The pilot reported that during the initial climb, he leveled off at about 65 feet above the ground and made a right turn to follow a river. After maneuvering down the river for about one minute, the airplane struck uncharted and unmarked power lines that spanned across the entire length of the river. He reported that the impact from the power lines cracked the windscreen and damaged the vertical stabilizer, but aircraft control was not affected and he was able to continue to the destination airport about 3 nautical miles away. The pilot further reported that he never saw the power lines that the airplane impacted, but he did observe larger charted power lines about one mile ahead. The left vertical stabilizer was substantially damaged. The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation.