Trends in hydrologic prediction for the design of hydraulic projects

Estimation and prediction of runoff and related design discharges under past and future conditions are key elements for the design of flood defense, watercourse demarcation, urban stormwater, road drainage systems. Ministry of Infrastructure and Transportation, Greece, is in the process of updating design guidelines for hydraulic projects, including hydrologic computations. Special Secretariat for Water, Ministry of the Environment and Energy, for the implementation of 2007/60/EU Floods Directive published idf relations for all areas of Greece, based on advanced methodology. Prediction, especially for ungaged areas is difficult and involves high uncertainty. Advanced computer capabilities provided by GIS and hydrologic modeling software facilitate computations and allow for the comparison of results by different approaches. However, still many empirical relations are included, based on limited field data developed decades ago. Internationally there is a trend towards risk-based design. The basic form of risk-based optimisation is economic optimisation aiming at minimisation of the lifetime cost of the project. USACE issued (2016) a guidance for incorporating climate change impacts to inland hydrology in civil works studies, requiring qualitative analysis, whereas for changes other than climate that affect hydrology, reference is made to guidance dated to 1994. Economic and climate change projections also involve high uncertainty.