The pilot reported that, while landing on a wet, grass runway, the airplane suddenly veered to the right. The airplane exited the runway and impacted a water filled drainage ditch. Subsequently, the airplane come to rest inverted. The airplane sustained substantial damage to the aft fuselage, vertical stabilizer, and left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot reported that the wind was from 100° at 15 to 17 knots and gusting. An automated weather observation station located 5 miles northeast of the airport reported that, about the time of the accident, the wind was from 090° at 12 knots, gusting to 18 knots. The airplane was landing runway 02. The airplane owner's manual states, "The maximum allowable crosswind velocity is dependent upon pilot capability rather than airplane limitations. With average pilot technique, direct crosswinds of 15 MPH can be handled with safety."