What lies to either side of your garage?
What type of garage door do you have?
Depending on how much water is getting, instead of a trench you could build a hump?
but I need to see it, first.
Can you post some pics.
BTW I am a licensed contractor, junior accountant, bar tender, chef, cis teck, my own lawyer, real estate agent, forklift driver, DJ, etc. Trying to get my pilot license.