Recently, heavy rains have caused flooding in Grand Canyon and Zion National Parks, resulting in the loss of at least two lives. In U.S. national parks, maintaining visitor safety can be complicated because it is difficult to measure who is in a park and where they are, much less what hazards they w ill face as extreme weather events become more common, according to Bing Pan, professor of recreation, park and tourism management at Penn State. ...read more read less