Flash floods are becoming a phenomenon that troubles people more and more often in many Slovak under-mountain regions and society needs to deal with these extreme natural events. This article is showing an example of mathematical modeling of flood protection measures in Small Carpathians region. To secure flood protection, detention reservoirs have been proposed, because of their automatic function that is important due to rapid progress of flash floods. As a base for this project a previous work that attempted to reconstruct the flood has been used. HEC-RAS 4.1.0 software package was used for numerical modeling, which includes flood mitigation calculation. Six variants of proposed detention reservoirs were created and checked by a design flood wave that was created according to rainfall with recurrence period of 100 years. All of the proposed detention reservoirs have exact proportions needed to secure flood protection including height of the dam, length of the dam in crest, type and dimension of outlet and dimensions of emergency spillways. The modeling included flood wave passing during several situations-normal function of detention reservoirs, blocked outlet and dam break. This study should be considered as a base for future flood protection project. An extensive terrain survey has been performed in frame of this project.

Drainage channels are artificial multi-functional elements in a landscape, which have their own specific functions. Although they are primarily used for the drainage of water, they can also even be used for an opposite function, i.e. the artificial water supply of specific regions. This article presents an evaluation of infiltration experiments in drainage channels in the southeastern part of Slovakia. These experiments served for the collection of input data for numerical modeling, especially the determination of the soil type and hydraulic conductivity. The methodology of experimental works in the field as well as some basic information about their evaluation is included.

Implemented flood protection measures come to a re-evaluation due to changes in the hydrological situation, due to more recently occurring flash floods whose robustness exceeds the capacity of the measures initially proposed. The problem is the structures constructed on the streams as well as the unpermitted house building on the banks, the pollution of the stream or sedimentation. Case study on small catchment with problems of flash floods in the middle Slovakia was solved. Stream channel capacity was not sufficient for higher flow rates; therefore new flood protection measures were proposed (river bed training, low training walls, detention reservoir). Their efficiency was verified via mathematical modeling.

Ensuring flood protection is a never-ending task, therefore there is always something to improve or add. Nowadays there is a big boom in detention reservoir projecting for smaller river basins in Slovakia. This paper focuses on flood protection proposal for village Vel’ká Lúka located in the central part of Slovakia. The contribution deals with the hydraulic modelling of present state of river Lukavica channel and its capacity and also proposed flood protection measures. According to geodetic survey and flow rate measurements a 5 km long partially calibrated mathematical model of the Lukavica River has been created. For this purpose, the HEC-RAS software has been used. After evaluation of the flow rate capacity through the village, a flood protection measure – detention reservoir – has been proposed using designed flood wave provided by Slovak Hydro-meteorological Institute (SHMI). According to transformation of flood wave computation, specific parameters of necessary flood protection measures were determined.

The goal of the contribution is to present possibilities of comprehensive and complex procedures for proper design of flood protection measures in several parts of Slovakia. The complex approach consisted of mutual integration of results of partial mathematical models – rainfall-runoff model, sewage system model, 1-D hydrodynamic modelling of open channel flow together with partially covered flows, 2-D hydrodynamic modelling of flooding the town residential area. All modelling works were been done in DTM coming from aerial photography or in conditions of detailed morphological and geodetic survey of investigated rivers basins. According to the modelling process appropriate preventive flood protection measures have been designed and afterwards realised in the territory, i.e. detention reservoirs in the mountain region above the urban regions. Designed flood protection measures should store the flood wave volume and mitigate the effect of flush floods on residential areas of small and even larger cities. Several case studies are presented in the contribution all over the Slovak Republic to emphasize the variety of flood wave progress, its reduction in discharge and postponing in time in different hydrological, morphological and geological conditions of mountain regions. Most of the presented proposals of flood protection measures have been projected and some of them have been already realized.