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Hawaii Trail Surveys and Risk Management Summaries

How the state of Hawaii uses a social profile and trail user survey of Diamond Head Trail, Oahu. an environmental and recreation risk management plan for trails on the Hawaiian Islands.

From Hawaii Trail Analysis Survey & Risk Management Data Profile: download complete document (95 pages, illustrations, tables; pdf format 4.0 mb)
Also see "The Design and Placement of Warning Signs on Improved Public Lands"

By University of Hawaii at Manoa, Practicum 751, March, 2001

Map of HawaiiThe State managed trails system in Hawaii is one of the most geographically diverse systems in the United States. Hawaii has a high concentration of trails in relatively close proximity to one another. Along with the privileges of access to public land come responsibilities on the part of both the managing entity and the public.

On the part of the state, this means maintaining trails for safe travel while preserving the natural ecosystems or cultural resources. In places where the safety of trail users may be reduced, it is the responsibility of the state to inform trail users of the risks they may potentially encounter. Trail users are responsible for their own awareness and level of preparedness. They are entrusted to enjoy the most intimate places in the islands with as little negative impact as possible.

Photo: rocky trail crossing stream

Trail users navigating slippery rocks on the Manoa Falls Trail

This portion of the report introduces the results of the user survey and also of the physical assessment. The survey determined how prepared and aware users actually were, and the physical assessment noted what hazards they should be conscious of. This section first gives overview information that is significant to the entire state. This information is then broken down by island and then more specifically by trail.

TRAIL AND PARK USER CENSUS

There are potential trends that can be seen among the trails on Oahu:

  • People are most likely to hike in pairs
  • Between 20% -25% of the groups were composed of single hikers
  • The majority of users heard about the trail by word of mouth
  • More than 50% of the users on each trail wore running shoes
  • More than half the users (Diamond Head excluded) notified someone not with them that they intended to go hiking
  • 13% - 17% of the users of each trail had previously gotten lost while hiking
  • Less than 12% of the users admitted to leaving the marked path
  • Over 90% of the users recalled the existence of signage on the trail, yet what they recalled seeing varied widely

Diamond Head Trail Use Survey

photo of Diamond Head mountain
Diamond Head, site of a popular Oahu hiking trail

An extremely high-use trail, the Diamond Head trail on Oahu is a steep 1.4-mile hike inside Diamond Head Crater which leads visitors to the Leahi Summit. The trail is dry and the craterÕs interior can be extremely hot due to a lack of wind.

The trail begins as a paved pathway and continues as an improved dirt path with a gradual incline and over 250 stairs until reaching the 760 foot summit. For those that reach the top, the summit affords a 360-degree panoramic view of southern Oahu.

There is currently a charge of $1 to enter the State Park. Between 1500 and 2500 people visit the park daily and it is estimated that 1.3 million people visit the landmark every year.

Hazards:

  • Heat, sun exposure
  • Erosion and falling rocks
  • Unstable footing
  • Risk of Fire
  • Strenuous climb
  • Darkness in tunnels and bunkers

Diamond Head User Profile

Photo of concrete trail
The Diamond Head Trail begins with a paved walkway

Diamond Head is visited primarily by tourists (85% non-local hikers). Some locals hike the trail for exercise and meditation in the mornings. A large number of hikers are Japanese tourists. These groups often could not be surveyed because of a language barrier and /or a refusal to participate in the survey.

Therefore, the data for this trail does not necessarily paint a representative picture of trail users. (Example: at least 5 people were observed wearing heels on the trail but none could be surveyed.) The users that were surveyed, on average, were older than those surveyed on other trails (39% over 45 years old).

Social Profile of Trail and Trail Users Survey

The survey team set up about a quarter mile into the trail, where the pavement ends and the improved dirt path begins. This location was chosen as the majority of people passing this point intended to hike to the summit. During each survey period (with the exception of the early morning survey period), less than half of those passing by were surveyed. This was due to the sheer numbers of people hiking. The variance in the total number surveyed is attributed to the numbers of surveyors. There were between two and four interviewers at each survey period, and the second survey period included 2 Japanese speaking interviewers. The majority of people were hiking "because it was Diamond Head," one of the "must-do" activities when visiting Oahu. The highest use occurs between 10:00AM and 2:00PM, when more than 250 people enter the trail each hour.

