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Dam Incidents and Failures – Cases in the Czech Republic
(Sciendo, 2023-03-31) Kotaška, Stanislav; Říha, Jaromír
Dam incidents and failures mainly occur during extreme floods. In the Czech Republic (CR), large-scale regional floods were recorded in different regions in 1985, 1987, 1997, 2002, 2006, 2010, and 2013, while local floods especially occurred in 1991, 1996, 1997, 1998, 2002, 2004, 2005, 2009, and 2010. During these events, numerous incidents and total breaches of small dams were recorded, and a few large dams were also critically endangered, although they were not completely breached. This paper presents a comprehensive summary of incidents and failures affecting small dams in the CR since 1985. The most significant incidents concerning large dams are listed as well. The statistics show that 62 small dams were completely breached and that 350 were seriously damaged over 35 years in the period 1985–2020. The annual frequency amounts to 1.85 collapsed and 10 small damaged dams per year. The most common causes of the complete breaching of dams were overtopping (85 %) and internal erosion (15 %).
Quantification of Groundwater Hazards Related to Fluvial Floods via Groundwater Flow Modelling: A Review
(MDPI, 2023-03-15) Říha, Jaromír; Julínek, Tomáš; Duchan, David
Flood-related issues include the impact of groundwater on flood protection measures and other subsurface structures in a protected area. At the same time, subsurface elements of flood protection structures may significantly influence the natural groundwater regime and affect existing structures during non-flood periods. The paper provides an overview of hazardous factors linked to groundwater and specifies variables for the quantification of related hazards. Appropriate hydraulic groundwater flow models are presented and discussed, and their suitability for the modelling of individual typical problems and for hazard quantification is specified. The use of models and the application of CAD and GIS tools for data pre- and post-processing is mentioned in brief and demonstrated on examples of typical practical situations.
Influence of Rainfall Events and Surface Inclination on Overland and Subsurface Runoff Formation on Low-Permeable Soil
(MDPI, 2022-04-20) Gruchot, Andrzej Tadeusz; Zydroń, Tymoteusz; Walega, Andrzej; Pařílková, Jana; Stanisz, Jacek
This paper presents the results of laboratory tests that allowed us to determine the effect of the soil surface inclination and its initial moisture content on the formation of overland and subsurface runoff. The experiments were carried out for the soil that is commonly present in the southern part of Poland, including the Outer Carpathians. The results of these measurements served as a reference for overland runoff calculations using the Richards model, simplified Green–Ampt model, and the empirical model (MSME). The results of the measurements showed that, for low-permeable soil, overland runoff is the dominant form. It was shown that a slope in the range of 2.5–5.0% does not have a significant effect on the amount of overland runoff, but affects its dynamics. The measurements also showed that the starting time and amount of overland runoff are strictly associated with the initial soil moisture content. High soil moisture content in the period preceding the onset of rainfall causes faster generation and an increase in overland runoff, which is caused by the saturation of the surface layer of the soil. This mechanism was confirmed by the results of calculations using the Richards model and measurements of the electrical resistance of the soil. Theoretical calculations showed that the results of the runoff calculations using the Richards and Green–Ampt models are strongly dependent on the hydraulic properties of the soil adopted for the analysis. It was also demonstrated that the modified MSME model satisfactorily estimates the amount of overland and subsurface runoff, but requires parameter calibration based on existing hydrological data.
Multicriterial analysis used for the optimisation of dike system management
(Chartered Institution of Water and Environmental Management and John Wiley & Sons, 2022-05-20) Duchan, David; Julínek, Tomáš; Říha, Jaromír
Levees are the most frequently used flood protection measure worldwide. In central Europe, they have been built systematically since the beginning of the 19th century. After the extreme regional floods in 1997, 2002 and 2013, the need arose for a more systematic and optimised approach to levee design and management, including the decommissioning of ineffective dike reaches. In this paper, a multicriterial algorithm is presented for the optimisation of levee management. The aspects considered are flood risk, economy, technical conditions, environmental issues and the consistency with general documents and principles in water management. The method is demonstrated via a case study of a levee subsystem in the upper Morava River basin.
The application of a minimum specific energy concept for a fish ladder design
(Polish Academy of Sciences, 2022-05-13) Kubrak, Michal; Smolinski, Blažej; Říha, Jaromír; Kodura, Apoloniusz; Popielski, Pawel; Jablonski, Kamil
Structural solutions in terms of fish ladders and the use of natural materials to construct them often raise concerns regarding the possibility of using the standard calculation methods. The fish ladder being designed on the Wisłok river consists of three pools, separated from each other by baffles made of rock boulders. The purpose of this study was to analyze water surface profiles for fish ladder at specific values of flow rates. The paper presents the results of hydraulic calculations under the conditions of constant flow rate based on the concept of a minimum specific energy. According to this method, water flow through boulders is critical. Thus, it does not take into account head losses, which are hard to estimate and which are the integral part of typical calculation methods, e.g. the use of equations to determine the flow rate of a weir. An additional advantage of this method is that there is no need to assume the flow pattern of one specific weir. Verification calculations of the water depths were conducted using the HEC–RAS software, under an assumption of an one-dimensional steady water flow. Water depths in the fish ladder, calculated using both methods, were similar, despite the adopted different calculation concepts, and can be used in ichthyologic analyses.

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