The pilot reported he was attempting to take off from a remote gravel bar. During the takeoff roll, the airplane encountered a hump in the runway which pushed the airplane to the left. Shortly after passing over the hump, the airplane became airborne. The left wing then collided with trees and brush, and the pilot was unable to maintain directional control. The airplane subsequently went off the left side of the gravel bar and came to rest in a stand of trees and brush.