Reference Manual (RM #47) Chapter 4: Planning

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5 minutes, 40 seconds

An introduction to how to incorporate acoustic resources into park planning

4. Planning Process

Acoustic monitoring at Chapin Mesa, Mesa Verde National Park, NPS Photo.

NPS uses planning as a way to apply best available science and methods to natural resource and visitor management in order to make better decisions that will benefit park resources. Through the planning process, parks become more aware of the issues and opportunities surrounding sounds and acoustic resources and their relationship to other resources and values. Parks also are better poised to make good decisions, develop meaningful partnerships and create effective policies. The acoustic environment can be affected by a multitude of NPS decisions and practices. Planning efforts related to park programs and activities such as transportation, maintenance, facilities, wilderness, natural resources, cultural resources, and law enforcement should consider acoustic resources and noise management.

Great Gallery Detail, Horseshoe Canyon, Canyonlands National Park. NPS Photo Neal Herbert

The acoustic environment is a resource with intrinsic value. It is important as a natural resource, a cultural resource, or both. It is a critical component of wilderness character, and plays an important role in wildlife communication, behavior, and other ecological processes. Results from surveys, across multiple decades, of the American public indicate that hearing the sounds of nature is an important part of the visitor experience in national parks (Haas and Wakefield 1998, Ferguson et al. 2024). Therefore, the value of acoustic environments and soundscapes is related to an array of park resources and has broad implications for park management. Since the quality of the acoustic environment is relevant in nearly every unit in the NPS System, park staff should consider the acoustic environment as a resource with inherent value in park plans and strategies.

A variety of laws, regulations, and policies direct the NPS to address acoustic resources and soundscapes in their planning process. The primary guidance for national park managers are the 2006 Management Policies and Director's Order #47. Management policy 4.9 requires parks to use appropriate planning to identify what levels of noise can be accepted within the established management purposes of parks. The pitch (frequency), loudness (decibel level), duration, and source of noise considered acceptable will vary throughout a park, and will differ between parks. Developed areas generally have more occurrences of noise, more variety in sound sources, and louder sound levels. Undeveloped areas generally have fewer noise occurrences and fewer sources of noise. Undeveloped and backcountry areas can be influenced by noise generated in more developed areas; low frequency or deep, rumbling sounds of motors are most commonly heard because these frequencies travel farther in the environment. Further, culturally significant areas will have cultural soundscapes that include human and natural sounds.

Cottonwood Cove on Lake Mohave, Lake Mead NRA. NPS Photo Andrew Cattoir.

Director's Order #47 builds on the principles in Management Policies, but goes on to direct how and when to consider acoustic resources in park management. Through this order, parks are guided to manage noise by identifying noise sources, minimizing noise from park operations, considering the acoustic environment in park planning documents, and promoting park sounds and noise management through communication, education and outreach.

Central to the NPS wide planning framework is the park planning portfolio—the assemblage of planning documents that guide park management and decision making and satisfy law and policy. Director’s Order #2 clarifies that the totality of documents in a park’s planning portfolio fulfills a park’s planning needs, including meeting the requirements for a general management plan (GMP), and provides guidance on a variety of planning documents that guide park decision making, including foundation documents, comprehensive plans, strategic plans, and implementation plans. Director’s Order #47 compliments Director’s Order #2, emphasizing how acoustic resources and the acoustic environment should be considered in a variety of planning types and situations, including standalone acoustic resource management plans where and when necessary.

In addition to these service-wide directives, there are park-specific references about the importance of protecting intrinsic soundscapes and related values and resources embodied in parks' enabling legislation. For example, in parks' establishing legislation and supporting information you can find terms such as "ecological integrity," "extensive, unaltered natural ecosystems" [PDF], "remote wildness and solitude," "serenity," "a contemplative visitor experience," or "promoting solemn appreciation," in relation to a park's purpose and significance. Throughout the planning process it is important to have a clear understanding of your park's enabling legislation and any other relevant laws, regulations, policies, or existing planning documents that set the framework for acoustic resource management. Establishing a strong justification for noise reduction and soundscape protection makes subsequent management actions easier to implement and facilitates coordination among other stakeholders to address threats to park resources.

