Bill Cross pulled his truck to the side of a dusty mountain road and jumped out to scan a stretch of rapids rippling through the hillsides below. As an expert and a guide, Cross had spent more than 40 years boating the Klamath River, etching its turns, drops and eddies into his memory. But this run was brand new. On a warm day in mid-May, he would be one of the very first to raft it with high spring flows. Last year, the final of four…