Outback 2012 leaking passenger side floor

I bought my outback 1/12, it is nearly one year old with 18000 miles. I have been frustrated with three instances of severe leaking to passenger side of car which soaks the carpet each time. It happens every time I am driving and it is raining. My service rep and tech says it is a clogged evap core drain from tree debris. I called Subaru of America customer service, their answer was to offer free cleaning once a year while under warranty. My concern as I explained to them is this is a severe leak into a new car which seems to be a design flaw and could lead to mold or even rust problems in the future. Besides the free declogging( $13 was the charge) during warranty ( not usually covered under warranty as is an outside force!) Subaru does not have a fix for this problem. After reading online about leaks in Subarus it does not seem to be a new problem for this model car. Why have they not fixed this flaw? I have owned many cars over the last 40 years and have never had a water leak in any car new or old. The other suggestion was to avoid parking under trees to avoid debris! Really! I thought cars were meant to be outside. Any suggestions from this forum would be appreciated. Thank you