Towards development of the methodology for the design hydrograph definition including stochastic simulations in Slovenia, Europe

Engineers are often required to derive design peak discharges and hydrographs that are needed for the planning, design and construction of the hydro-technical structures such as dikes, dams or preparation of the flood risk or hazard maps. There are numerous options available for the design peak discharge and hydrograph estimation ranging from simple empirical equations to complex rainfall-runoff models including stochastic rainfall simulators. Additionally, rainfall-runoff model parameters can be estimated using a variety of methods depending on the availability and quality of data. However, such methods are often too complex or time consuming to be used in practice. Therefore, the knowledge gap between theoretical hydrology and practical hydrological applications can be very large in some cases. Thus, engineers are often using very simple methods that do not account for the uncertainty in the design values estimation. Additionally, they often do not use all available data (e.g., discharge, precipitation).

Moreover, a step forward is also needed in the process of the preparation of the flood hazard and risk maps that have been prepared across Europe based on requirements of the EU Flood Directive (Directive 2007/60/60). In order to follow good practices in some other fields (e.g., earthquake engineering), where probabilistic approach is used in the design, a similar methodology would need to be developed for the preparation of flood maps taking into account stochastic nature of the hydrological processes.

Therefore, a robust methodology that takes into account the latest state-of-the-art research findings and knowledge is needed to guide engineers in the process of the design discharge and hydrograph definition. Such methodology is currently lacking in Slovenia, where complexity of hydrological estimations is often on lower level compared to the hydraulic calculations conducted. This contribution presents recent work carried out in relation to the definition of the methodology for the design peak discharge and hydrograph calculation in case of gauged and ungauged catchments in Slovenia. The methodology will also include guidelines related to the stochastic simulations and definition of multiple design hydrographs that could be used to derive probabilistic flood risk maps.

We acknowledge the financial support from the Slovenian Research Agency (grant: V2-2137).