On October 16, 1999, at 1245 eastern daylight time, a Cessna 182S, N783WW, was substantially damaged when it collided with trees during the landing roll at Airhaven Airport (09N), Staatsburg, New York. The certificated private pilot was not injured. Visual meteorological conditions prevailed for the personal flight that originated at Danbury, Connecticut (DXY), approximately 1200. No flight plan was filed for the flight conducted under 14 CFR Part 91. In a telephone interview, the pilot stated he departed Danbury, Connecticut, approximately 1200, for the flight to Airhaven. He said that he got his weather information from the Automated Terminal Information Service (ATIS) at DXY, and the winds were from 230 degrees at 11 knots. The pilot performed his approach to land on runway 20 at 09N and touched down "...just above the stall speed." The pilot said he used back pressure on the control yoke during the rollout to keep the nose wheel off the runway. According to the pilot, he applied the brakes, lowered the nose, "...and lo and behold, there was a deer! I applied left brake to avoid the deer and went down an embankment I was unaware of." The airplane departed the left side of the runway, struck brush, and sustained damage to the left wing, the left main landing gear, and the propeller. When questioned if there were any mechanical deficiencies with the airplane, the pilot responded, "None whatsoever." The pilot reported approximately 600 hours of flight experience. He said he began flying in 1959 and accrued approximately 300 hours of experience before he stopped flying in 1961. The pilot said he resumed flying in February 1998. He reported 300 hours of flight experience since that time, 200 hours of which were in the Cessna 182. The sod runway at Airhaven Airport was 1,750 feet long and 75 feet wide. The winds reported at Poughkeepsie, New York, 12 miles south of Airhaven were from 250 degrees at 10 knots.