Regional envelope curves for the state of Ceará: a tool for verification of hydrological dam safety

Envoltórias regionais de cheias milenares e decamilenares para o estado do Ceará: ferramenta para verificação da segurança hidrológica de barragens

ABSTRACT

Envelope curves are important tools for preliminary evaluation of design floods, for sizing hydraulic structures and for checking the design peak discharge in old dams, to verify their hydrological safety. These curves, associated with a mathematical equation, determine the upper line that involves the maximum values of the floods associated with the respective basin areas. Envelope curves can be global or regional; maybe relative to maximum recorded floods or certain return periods. This paper presents a review of the various envelope curves developed in the world and, in addition, applies them to the hydrological conditions of the watersheds in Ceará. Three envelope curves widely used in the literature were tested. Based on the estimation of new regional parameters for Ceará, envelope curves for floods with Tr equal to 1.000 and 10.000 years were constructed for the State. For developing the envelope curves, 43 hydrological dams’ projects, designed by hydrological techniques adopted by state water resources institutions, were investigated.

Keywords:
Envelope curves; Peak discharges; Francou-Rodier; Creager; Castellarin; Dam safety