ARkStorm@Tahoe: Addressing social and ecological resilience to extreme winter storm events in the Sierra Nevada

Background/Question/Methods

Atmospheric rivers (ARs) are strongly linked to extreme winter precipitation events in the western U.S., accounting for ˜80% of extreme floods in the Sierra Nevada and surrounding lowlands. In 2010, the U.S. Geological Survey developed the ARkStorm extreme storm scenario for California to quantify risks from extreme winter storms and to allow stakeholders to better explore and mitigate potential impacts. The scenario was constructed by combining two historical AR storm episodes and quantified by simulating them using the Weather Research and Forecasting model nested within global climate model data fields, resulting in a historically plausible 23-day storm sequence. To explore impacts to natural resources and communities in montane and adjacent environments, the scenario was downscaled to 2-km resolution over a 150 km² area that included the greater Lake Tahoe, Reno, and Carson City region of California and Nevada. This ArkStorm@Tahoe scenario was presented at six stakeholder meetings, each with a different geographic and subject matter focus, and discussions were facilitated to identify social and ecological vulnerabilities to extreme winter storms, science and information needs, and proactive measures that might minimize impacts from this type of event. Information collected in these meetings was used to develop a tabletop emergency response exercise and set of recommendations for increasing resilience to extreme winter storm events.

Results/Conclusions

Over 300 individuals participated in ARkStorm@Tahoe stakeholder meetings and the emergency response exercise, including representatives from the emergency response, natural resource and ecosystem management, health and human services, public utilities, and business sectors. Interruption of transportation, communications, and lack of power and backup fuel supplies were identified as the most likely and primary points of failure across multiple sectors and geographies, as these interruptions have cascading effects on natural and human environments by impeding emergency response efforts. Natural resource impacts of greatest concern include flooding, impacts to water quality, spread and establishment of invasive species, and interactions with other disturbance types (e.g., fire, landslides). Science needs include improved monitoring and models to facilitate better prediction and response, real-time and forecast inundation mapping to understand flood risks, vulnerability assessments related to geomorphic hazards and water quality impacts, and development of alternative scenarios to understand an even broader range of potential impacts. Results from this effort highlight several opportunities for increasing the resilience of communities and the environment to extreme storm events.