# Nonlinear Bedload Transport Trajectory Angle Expressed in a Traditional Form: Derivation and Application

David M. Waterman, Marcelo Horacio Garcia

Research output: Contribution to journalArticle

### Abstract

The most common bedload transport calculation methods use an equation for the vector direction that is a linear function of the transverse slope. Existing theoretical formulations that account for nonlinear effects when transverse slopes are steep (such as noncohesive stream banks) are not widely used in practice, due largely to the complexity of their implementation. In this analysis, a single equation for the bedload transport rate direction is derived that accounts for the nonlinearity. The equation is cast in the same form as most linear formulations, but with the constant replaced by a function that requires the equation to be solved numerically. Negligible streamwise slopes are assumed, which allows the simplified expression; otherwise, the derivation follows past rigorous theoretical treatments that are valid for transverse slopes up to the angle of repose. A direct comparison is made between linear and nonlinear derivations that highlights the approximations inherent in the linear form. Application of the equation to two different types of past experiments illustrates the degree of error associated with evaluating bedload data involving steep transverse slopes using a traditional linear form for the vector direction.

Original language English (US) 04019028 Journal of Hydraulic Engineering 145 8 https://doi.org/10.1061/(ASCE)HY.1943-7900.0001619 Published - Aug 1 2019

trajectory
Trajectories
Experiments
nonlinearity
experiment

### ASJC Scopus subject areas

• Civil and Structural Engineering
• Water Science and Technology
• Mechanical Engineering

### Cite this

In: Journal of Hydraulic Engineering, Vol. 145, No. 8, 04019028, 01.08.2019.

Research output: Contribution to journalArticle

title = "Nonlinear Bedload Transport Trajectory Angle Expressed in a Traditional Form: Derivation and Application",
abstract = "The most common bedload transport calculation methods use an equation for the vector direction that is a linear function of the transverse slope. Existing theoretical formulations that account for nonlinear effects when transverse slopes are steep (such as noncohesive stream banks) are not widely used in practice, due largely to the complexity of their implementation. In this analysis, a single equation for the bedload transport rate direction is derived that accounts for the nonlinearity. The equation is cast in the same form as most linear formulations, but with the constant replaced by a function that requires the equation to be solved numerically. Negligible streamwise slopes are assumed, which allows the simplified expression; otherwise, the derivation follows past rigorous theoretical treatments that are valid for transverse slopes up to the angle of repose. A direct comparison is made between linear and nonlinear derivations that highlights the approximations inherent in the linear form. Application of the equation to two different types of past experiments illustrates the degree of error associated with evaluating bedload data involving steep transverse slopes using a traditional linear form for the vector direction.",
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AU - Garcia, Marcelo Horacio

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N2 - The most common bedload transport calculation methods use an equation for the vector direction that is a linear function of the transverse slope. Existing theoretical formulations that account for nonlinear effects when transverse slopes are steep (such as noncohesive stream banks) are not widely used in practice, due largely to the complexity of their implementation. In this analysis, a single equation for the bedload transport rate direction is derived that accounts for the nonlinearity. The equation is cast in the same form as most linear formulations, but with the constant replaced by a function that requires the equation to be solved numerically. Negligible streamwise slopes are assumed, which allows the simplified expression; otherwise, the derivation follows past rigorous theoretical treatments that are valid for transverse slopes up to the angle of repose. A direct comparison is made between linear and nonlinear derivations that highlights the approximations inherent in the linear form. Application of the equation to two different types of past experiments illustrates the degree of error associated with evaluating bedload data involving steep transverse slopes using a traditional linear form for the vector direction.

AB - The most common bedload transport calculation methods use an equation for the vector direction that is a linear function of the transverse slope. Existing theoretical formulations that account for nonlinear effects when transverse slopes are steep (such as noncohesive stream banks) are not widely used in practice, due largely to the complexity of their implementation. In this analysis, a single equation for the bedload transport rate direction is derived that accounts for the nonlinearity. The equation is cast in the same form as most linear formulations, but with the constant replaced by a function that requires the equation to be solved numerically. Negligible streamwise slopes are assumed, which allows the simplified expression; otherwise, the derivation follows past rigorous theoretical treatments that are valid for transverse slopes up to the angle of repose. A direct comparison is made between linear and nonlinear derivations that highlights the approximations inherent in the linear form. Application of the equation to two different types of past experiments illustrates the degree of error associated with evaluating bedload data involving steep transverse slopes using a traditional linear form for the vector direction.

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