UNIVERSITY PARK, Pa., Sept. 1 -- Pennsylvania State University issued the following news release:

UNIVERSITY PARK, Pa. - Over the past two days, 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 will face as extreme weather events become more common, according to Bing Pan, professor of recreation, park, and tourism management at Penn State.

Beyond visitor safety, national parks have a potentially contradictory dual mission: protecting natural areas while also facilitating recreational use of those areas....