A tutorial on the piecewise regression approach applied to bedload transport data

A Tutorial on the Piecewise Regression Approach Applied to Bedload Transport DataSandra E. RyanLaurie S. PorthUnited StatesDepartmentof AgricultureForest Service General Technical Report RMRS-GTR-189Rocky Mountain Research Station May 2007Ryan, Sandra E.; Porth, Laurie S. 2007. A tutorial on the piecewise regression ap-proach applied to bedload transport data. Gen. Tech. Rep. RMRS-GTR-189. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 41 p.AbstractThis tutorial demonstrates the application of piecewise regression to bedload data to define a shift in phase of transport so that the reader may perform similar analyses on available data. The use of piecewise regression analysis implicitly recognizes dif-ferent functions fit to bedload data over varying ranges of flow. The transition from primarily low rates of sand transport (Phase I) to higher rates of sand and coarse gravel transport (Phase II) is termed “breakpoint” and is defined as the flow where the fitted functions intersect. The form of the model used here fits linear segments to different ranges of data, though other types of functions may be used. Identifying the transition in phases is one approach used for defining flow regimes that are essen-tial for self-maintenance of alluvial gravel bed channels. First, the statistical theory behind piecewise regression analysis and its procedural approaches are presented. The reader is then guided ...