The pilot of the single-engine airplane reported that during landing to the southeast, a gust of wind contacted the airplane's tail from the left side, causing the airplane to veer to the left. The airplane departed the runway, crossed a taxiway, and impacted a ditch. The pilot reported there were no preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the airplane. Examination of the wreckage by a Federal Aviation Administration inspector revealed the nose gear collapsed and the propeller was bent aft. The engine firewall was wrinkled below the left engine mount. The recorded weather at the airport, about the time of the accident, included wind from 080° at 10 knots.