9625685 Salas In view of several recent severe weather events, such as the 1993 Mississippi River floods and the 1995 Rhine River floods, this project will re-examine the design criteria of hydraulic structures for withstanding extreme hydrologic episodes and will re-evaluate the capacity of these structures, such as levees and spillways, for managing excesses or scarcity of water. The research project will analyze the concepts and the computations used to determine return periods and risk of failure for complex hydrological processes involving time-dependence nd non- stationarity. Both extremes of floods and droughts will be examined including uncertainties of estimates. The stochastic models to be used will remove these constraints and actual data will be used in the analytical and computer simulation work. Results from this research will make a significant contribution to the management of flood risk and drought episodes. ***