Design envelopes estimation by hydrological subregion

Abstract

Design flood estimation in ungauged watersheds is very common. The use of envelope curves with return periods estimated by hydrological subregion is perhaps the simplest regional method for obtaining the necessary predictions. This work describes the 6 steps of the suggested procedure in detail: (1) subregion definition; (2) critical screening of the data; (3) statistical verification of the data; (4) subregional homogeneity verification; (5) prediction estimates, and; (6) calculation of fit coefficients for the envelope curves design. Creager, Lowry and Francou-Rodier envelope curves were utilized. The application of the above procedure is also explained in some detail for 5 Mexican subregions. Results are analyzed and conclusions are formulated that indicate the advantages of working by subregion and the ease of verifying reliable results when they are consistent.