On May 8, 2001, about 1650 hours Pacific daylight time, a Beech BE77, N3865D, landed in rough terrain and brush near Riverside, California, while practicing maneuvers over and around Lake Mathews. The airplane was substantially damaged and the student pilot received minor injuries. The training flight was operated by Riverside Air Service under 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated at 1600 from Riverside. According to the student pilot, he was finishing up a few power on and power off stalls, when he thought he would practice a couple of emergency landings. He was familar with the procedure and had practiced them several times with no problems. The first attempt was sucessful. However, on the second attempt, he began his climb-out with flaps fully extended and full power. He was subjected to turbulence from the right, raising the right wing, at which time he lost some altitude. He regained control with aileron and rudder input. He realized that he was not climbing, instead he was losing altitude. He said that he never regained enough altitude to raise the flaps. He was faced with a forced landing in rough terrain and thick brush.