Departure Analysis: Compare to Baseline Sediment Yield

Potential consequence of increases in sediment and/or channel stability changes.

This is the KEY step in summarizing and interpreting the previous analysis results. Adverse potential channel adjustments leading to channel instability and morphological shifts have long-term adverse effects on beneficial uses. In summary, Flowchart 20 (PDF, 33 kb, 1 p.) predicts sediment supply/stability.

There are four worksheets that contribute to summarizing sediment/stability ratings:

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• Worksheet 31 (PDF, 13 kb, 1 p.) summarizes total sediment, entrainment results and stability by individual reach or sub-watershed;
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• Worksheet 32 (PDF, 81 kb, 1 p.) documents the relative contributions of sediment by process and stability summary for an individual watershed;
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• Worksheet 33 (xls) summarizes the sediment source and stability ratings for a range of sub-watersheds and stream systems; and
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• Worksheet 34 (xls) provides a comparison of multiple watersheds and river systems for their respective sediment contributions and stability effects.

These worksheets conclude the PLA. The interpretations at this point are instrumental at formulating future watershed plans and restoration or stabilization efforts. The PLA represents a strong foundation for understanding the cause and consequences of the watershed problems causing adverse river impacts. These worksheets help document specific locations and sources that may require site-specific mitigation.

The effects of both upstream and downstream water uses are considered as well as on-site potential changes. This step leads the analyst to recommend process-specific mitigation and management changes that will potentially balance sediment supply and channel stability to improve beneficial water uses. It is critical that the final steps of this assessment provide a consistent and clear linkage to the sources and erosional/depositional processes leading to change. It is only in this manner that a proactive approach can be taken for stabilization, remediation, restoration and/or enhancement once analysis is complete. "Best Management Practices" are most effective when specifically directed to the processes and sources related to adverse change.

Although often case-specific and outside the immediate scope of WARSSS, an overview of related monitoring is also presented. Monitoring in conjunction with WARSSS results is critical in order to:

1. Verify the relations used to predict sediment and stability change
2. Determine the effectiveness of process-specific mitigation measures, stabilization, restoration enhancement, etc., and
3. Document short-term as well as long term sediment stability (and beneficial uses) response.

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