Regional flood frequencies analysis based on the TCEV distribution in Hydrological Region No. 10 (Sinaloa), Mexico

Abstract

Hydraulic works such as reservoirs, dikes, bridges, and urban drainage, are planned, designed, built, and reviewed (the existing) under a hydrological safety, based on the Design Floods. Such estimates of the maximum annual flow associated with low probabilities of exceedance, are called Predictions and are obtained through the so-called frequency analysis of floods. This technique consists of selecting a probability distribution function (PDF), which represents the sample of available flows, and based on such a model prediction is sought. When the record of floods is reduced, unreliable, or does not exist at the site of interest, regional analysis is used; an approach that extends the length of available records to reduce errors in estimates and allows estimating predictions in locations without data. In this study a contrast was made between local and regional predictions; the latter was obtained according to two different methods in the Hydrological Region No. 10 (Sinaloa), Mexico. In the first method, the records of maximum annual flows and their respective dates of occurrence were processed, to define the regions of influence each. For the second method, which is detailed, the same hydrometric information is used and the flood index method, using the TCEV (two-component extreme value) distribution as a regional PDF, is suggested for flow records that were generated by two physically different mechanisms and cannot be separated. The exposed regional method is much simpler and leads to fairly approximate predictions by deficit and more accurate by excess, according to the relative errors evaluated. Therefore, its systematic application is recommended in other hydrological regions of the country.