Raising a lawn

Hi, my front lawn is moss ridden and requires raising by up to 12" in parts. I am wondering if I need to completely dig out the existing lawn to put in drainage before laying sand, top soil and turf?

FYI, the lawn is 60ft x 15ft and is 100 ft away from a large mere. Possible problem, is that the house is already 2ft lower than the front lawn and I'm worried by raising the lawn it might cause flooding