Short term effectiveness of high density large woody debris in Asotin Creek as a cheap and cheerful restoration action.

摘要

In response to human impacts, river restoration and rehabilitation actions have become a priority in the United States. In the Pacific Northwest, most restoration actions are focused on repairing degraded freshwater habitat to increase or improve Pacific salmonid production. However, traditional river restoration actions remained largely unchanged for over 100 years despite a lack of definitive evidence that the actions were effective. Recently, we have been developing "cheap and cheerful" restoration actions that are low impact, cost effective, can be implemented over large scales, and target degraded processes. However, because cheap and cheerful restoration is a relatively new method, and restoration effectiveness monitoring is universally lacking, the success of these types of projects has not been assessed.;To address this issue, I studied the short-term physical effectiveness of a type of cheap and cheerful restoration that uses high density large woody debris (HDLWD) to restore instream habitat complexity in two wadeable tributaries to Asotin Creek in southeast Washington State. Additionally, I developed a mobile database application to facilitate data collection using a novel rapid restoration effectiveness assessment survey.;Results indicate that the structures are effective at imposing several immediate hydraulic responses following installation. These hydraulic responses increase hydraulic roughness, which results in predictable geomorphic responses following high flow events. Following restoration, the number and area of pools and bars significantly increased within treatment sites, while the number and area of planar units decreased. Likewise, it appears that the addition of the structures has encouraged a 25% increase in depositional volume at treatment sites compared to control sites.;Results from the rapid assessment approach supported the more vetted approaches used to assess the efficacy of the treatment. However, my results indicate that inter-observer variability when using the rapid protocol may be high, and visual estimates of geomorphic unit area are inflated. Analysis of the rapid assessment approach revealed pertinent improvements to the application and rapid protocol that will be made before the approach can be broadly applied.