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Confidence Levels for Estimating RDI/I

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Estimates or projections of RDI/I (rainfall dependent inflow and infiltration) often appear in the literature without including information about the level of confidence in the final results. This paper contains the results from using two objective statistical tests: r (coefficient of linear correlation for the amount of variation of RDII resulting from changes of rainfall), and the 95% confidence interval for the values estimated for the 24-hour RDII and the peak-hour RDII, respectively. Sixty-nine flow monitoring locations (including 1,130 rainfall events) were analyzed with the Nashville Standardized Procedure. The mean for the linear correlation r value was 87% for 24-hour RDI/I, and 82% for peak-hour projections. The mean 95% confidence interval values (expressed as a % of the predicted value) were 34% and 45% respectively for 24- hour and peak-hour results. These statistical tests can also provide a means for comparing the worthiness of different analytical methods for estimating RDI/I.

Keywords: CMOM; I/I analysis; RDI/I; RTK; design flow rate; flow monitoring; flow projection; infiltration/inflow; sewer capacity

Document Type: Research Article


Publication date: January 1, 2010

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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