Physical Profile of Diamond Head Trail

photo of trail in tunnel
The tunnel and concrete bunker network along Leahi Ridge on the way to the summit of Diamond Head Crater

Most of the hazards on this trail are associated with the intensity of its use. The beginning of this trail deceivingly gives the impression that this is a well-developed trail, as there is a wide paved sidewalk for the first quarter of a mile. After this point, the trail surface is eroded basalt originally routed by the US Army when they occupied the crater. The army also constructed the tunnel and concrete bunker network along Leahi Ridge, which provides the route for the last half of the trail.

The destination is an eroded bunker at the peak of Leahi which affords dramatic views of Waikiki, Honolulu, Koko Head, and the leeward side of the Koolau Mountain range. The mean annual rainfall is less than 20 inches. The vegetation in the crater consists of kiawe ( Prosopis pallida) and haole koa ( Leucaena leucocephala), with an understory of fingergrass. Thus, there is no protective canopy. There are no streams along the trail. There are five potential hazards that exist on the Diamond Head Crater Trail: trip and fall, exposure/fatigue, brush fire, landslide/rockfall, and infrastructure-related issues.

Trail Surface:

The trail surface beyond the paved sidewalk is extremely eroded and uneven, creating a potential traction hazard. This is intensified by the fact that users may experience fatigue due to exposure to the sun. The route is lined with handrails in its entirety to assist the mass of people to reach the summit. The uneven path may cause tripping. This hazard increases if the user leaves the path and attempts to climb the steep crater walls. The trail surface at the tunnels and beyond are predominantly paved. Aging military bunkers await the user at the destination.

Climate & Topography:

Photo of steep steps and railings
The sign reads "Staya behind railing for your safety and to prevent erosion"

Because of the lack of shade and the steep grade for most of the climb, fatigue is a serious concern. Hikers often expect an easy climb with a few exciting dark tunnels and then reach a great view. This is evident in the choice of dress, selection of footwear (such as loafers and sandals), and provisions.

The average age of the Diamond Head user is higher than at other trails, which makes these choices even more critical to the safety of the trek. There is no water available to users beyond the trail head. Due to the low annual rainfall, dry vegetation, and non-hiker smokers, there is a considerable fire hazard threat.

Landslide/Rockfall:

The loose, crumbly soils in the crater combined with the steepness of the crater walls provides ideal conditions for erosion, either in the form of incremental rockfall or mass movements of substrate. The fractured rock that composes the crater slopes may gradually lose stability and fall. The fact that there are several switchbacks on a given slope allow for a falling rock to hit a number of potential targets. The high volume of the trail increases the likelihood of contact with a trail user. Users that ignore posted signs and leave the trail are subjected to increased risk of not only slip and fall, but also inadvertently creating a rockfall that may impact users on the trail below.

The trail route ventures through two sections of tunnels and one spiral staircase, both without the benefit of lighting. The tunnels and stairs were not designed for mass-movements of people, but for military operations, and have not been modified significantly since army occupation. The pill boxes through which the trail runs are in poor repair and are difficult to negotiate for some users. Pill boxes not on the trail course may tempt more adventurous users to leave the trail and experience greater risk exposure.

Existing Management Practices:

There are a considerable number of signs throughout the trail reminding people to not leave the trail, to not smoke, etc. The handrails are helpful to keeping people on their feet. As for the fire hazard, there are access roads to manage a potential blaze, but those users who happen to be caught at the top will have to wait out the fire or wait to be rescued. Improvements to the trail and bunker area are scheduled for January, 2000, and should address many of the infrastructure related issues mentioned above.

Possible Action Steps:

There is little that can be done about the fire hazard except to continue to prohibit smoking in the park and have a fire evacuation plan. Exposure and fatigue could be reduced through construction of simple shelters with benches at various points on the trail, and by providing water. Landslides will continue to be a potential threat regardless of removal or reinforcement of hazardous slope areas, and this risk could be communicated through a consolidated signage program at the trailhead and/or at points where the hazard is present.

From Hawaii Trail Analysis Survey & Risk Management Data Profile: download complete document (95 pages, illustrations, tables; pdf format 4.0 mb)

Also see "The Design and Placement of Warning Signs on Improved Public Lands"

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