Tabular Representation of Cross-Sectional Elements

A convenient and consistent method for representing the top width, area, first moment of area, and second moment of area for an irregular stream cross section is presented. The variation of top width is taken to be piecewise linear and continuous. The top width is then integrated exactly to obtain the values for the other elements. The unique features of the method is the use of integration to not only define the tabulated values, but also for interpolating for values not tabulated. This procedure yields values consistent with the mathematical definition of the elements. The errors introduced by the operational assumptions and the errors inherent in the basic top width data are separately estimated in an example. A comparison of these two errors is used to evaluate the adequacy of the assumption made for top width.