Abstract
Low-tech approaches for restoring riparian areas aim to initiate or engage or remove certain hydrologic, geomorphic, and biologic processes that are currently lacking or not appropriate for the potential of the site. By doing so, these approaches aim to speed up or jump-start the natural restoration cycle of the stream and quickly move the site into a fully functioning condition. This restoration approach has been spreading over the western U.S. as a way to deal with nearly two centuries of stream and riparian degradation that has left thousands if not millions of kilometers of streams in a condition that does not meet the potential of the site. This project set out to understand the state of the science around process-based approaches; provide quantitative answers to how low-tech restoration approaches effect the hydrology, geomorphology, and vegetation of the stream; and share a framework for how to undertake monitoring and adaptive management. We conducted a methodical synthesis and meta-analysis of existing literature; planned, implemented, and monitored a four-year restoration project on a rangelands stream; and developed an adaptive management and monitoring framework suitable for future work. From the synthesis, we found that relatively few restoration projects were reporting results, but those that did generally showed improvements in hydrologic, geomorphic, and vegetation processes consistent with the hypothesis that intervention can restore these processes to a functioning condition. Though there were several studies that reported results not consistent with the overall direction of the process-based approach, which may be due to site-specific conditions or poor planning and design. Our restoration project found that the low-tech approaches slightly effected surface and sub-surface water quantity and timing; geomorphic change from erosion and deposition could be evaluated using drone-based images; and vegetation composition shifted towards species with more affinity for wetter sites. The monitoring and adaptive management framework shows how process-based monitoring can help identify actions and the sequence of steps necessary to achieve restoration objectives. We show how this approach can be applied on public and private lands throughout the West, with Idaho as the specific example.