It would be good to have an option in underground stormwater controls to have a separate option for exceedance level and Ground Level
By taking the exceedance level as GL, it makes the Long sections look distorted when in reality it is common for our designs to have circa. 1m+ cover from top of tanks/soakaways etc to ground level.
Thank you for the suggestion and thanks to those who voted. InfoDrainage does allow you to define your depth/area diagram in a way to represent the top of the tank and then use the exceedance level to define the ground level. It would take one timestep for the water to flood from the top of the tank when you make the area very small between the top fo the tank and the ground level.