Hello Johannes,
This is how a understand the curb inlet parameters:
[i]In the manual is written that the invert level describes the point at which the spilling starts, does that mean that this is the invert level of the pipe for the water transport from the inlet to the pipe network? [/i]
It is actually the invert level of your curb inlet, considering the way you define your nodes this is Ground Level – High of the Inlet (10cm i.e.). It works actually as weir crest.
[i]Is the freeboard defined as a water level on the street?[/i]
The freeboard is a parameter to ensure computation stability (avoid fluctuations). While running MIKE URBAN flood simulation two water levels are computed one in the MOUSE engine (MU) and the external MIKE FLOOD engine, then to estimate the discharge from one model into the other it is necessary to verify where the water level does is located either in the MU or in the MF surface. This is used to identify the direction of the flow 1D into 2D ( orifice equation) or 2D into 1D model (QQ relation or DQ relation).
The freeboard defines a critical water level (Invert level- Freeboard) at the connection node in the pipe network below which the defined DQ relation apply. For submerged and reverse flow (surcharge), the transfer capacity of the connection reverts to a standard orifice relationship.
Have fun modelling