Actually, you do have that.
Key difference is that it is only going to apply to the perimeter where water is going to make its way in. If there is a building on top of the garage, don't forget to account for rain hitting the sides of the building and coming down the sides.
What is happening to the rain on the roof?
One major source of water I can think of is at the entry/exit(s). Rain on any ramps or swells is going to flow in toward the garage.
I don't know the details of the garage's design, so it is up to up to evaluate all potential means for water to enter the garage and design the drainage system accordingly. I would expect a lot of drains around the perimeter with few if any in the middle.
Are you in a flood zone? Does the jurisdiction you are building in have any special flood zone requirements?