Description

Many practical engineering problems that we encounter in spatial planning, especially in reference to site selection and placement of various structures and in providing their protection against floods, require in the planning process also information about design discharges or design hydrographs. Estimating design discharges or design hydrographs, however, is not always straightforward. In Slovenian hydrotechnical/water management practice, simple empirical equations are still very often used to determine design discharges. The use of flood frequency analyses, which give the relationship between design discharges and return periods based on measured data, gives us only peak discharge values, rather than other characteristics of flood waves, which are necessary for reliable results of hydraulic models and further engineering applications. The use of calibrated and verified hydrological models or procedures of regionalization of design discharges or design hydrographs is still rare in Slovenian hydrological practice. In addition, uncertainty or at least variability due to the present uncertainties is almost never taken into account when estimating design discharges or design hydrographs. Furthermore, we should not forget climate change. Accordingly, it is necessary to introduce more advanced hydrological methods for estimating design discharges and design hydrographs into Slovenian water management practice, which will reduce uncertainties in the design process.

The main goal of this research project is therefore to define the methodology for estimating the flood waves of rivers (i.e. design hydrographs) in Slovenia based on experience, practices, and relevant literature. An appropriate methodology for estimating the design discharges or design hydrographs will be proposed for the case when measured flow data are available, as well as for the case when they are not (e.g. sub-basins, upstream of the water gauging station), i.e. based on the measured discharges/hydrographs at water gauging stations as well as based on design precipitation values using a calibrated and verified hydrological model. In both cases, the methodology for estimating uncertainty or natural variability will be presented. All steps of the methodology will be presented using practical examples. The proposed methodology will be presented to professional institutions, operating in the field of hydrology in Slovenia. The proposed methodology will support the profession in estimating the design discharges and design hydrographs, which are essential for more reliable results of hydraulic models as well as appropriate spatial planning and adopting of measures to reduce flood risk.

Project goals

The main goal of this project is to develop a methodology for determining design hydrographs based on extreme precipitation events. Additionally, the methodology for determining design hydrographs will be prepared based on measured discharge data. It will be harmonized with stakeholders in Slovenia. The methodology with practical examples will be presented at workshops, the number of which will be adjusted to the expressed interest. Methodological guidelines will be prepared in the form of a report, which can become an expert recommendation or some kind of a regulation (e.g., a guideline).

Project work packages

• Work package 1 (WP1): Review of relevant national and international literature
  Duration: Months 1–3
• Work package 2 (WP2): Development of a methodology for determining design hydrographs
  • WT2.1: Development of a methodology for determining design hydrographs based on measured discharge data
    Duration: Months 4–9
  • WT2.2: Development of a methodology for determining design hydrographs based on precipitation data
    Duration: Months 4–12
• Work package 3 (WP3): Methodology harmonization, synthesis, and dissemination
  Duration: Months 13–18