Rapid hydrological responses following process-based restoration in a
degraded Sierra Nevada meadow
Abstract
Mountain meadows are ecologically important, but often degraded,
groundwater dependent ecosystems that retain and store water in upland
forested landscapes. They tend to occur in low-gradient, broad valleys
where water naturally slows and sediment accumulates, making them
efficient locations for restoration. Over a century and a half of land
use has degraded many meadows in the Sierra Nevada, reducing their
hydrological and ecological functionality. Process-based restoration is
a potentially economical and scalable restoration approach for numerous,
small, remote, degraded mountain meadows. The approach uses onsite
materials and leverages fluvial processes to achieve restoration
objectives including increases in wetted area, groundwater elevations,
sediment capture, and development of multithreaded channels. These
changes in hydrological functionality can lead to improved ecological
function over time. This study compares pre- and post-restoration
surface and groundwater conditions in a degraded riparian meadow in the
Sierra Nevada, California U.S.A. to understand changes in meadow
hydrogeomorphic function following process-based restoration.
Restoration included the installation of 35 postless beaver dam analog
structures in ~1 km of incised meadow channel.
Stage-discharge data at the inlet and outlet of the project area were
paired with groundwater data collected from 15 wells distributed across
the meadow in a power law model to estimate increased water storage of
3700 m 3 (~3 acre-ft) due to
restoration. After the wet winter of 2023, we estimated that pools
behind structures filled to over half their volume with fine sediment.
We also applied hydrodynamic modeling to evaluate fluvial changes at
high flows and found that restoration increased flow complexity and
wetted surface area. These short-term responses highlight the potential
speed and effectiveness of low-tech, process-based restoration in
achieving desired restoration outcomes.