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ID: 2463

Hales, G., A. Hilton, S. McBain, and S. Howlin. 2020. Statistical evaluation of Trinity River point bar bed mobility and bed scour during annual spring ROD releases for WY 2009 - 2013. Report for the Trinity River Restoration Program (TRRP). McBain Associates, Arcata, California. Available: https://www.trrp.net/library/document?id=2463.

Bed mobility and scour are fundamental TRRP objectives for physical processes. Field-based monitoring of bed mobility and scour accurately documents bar response to annual flows, allowing comparisons with physical process management objectives in the ROD (i.e., were Trinity River Flow Evaluation bed mobility and scour objectives met in any particular water year by winter flood or ROD releases?). However, field monitoring requires annual resources and does not provide a quantitative prediction of bar mobility and scour response to various flows. Recently improved 2-D hydraulic models can be used to provide deterministic predictions of bar response, but historic application of these models has shown modest performance, and results are specific to every bar due to unique hydraulic conditions.

The objective of this analysis was to determine if a statistical model, using all bed mobility and scour data collected since 2009 across multiple WY types, could be developed to predict bed mobility and scour on point bars in the restoration reach. Statistical models were developed from a population of 111 sites with bed mobility experiments and 114 sites with bed scour experiments, to determine (a) the probability of a site having >80% bed mobility, and (b) the probability of a site achieving >1.0 D84 scour, across a range of flows and specific inundation zones. Results can allow managers to use predicted values, with associated confidence, to evaluate management actions relative to the predicted probability of mobility and scour, and then integrate management decisions and anticipated outcomes across disciplines.

First Posted: 2020-02-25 17:54:49

Post Updated: 2020-02-25 18:05:23