4.1 Establishing Acoustic Zones

• Acoustic zones are areas that should be managed in a similar fashion (same objectives, thresholds, and indicators)
• Acoustic zones may correspond to one or more park management zone

Fall colors in Oak Creek, Zion National Park. NPS Photo Cadence C. Cook

4.2 Acoustic Resource Objectives

Resource objectives offer the park an opportunity to specify the intention of how to manage the resource based on goals defined in the various planning products. In setting acoustic resource and soundscape objectives, consider these key questions:

• What is the existing condition?
• What is the desired condition and what acoustic conditions are being protected?
• What are the interrelationships of the various resources influenced by acoustic resources and/or noise?
• What park activities are fundamental to visitor experience and to park purposes?
• Where, when, and for how long are certain activities appropriate?
• How can parks minimize impacts of administrative and visitor activities on the acoustic environment?

Simply put, "objectives" answer the questions "what do we want the park to sound like?"or "what do we want visitors and wildlife to experience in our park?" The answers to these questions inform park management plans. Since each park, its acoustic environment, and noise sources are unique to each plan and setting, the management objectives will vary from park to park and among management zones. Objectives and standards must be established based on the unique acoustic conditions and management goals of each park.

Zoning is a common planning and management technique in older General Management Plans (GMPs) or Master Plans as well as newer smaller planning documents. Generally, zones in parks are used to categorize areas of a park broadly into areas of similar use such as motorized transportation corridors, developments areas, and natural areas. Natural areas are often further subdivided to recognize designations such as wilderness or recommended wilderness. As a matter of course, these different areas of the park will likely have different acoustic environments. While in some cases those broad designations may be adequate for acoustic management planning, some parks may wish to consider more detailed zoning for setting desired soundscape conditions. This may be especially true at parks where the acoustic environment is a fundamental resource and the park is trying to protect areas with highly intact natural acoustic environments but must also manage intense areas of infrastructure or transportation noise (including aircraft).

For example, Zion National Park's GMP [PDF] identifies seven management zones, each with different soundscape objectives. The zones include: frontcountry high development zone, frontcountry low development zone, transition zone, Primitive zone, Pristine zone, Research natural area zone, and Administrative zone. Acoustic resource management is also addressed in the natural resources, visitor use and experience, issues and concerns, and future planning sections of the GMP. The soundscape objectives are further described in the 2010 Soundscape Management Plan (SMP) that tiered from the GMP (see below). Since the soundscape objectives for Zion are well developed and resonate in both GMP and SMP, we include them in this reference manual in order to demonstrate the breadth of objectives that a park could establish.

Instameet June 2016, Zion National Park. NPS Photo

Soundscape Objectives for the Frontcountry Zone

• Natural sounds are audible and discernable, with common noise intrusions by visitors and park operations that are concentrated at locations near roads and heavily developed areas. ·
• Active intensive management is used to maximize noise free intervals and limit the intensity and duration of noise intrusions.
• Noise levels that interfere with general conversation rarely occur and are of limited duration except when caused by emergency services, search and rescue operations (sirens, search and rescue aircraft), and park operations (road repairs, grounds and building maintenance).
• Noise levels that interfere with interpretive programs do not occur except when caused by emergency services and search and rescue operations (sirens, search and rescue aircraft).
• Noise levels that exceed thresholds for sleep interruption rarely occur.
• Noise levels at common rock climbing areas should not interfere with effective communication among climbers. Noise levels that mask important auditory signals for wildlife should be uncommon and should be limited to locations near roads and heavily developed areas.
• Noise levels that affect wildlife behavior, distribution and numbers should be uncommon and should be limited to locations near roads and heavily developed areas.

