Data Files for the Development of Regression Equations for the Estimation of the Magnitude and Frequency of Floods at Rural, Unregulated Gaged and Ungaged Streams in Puerto Rico through Water Year 2017 (ver. 1.1, September 2021)

Estimates of the magnitude of peak-flows were updated for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent chance exceedance levels for 91 rural, unregulated streamgaging stations on the main island of Puerto Rico. These stations required 10 or more years of annual peak-flow record, using data to 2017, for inclusion in the study. The magnitude and frequency of floods at selected streamgages in Puerto Rico were estimated using the U.S. Geological Survey PeakFQ program and updated methods outlined in Bulletin 17C (England and others, 2018). Regional regression equations were calculated to estimate flood frequency statistics at ungaged locations using selected basin characteristics as explanatory variables. These variables were determined from digital spatial datasets and geographic information systems using the most recent data available, as referenced in the U.S. Geological Survey web application, StreamStats, and published in Kolb and Ryan (2021). A generalized least squares procedure in the U.S. Geological Survey program, WREG, was used to account for cross-correlation of sites and develop the final regional regression equations using drainage area as the only explanatory variable. Two separate regions were defined for regression equation use in this study to minimize residuals. References Cited: England J.F., Jr., Cohn, T.A., Faber, B.A., Stedinger,J.R., Thomas,W.O.,Jr., Veilleux,A.G., Kiang,J.E., and Mason,R.R., Jr., 2018, Guidelines for determining flood flow frequency -Bulletin 17C: U.S. Geological Survey Techniques and Methods, book 4, chap. B5, 148p., https://doi.org/10.3133/tm4B5. Kolb, K.R., and Ryan, P.J., 2021, Basin Characteristic Rasters for Puerto Rico StreamStats, 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9HK9SSQ.