USDA Forest Service

Pacific Southwest Research Station

 
Pacific Southwest
Research Station

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Albany, CA 94710-0011
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General Technical Report

Title: Climate change vulnerability and adaptation for infrastructure and recreation in the Sierra Nevada

Author: Halofsky, Jessica E.; Peterson, David L.; Buluç, Lara; Ko, Jason

Date: in press

Source: Gen. Tech. Rep. PSW-GTR-2xx. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station

Station ID: GTR-PSW-262

Description: The Sierra Nevada Infrastructure and Recreation Vulnerability Assessment and Adaptation Partnership identified climate change issues relevant for resource management on national forest units in the Sierra Nevada region of the U.S. Department of Agriculture, Forest Service (USFS) Pacific Southwest Region. This partnership assessed the vulnerability of infrastructure and outdoor recreation to climate change, and developed adaptation options that minimize negative impacts of climate change and facilitate transition to a warmer climate.

Increasing use and aging infrastructure are increasing the vulnerability of infrastructure to the effects of climate change. Altered timing, type (rain versus snow), and amount of precipitation will create challenges when storing and allocating water for irrigation, flood prevention, and energy production. The Sierra Nevada is already experiencing temperature increases as a result of human-caused climate change. Higher winter temperatures have resulted in more precipitation falling as rain rather than snow and reduced snowpack, which in turn have led to earlier timing of streamflow; peak flows are projected to occur 1–2 months earlier by the end of the 21st century.

Roads, bridges, and culverts are susceptible to increased runoff during storm events, causing failures due to washouts, plugging, overtopping, stream diversion, and scour. Long-term climatic patterns that affect infrastructure over multiple decades—altered freeze-thaw cycle, snowmelt, and stream hydrology—can also affect the sustainability of transportation and water resource infrastructure. Increased magnitude of peak streamflows in winter is expected to damage roads near perennial streams, ranging from minor erosion to complete loss of the road. Associated infrastructure such as bridges, culverts, campgrounds, and facilities near streams and floodplains will be especially vulnerable.

At vulnerable or flood-prone sites, resilience near stream crossings and in floodplains can be enhanced by designing future infrastructure to withstand more frequent and severe flood events, and by upsizing or upgrading existing infrastructure to withstand future flooding. Some roads and other infrastructure can be decommissioned or moved to mitigate risks. Improving streamflow forecasting and expanding streamflow and snowpack monitoring networks will help managers respond to extreme events and ensure water allocation downstream.

To prevent wildfire damage to infrastructure, vegetation can be managed to reduce fuel loads and increase defensible space around facilities and transportation corridors in the wildland-urban interface. Following wildfires, managers can prioritize slope stabilization projects for infrastructure near unstable slopes and river banks, increase monitoring of soil and slope conditions, and restrict public access to sites where unstable soils create safety hazards. In general, using best management practices while employing a “climate change lens” will facilitate long-term resilience of infrastructure.

Outdoor recreation is a huge enterprise in the Sierra Nevada, providing diverse experiences and health benefits to residents of California and beyond. Nearly all recreation is affected by weather conditions, affecting decisions about if, when, and where to recreate. Summer recreation will benefit from a longer period of suitable weather without snow, especially during the spring and autumn shoulder seasons. Winter recreation (skiing, snowmobiling) will be negatively affected by a warmer climate because of less and more transient snow. Ski areas and other facilities at lower elevations will be especially vulnerable. The effects of higher temperatures on hunting, fishing, water-based recreation, and gathering forest products will be variable and less certain.

Nearly all recreation activities will be negatively affected by projected increases in extreme weather and disturbance events. Wildfire creates short-term (weeks to months) impacts by reducing visitor access to roads, trails, and recreation facilities; pervasive smoke reduces air quality over large areas within and outside national forests. Severe wildfires often kill trees across tens of thousands of acres, altering the aesthetic quality of recreation sites and vistas, and in some cases affecting plants and animals that are valued by recreationists. Dead and damaged trees, as well as postfire soil erosion, create significant hazards for recreationists that may last for decades.

Increased recreation is projected for the Sierra Nevada, so adequate staffing and resources will be needed to aid delivery of recreation opportunities and to maintain visitor safety. Limits on visitation through determination of carrying and social capacity may be increasingly necessary, as will communication about alternative recreation areas, alternative activities, and warnings about potential crowding (through websites and social media). Partnerships can supplement management for diverse recreation opportunities and settings, supporting information needs and informing adaptive responses.

Specific adaptation strategies for recreation include: (1) increase resilience of recreation infrastructure to increasing disturbances, (2) adjust staffing and management during variable shoulder seasons to accommodate changes in seasonal access and recreation locations, (3) adjust visitor management policies and practices to increase management flexibility and facilitate transitions to meet user demands and expectations, (4) increase resilience of recreation sites to changing conditions and/or increased demand, and (5) increase capacity to accommodate shifting seasonal recreation patterns. Many on-the-ground management actions are available to implement these strategies.

Collaborative adaptation efforts are essential for effective responses to the effects of climate change on infrastructure and recreation. Expanding partnerships among federal, state, and local agencies will increase the capacity of the USFS and other organizations to maintain functional ecosystems, water resources, and recreation and transportation infrastructure. The Sierra Nevada Partnership achieved specific elements of national and regional climate change strategies for federal agencies, providing a scientific foundation for resource management and planning in national forests and beyond. Timely implementation of adaptation will help prevent the deterioration of infrastructure and the huge costs of repairs and replacement, and will ensure the sustainability of facilities, access, and opportunities for recreation. Long-term monitoring will help detect potential climate change effects, as well as evaluate the effectiveness of adaptation options.

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Citation

  • Halofsky, J.E.; Peterson, D.L.; Buluç, L.; Ko, J., eds. [in press]. Climate change vulnerability and adaptation for infrastructure and recreation in the Sierra Nevada. Gen. Tech. Rep. PSW-GTR-2xx. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station.