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Spectral analysis of oscillatory wind wave parameters in fetch-limited deep-water conditions at a small reservoir and their prediction: Case Study of the Hulín Reservoir in the Czech Republic
(Sciendo, 2024-02-01) Kotaška, Stanislav; Duchan, David; Pelikán, Petr; Špano, Miroslav
The dams and banks of small water reservoirs face significant erosion from wind-generated oscillatory waves. Proper design of structure height is crucial to protect such banks against erosion, considering the maximum characteristics of wind waves. Long-term measurements at the Hulín reservoir revealed that the wave spectrum aligns best with the Bretschneider type. This spectrum serves as a basis for simulating oscillatory waves and their impact on shore protection structure design. Empirical models were evaluated using wind and wave data from Hulín reservoir in the Czech Republic. The measured wind speeds attained a maximum of 8 m/s, and wave heights reached up to 15 cm. The Bretschneider (SMB) empirical formula provided the most accurate estimation of wave height (Hm0), with an average underestimate of RMSE = 0.038 m. On the other hand, Wilson revisited (WIL rev.) performed less effectively, with an average RMSE = 0.304 m. For wave period (T) estimation, Bretschneider (SMB) yielded the best results, with an average RMSE = 0.062 s. Conversely, Wilson revisited (WIL rev.) showed poorer performance, with an average underestimate of RMSE = 2.196 s. The discrepancy between the empirical formulas and measured values, particularly in underestimating Hm0, can be attributed to inaccurate determination of fetch length and wind speed.
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.

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