Carport drainage, calculate water quantity

Hello, can someone tell me how to calculate the drainage of a carport? We want to build a carport and still have to inform the authorities about our drainage. The carport will not be connected to the sewer! We want the water to basically seep into a hole behind the carport, but don’t know what all needs to be considered for that! Does anyone happen to have an idea? Thanks already

Simply specify a trench infiltration. This may be sufficient for the building authority since you are not discharging anything from the carport. Otherwise, you must calculate and prove the appropriate trench size.

The question is, how do you calculate [ist das].

Flat roof? Google "calculate rainwater input online." Then you have the amount of water that the infiltration trench must absorb. At Graf, for example, you can request a calculation for their products. In my opinion, that should be sufficient. Or does the building authority have specific requirements?

So Google throws out a thousand things to me, but nothing really understandable. There must be a simple calculation for that, right?

Yes, it is a flat roof. 6x9m.
What is Graf?

It doesn't get any easier: "Calculate rainwater donation online - Roofer Müller"

Graf manufactures cisterns and soakaways. If you have the total amount of water that needs to infiltrate, Graf will size the soakaway for you. Of course for their products, but you can use it as a reference and should have a calculation that meets the building authority's requirements.