NPS Photo

Figure 1. Visitor queues form at the base of the Half Dome cables as a result of crowding. While queuing was not found to occur frequently, conditions far less crowded than shown (90 people on the cables from the top of visual range to the first stanchion) impeded free-flow conditions on the cables. This photo represents three times as many people on the cables at one time as the standard the park is seeking to maintain.

Yosemite National Park is recognized for its towering granite cliffs and surreal waterfalls. Located in the Sierra Nevada of California, the park is also renowned as a popular recreation destination that at times experiences high levels of visitation. While the experiences of most visitors are concentrated in the easily accessible areas of Yosemite Valley, high levels of visitor use are also documented on wilderness trails (Broom and Hall 2010), including the Half Dome Trail (HDT) (fig. 1, above).

The HDT hike has long been the setting of an iconic experience in Yosemite National Park. The trail leads visitors up the only route accessing the summit without technical climbing. The hike is 16 miles (26 km) round-trip ascending 4,000 ft (1,219 m), and is an undertaking that culminates with the last 400 ft (122 m) of the ascent exposed and on the Half Dome cables (fig. 1, above, and fig. 2). This structure consists of pairs of heavy-gauge cables approximately 32 inches apart secured to the rock surface at varying intervals of 82 to 296 feet (25–90 m) in length. The cables are suspended by stanchions that vary from waist to shoulder height and provide handholds, while boards anchored to the stanchions afford footing (fig. 2 inset). The cables form a corridor that facilitates travel to the summit of Half Dome. The structure is typically installed by the trail crew in mid-May and available for use through mid-October, dependent upon weather.

In recent years this hike has transformed from what was historically thought to be a multiday wilderness experience to an epic day hike for most visitors, with an increasing number of search-and-rescue incidents. Fourteen falls and four deaths have been recorded in the vicinity of the Half Dome cables since 1969, with eight incidents occurring since 2006. Most of these falls were caused by weather events resulting from wet surfaces, but three falls occurred when the cables were down while one happened under crowded conditions.

Iconic park destinations can require extensive operations to minimize the effects of crowding, manage traffic, improve safety, protect wilderness values, and provide search-and-rescue services. This article illustrates and outlines a process in support of science-based decision making to manage visitor use on the Half Dome Trail. The cables section of this trail does present an additional opportunity to frame visitor experience with safety as the biggest driver in determining daily use levels. This investigative process provides rationale for decision making that maintains high-quality visitor experiences and is designed to withstand public scrutiny. The defining elements of this process are issue identification, scientific investigation, interim management measures, park planning commitments, monitoring, and operational refinements.