The Perseid Meteor Shower, Zion National Park. NPS Photo

Soundscape Objectives for the Wilderness Zone

• Only natural sounds are audible and discernable, except for short duration, infrequent noise events.
• Sound levels that interfere with general conversation are very rare and are of limited duration except when caused by emergency services, search and rescue operations (aircraft), and approved park operations (aircraft, motorized/mechanical tool use).
• Sound levels that exceed thresholds for sleep interruption are extremely rare.
• Sound levels at rock climbing areas and technical canyons should not interfere with effective communication among climbers and canyoneers.
• Sound levels that mask important auditory signals for wildlife should be rare. Sound levels that affect wildlife behavior, distribution, and numbers should be rare.

A view from high above the rest, Denali National Park. NPS Photo

4.3 Indicators and thresholds

Many park units have a variety of zones ranging from front country and developed areas to remote backcountry and wilderness. Sounds that are appropriate in some areas of the park are inappropriate in other zones. Outlining in park plans appropriate and inappropriate noise sources is an essential component of resource protection. When developing plans, such as transportation or visitor use management plans that include specific resource goals associated with the acoustic environment, it is important to set objectives that are measurable and rooted in the acoustic conditions and management goals.

So that park managers are able to track progress towards achieving the goals and objectives, condition indicators and measurement thresholds should be established for the resource. Indicators are measurable, manageable proxies for desired park conditions which are responsive to thresholds, defined as numerical expressions of desired conditions for indicators. For example, the National Park Service might use durations of noise-free intervals as a good indicator related to providing visitors opportunities to experience natural sounds and quiet. A good threshold for this indicator might specify that at least 90% of visitors will experience at least one interval of 15 minutes or more that is free of human-caused noise while visiting the park.

Another example is to establish quantitative indicators, target values, and long term, comprehensive management strategies to achieve and maintain desired natural and cultural resource conditions over time. An "indicator" could be the occurrence of non-natural sounds as expressed by percentage time audible per day. The "target value" would be non-natural sounds are audible less than 10% of the day in no more than 25% of the area.

When Denali National Park completed its backcountry management plan (BCMP), three acoustic indicators with thresholds for each of the various management zones created by the plan were established:

1. Percentage of any hour when motorized noise is audible.
2. Number of motorized noise intrusions per day that exceed natural ambient sound.
3. Maximum motorized noise level. For more information, see Table 2-5 from the BCMP.

The Denali BCMP delineates an extensive monitoring program to track progress towards achieving objectives. Other good examples include Zion National Park's Soundscape Management Plan, which employs many useful metrics. In Kenai Fjords National Park's Exit Glacier Area Plan, the thresholds are exceptionally low due to quiet conditions in the park.

Once thresholds have been identified, it is necessary to conduct monitoring to determine whether or not goals are being met. In the event that conditions do not meet threshold goals, noise mitigation efforts should be identified and implemented. Subsequent monitoring should identify the effectiveness of the mitigation. For more information on adaptive management, see this technical guide [PDF] or the Interagency Visitor Use Management Council guidebooks. Using an indicators and thresholds approach for monitoring and managing resource conditions is a common and accepted practice, but may not be necessary for every scenario.

4.4 Develop Mitigation Strategies to Achieve Objectives and Standards

Once goals, objectives, indicators, and thresholds are established for management zones in your park, it is time to determine mitigation strategies that will protect, preserve and restore the acoustic resources of the park. Just as acoustic conditions are unique to each place, mitigation activities will be unique to your park. Further, each park has other resource management goals and human resource or financial parameters that will shape what mitigation is appropriate and logical for the park. See Chapter 6: Common Noise Sources and Mitigation.

4.B Planning Documents
For examples of specific planning documents that address protection of the acoustic environment see 4.B Addressing the Acoustic Environment in Common Planning Documents.

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Appendix A: Glossary
Appendix B: Authorities