Resumen de Hidrología de paleocrecidas aplicada al cálculo de la Avenida de Diseño y Avenida Máxima de presas

Gerardo Benito Ferrández, Mayte Rico, Andrés Díez Herrero, Yolanda Sánchez Moya, Alfonso Sopeña, Varyl R. Thorndycraft

• Spanish regulations on dam safety recommend the estimation of a return period of 1000 years forthe Design Flood and of 10,000 for the Safety Check Flood. The criteria used for the calculations arebased on Flood Frequency Analysis (FFA) from gauge record data or on the Probable MaximumFlood (PMF) which is the hypothetical maximum of rainfall turned into runoff. The short gaugerecords affords little support for the FFA and for the hypothetical PMF, which in addition to theabsence of a associated probability, limits the utility of these indices for risk-based dam safety decisions. Palaeoflood techniques are a means of directly assessing the probability of extreme floods andtesting the validity of the PMF-based models. In this paper, palaeoflood record was applied to a casestudy in the Cuadalentin river, upstream of the Valdeinfierno reservoir (372 km2) with a spillwaycapacity of 550 m3s-l. (design flood). In addition, available historical flood data was collected.Palaeoflood data and gauge record, were combined for the FFA, using existing methods for the fitting of distribution functions, such as the maximum likelihood. Palaeoflood analysis provides a discharge of 2350 m3s-l for the design flood (1000-yr return period), and 3450 m3s-l for the safetycheck flood (10,000 yr-return period). The discharge estimated by the PMF is 5786 m3s-l, showingan overestimation of this empirical method. Some recommendations for the calculation of the safetycheck flood and design flood are provided which can improve existing legislation on dam safety.