Ice Age Floods National Geologic Trail Designation Act - Designates the Ice Age Floods National Geologic Trail, a trail from Missoula, Montana to the Pacific Ocean, to provide for the public appreciation, understanding, and enjoyment of the nationally significant natural and cultural features of the Ice Age Floods and to promote efforts to interpret and educate along the pathways of the floods.
Requires the Secretary of the Interior, acting through the Director of the National Park Service, to administer the Trail. Prohibits the Trail, except as provided in this Act, from being considered a unit of the National Park System (NPS). Allows the Secretary to establish and operate a Trail management office within the vicinity of the Trail.
Requires the Secretary to prepare a cooperative management and interpretation plan for the Trail.