Rainwater retention basin overflows onto the property

We bought a plot of land in a new development area a few weeks ago. As part of the development work, a new stormwater retention basin was also built, which borders directly on our property. The development is now complete, and in February we had to notice that water is standing on our property, which obviously comes from the overfilled basin. In the days before, it hadn't really rained at all. What will the situation look like when it rains heavily?! By the way, the attached photos show the basin and part of our property. It begins above or to the right of the pipe. We have asked the municipality to take care of it, but they say that this is our problem. I see this differently, as before the basin was filled there was no water (problems) on our property. What can we do?

Oh dear, that doesn't look good! Is there a road in between or does your property border the retention basin directly?

Under the condition that it is approved. To build a concrete wall around your property that is 1.5 meters high and also reaches 2-3 meters deep. Then you should have peace. However, that would not be exactly inexpensive.

However, I also wonder how the municipality can say that this is your problem. The retention basin belongs to the municipality. And as a layman I see it that they are responsible for ensuring that no water from the basin reaches your property. Aside from a storm which raises the water level in the basin by a meter or more in a very short time. I am sure if that were your basin and the water was standing on municipal land, the municipality would be at your doorstep faster than you could even say water.

I would probably already consult a specialist lawyer and ask for an assessment.

Otherwise you probably only have what I mentioned at the beginning left.

Does the purchase agreement or the land register say anything about any toleration obligations / encumbrances?

I would probably already consult a specialist lawyer and ask for an assessment.

Does the purchase contract or the land register say anything about possible toleration obligations / encumbrances?

These are the reference points you should adhere to! The building authority has already given you its opinion.

No matter which way, whether via the legal route or via the above-mentioned construction measures, it will initially be expensive. I know of no legal protection except ARAG (I believe it only applies up to a dispute value of €10k) or the insurance cooperating with Sparkasse, which applies to new construction projects.

By the way, the attached photos show the basin and part of our property. It starts above or to the right of the pipe.

Which pipe? The white one or the blue one?

And what is the white pipe for? Is there going to be a channel/water ditch?

Is the rain retention basin actually completed and operational at all?

Well, with just the two photos alone, you really can't say much. Isn't there a development plan that shows better how the whole thing is planned?