Bregana River Basin: Hydrodynamic Modeling and Analysis of NBS Suitability Within the Reconect Project

Abstract

The Bregana River (Sava River tributary), is a cross-border watercourse and part of its basin is often flooded. The flood events that occurred in 2005., 2014. and 2015. show the distinctive torrential character of the Bregana River. The bursting of the Bregana resulted in the flooding of houses, posing a risk to reinforced embankments and the removal of material. During the flooding of the watercourse, concrete cascades, bridges and culverts were destroyed, asphalt and macadam roads were damaged and the deposited material reduced the flow of the main stream in some locations. Hydrodynamic models were developed for the Bregana basin: 1D and 1D / 2D, which served to better understand the problems, calculate the damage and risk of floods, but also to establish a real-time flood forecasting system. The models were made through the FRISCO1 project, INTERREG Program between Croatia and Slovenia (Kvesic, D. and Ramuscak, R. (2018). FRISCO1, Cross-border cooperation program, Slovenia Croatia 2014–2020 INTERREG V-A, Development of Improved Hydraulic Model for the Cross-border Bregana River Basin – T6.3) & (FRISCO1 Project (2016–2019) INTERREG Slovenia-Croatia (https://frisco-project.eu/en/about-the-project/general-information-on-the-project/ )). Although various flood mitigation measures have been considered so far, such as retention basins, protective walls, riverbed deepening, it is only through the RECONECT project that analyses of the possible application of the NBS (nature-based solutions) have begun. These analyses have shown that building a retention (among other things) would help mitigate floods, but people, nature and water would benefit from these solutions aswell. In the next period of the RECONECT project, the possibilities of an NBS application (and all their benefits)in the Bregana basin will be considered in more detail.