years?

Yes. You can be lucky... but if you're unlucky, the house is ruined and you don't know if an insurance company will accept it. The online calculators don't provide precise information. If you check the box for elemental damage, the insurance will first examine it in detail and you will receive an individual offer... or a rejection. Based on the pictures from the Ahr Valley, I would rather not buy such a plot of land.

Whether such an event has ever occurred is not really relevant. Statistically, it happens every 1,000 years, but that does not mean it can't happen 3 times in 10 years. These statistics are not really meaningful anyway, because climate change makes extreme events much more likely than was the case 100 years ago. The assumption "last year there was a once-in-a-century flood, so now I have 100 years of peace" is dangerously wrong.

You need to fill around 1,000 m³, so something like 1,500-1,800 tons, depending on what you bring in. That alone is already 75-90 truckloads with a 4-axle truck. Then it still has to be installed with an excavator. The price for the material is rather secondary here; the costs mainly depend on where they can get the fill material from, so how long the routes are for the truck or trucks...

And for the foundation of the house, it probably won't be the simple strip foundation, but something with well rings, piles, or similar. You should at least expect that, so you are not caught off guard when just the foundation slab alone calls for 100,000 EUR.

You have to fill about 1,000m³

Why? In my opinion, only the area for the house, (terrace?) and the driveway need to be raised.

Why? In my opinion, it's only about raising the area for the house, (terrace?) and the driveway.

And the rest remains 1.5m below street level? You don't even have to wait for a flood; it already fills up like a swimming pool during every heavy rain...