Abstract
Failures of small dams can pose a serious threat to people and property even if the size of the schemes is relatively low. In many cases, small dams are situated in a cascade along streams, meaning that the failure of the uppermost dam may cause the dams downstream to fail. In this paper, a cascade of three small reservoirs, Lichnov II (14.6 m high), Lichnov III (10 m high), and Pocheň (8.5 m high), is the subject of the dam break analyses carried out via various methods such as empirical formulae, analogy, and hydraulic modeling. The dam-break flood routing was simulated using a shallow water flow hydraulic model. The simulations confirm that the attenuation effect of the peak discharge is governed by the flood volume, slope, and morphology of the floodplain and increases with the distance from the breached dam following an approximately exponential trend. When estimating peak discharge, empirical formulae derived for a single dam break should be applied carefully as they may underestimate the peak outflow by up to 10% in the case of a dam cascade. The attenuation volume of small reservoirs is small when compared to the flood volume, meaning that the attenuation of the peak discharge usually varies between 5–10%.
Highlights
Every dam represents a certain threat due to the possibility of its failure, which may lead to a dam-break flood in the area downstream
The simulation of a dam break in a cascade consists of two basic procedures, namely single damThe simulation of a dam break in a cascade consists of two basic procedures, namely single dambreak analysis (Sections 3.1 to 3.3), and the analysis of the dam-break-induced flood between the break analysis (Sections 3.1 to 3.3), and the analysis of the dam-break-induced flood between the dams (Section 3.4)
When used for peak discharge estimation, empirical formulae derived for a single dam break should be applied carefully, as they may underestimate the peak outflow by up to 10% in the case of a dam cascade
Summary
Every dam represents a certain threat due to the possibility of its failure, which may lead to a dam-break flood in the area downstream. Statistics show that the most frequent causes of earth-fill dam failures are overtopping and internal erosion [1,2,3]. The safety of small dams, ponds, and dry reservoirs is still topical. In the Czech Republic, there are about 20,000 small dams. During extreme floods in 1997, 2002, and 2010, dozens of collapsed small dams were reported [4]. Dam break studies, including dam-break flood propagation modeling are carried out for systems of small dams.
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