Methodological Considerations in the Calculation of Effective Discharge: Application for the Trinity and Brazos Rivers



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Effective discharge (Qe) is defined as the discharge responsible for carrying the most amount of sediment over two or three decades. The first objective of this thesis is to calculate Qe for the middle Trinity River in Texas. The historic discharge data from four gaging stations is used to develop flow probability density functions for the analysis. Suspended sediment rating curves are developed using measured concentration while bedload rating curves are calculated. The second objective of this study is to use collected data to explore how calculations of Qe can be made when measurements are not feasible. Results show that effective discharge for the middle Trinity River varies from 11,000 cfs to 20,000 cfs, which is significantly smaller than Q1.5 and the bankfull discharge. Further analysis shows that historic flow data is sufficient for a reasonable estimate of Qe and that measurements of river geometry, suspended sediment concentration, and bed sediment samples do not change the calculated Qe.



Effective discharge, Trinity River