Terrain modeling different from the building application - allowed? (NRW)

You stay more than 3 meters away from the boundary. In my humble amateur opinion: yes, go ahead. No one will come to measure the height. However, the 3-meter boundary distance should be maintained.

As already said, take a look at the building envelope and the permitted height of procedurally exempt realizable walls. 1.5m is quite a corner and in my layman's opinion not permanently achievable solely through planting rings.

In der vorliegenden Baugenehmigung

Do you have a building permit according to §68 Building Code NRW? If yes, what reasons spoke against §67? IMHO the modification requires approval because it is not an independent embankment but is connected with the construction of the house and the planned terrain modeling is part of the approval. At least the embankment is relevant for setback areas, so the approved site plan cannot be correct either, as setback areas are missing there or shown too small. Does your embankment even comply with the lateral setback areas? If you planned according to §67, your authorized building submitter should answer your question, as he signed for compliance with the regulations.

A happy new year to you and thank you for your feedback!

As already said, look at the building envelope and the permitted height of walls that can be realized without a formal procedure. 1.5m is quite a bit and, in my layman's opinion, not permanently feasible with planting rings alone.

I have no concerns about that. 6 to 7 rows of planter stones (staggered accordingly) and the slope is secured. I know slopes that are secured with this method over 2 meters high and have lasted for 35 years. However, this only refers to practical feasibility here. Not to whether it is even allowed.

Do you have a building permit according to §68 Building Code NRW? If yes, what reasons spoke against §67? IMHO the change requires approval because it is not an independent embankment but is connected with the construction of the house and the planned terrain modeling is part of the approval. At least the embankment is relevant for clearance distances, so that the approved site plan cannot be correct either, as clearance distances are missing or depicted as too small there. Does your embankment even comply with the lateral clearance distances?
If you planned according to §67, your licensed architect/engineer should answer your question, as they signed for compliance with the regulations.

I have to admit: if I were that deep into the matter, I wouldn’t have needed to ask this question here.
It is clear that our building application (drawing without red area) is an application for a "project for which the simplified approval procedure is conducted (§68 paragraph 1 sentence 2 and §67 paragraph 1 sentence 3 Building Code NRW)" and was approved as such. Which clearance distances, in what form, occur (must occur)... I have no idea about that. Hence my question here.
As for the distances to the neighboring property, these would not be changed. Everything remains in front of the 3-meter limit to the actual property boundary.

According to the development plan, only the following is recorded:
"Enclosures of front gardens in the form of living hedges are permitted up to a height of 1.0m. Enclosures of front gardens by walls or fences must not exceed a height of 0.7m."

The area in question is not between house and street, so it is not a front garden.

Project for which the simplified approval procedure is carried out (§68 para. 1 sentence 2 and §67 para. 1 sentence 3 Building Code NRW)

Okay. This suggests that you (probably because your architect wanted it) submitted an application for a building permit, although exemption from approval would also have been possible. Thus, you received a building permit after the authority checked the compliance of your construction project with the public-law regulations based on your construction documents. However, if you now carry out a different terrain modeling, the construction documents will no longer correspond to reality. Therefore, the legal certainty of the building permit is no longer given.
I recommend consulting with the architect. If he knows the people at the approval authority and has no concerns about expanding the embankment without an amendment, then I would rely on his word. If he is unfamiliar with the area or you have doubts about his competence, I advise you to inquire with your caseworker at the building authority. As I said, I consider the expansion to require approval, but maybe the staff member at your approval authority sees it differently. The legal text, in my opinion, allows for both opinions.

Thank you for the explanation !

I have tried to familiarize myself a bit with the issue of independent versus non-independent embankments. Did I understand correctly that non-independent embankments under 1 meter above the original terrain do not require approval (of course also considering the 3m distance)? If yes, then the slope could be supported by another step, which ultimately is only up to one meter high.