Project overview: Develop a critical, comprehensive flooding and drainage study for Yosemite Valley, which hosts a substantial amount of the park’s offices, housing, visitor services, and historic properties.

How your support helps: Yosemite Valley has never had a comprehensive drainage and flood study. This has greatly hindered the park’s efforts to improve drainage infrastructure in the Valley, leading to widespread damage and the flooding of transportation corridors and sewer systems during recent atmospheric river events and 2023 spring runoff. Climate change is expected to increase the intensity and frequency of atmospheric river storms, which have historically caused the largest floods in Yosemite Valley. 

The park currently uses temporary fixes, such as closures, sandbags, and sump pumps; it has permanently lost multiple facilities to flood damage. Yosemite National Park has a critical need for a comprehensive flooding and drainage study for Yosemite Valley to gather information on flooding and drainage in order to protect valuable assets and provide for visitor and employee safety. 

This year: The Valley Flooding and Drainage Study, which will be completed by 2026, will provide necessary information for park leadership to protect and manage existing facilities, transportation corridors, and historic properties, as well as develop infrastructure projects that are resilient to future hydrologic conditions. 

Project partners: Yosemite National Park

Matt Outhier

Project Notes

"Climate change is expected to increase the intensity and frequency of atmospheric river storms, which have historically caused the largest floods in Yosemite Valley. This proposal funds necessary studies to provide the park with information on flooding and drainage in order to protect valuable assets and provide for visitor and employee safety."