Pulled the below from "US AIR FORCE HISTORICAL RESEARCH AGENCY" is a very good read, check it out , as for the the ditch / landing see below:
Air Force (USAF) counted World War II aerial victory credits only for USAAF flyers, or Allied aviators who belonged to USAAF units. The action had to occur between December 7, 1941 and September 2, 1945. Only fighter pilots or members of night fighter crews were eligible. The enemy aircraft had to be airborne, heavier than air, manned, and armed. Destruction involved shooting an enemy aircraft down, causing the pilot to bail out, intentionally ramming the airplane to make it crash, or maneuvering it into the ground or water. If the enemy airplane landed, despite its degree of damage, it was not counted as destroyed.
I would propose that a ditch by its definition would mean to put the aircraft into water, therefore different from a landing, although HTC definition of a ditch would also include solid ground, which I could not find any definition to support, but my research was inadequate and short.
HL