The aircraft departed Parkes on a VFR flight to Coffs Harbour, tracking via Scone, Mount Seaview and Kempsey. The pilot reported that the weather enroute to Scone had been fine with clear skies and winds from the south at 10 kts, however, active storms were observed developing to the south of the intended track. Shortly after the aircraft passed over Mount Seaview, the pilot assessed that the weather was unsuitable to continue flight on his planned track. He decided to follow the Macleay River valley to Kempsey, then continue coastal to Coffs Harbour. However, about 5 NM before Kempsey the weather deteriorated rapidly, forcing the pilot to divert in order to remain in visual meteorological conditions. An area of high ground, which he had overflown some minutes earlier, was chosen for a landing. The pilot made two precautionary passes over the area and believed that the surface was approximately level. He then approached to land toward the south, but discovered upon landing that the surface had a considerable downslope. While attempting to stop the aircraft the wheels locked under braking and skidded on wet ground. The right main landing gear collided with a creek bank, slewing the aircraft at right angles to the landing direction, and resulting in substantial damage.