Air Vents Pouring Water!

I put a hose into the cowl vent so I could clean out the drain holes. Lots of garbage came out from both sides! All of my older cars had this issue, so not unexpected. What was unexpected was that after I spent about 30 minutes cleaning out the drains, I saw the floorboards on both sides were full of water. None of the cars I had in the past with fresh air vents had that much of an issue with water pouring in from the vents.

I expected the first time I opened the fresh air doors that garbage would blow out at highwat speeds... and it did! Is there a secret I don't know about to ensuring the drain holes are really clear so this does not happen again during a rainstorm?