Mitigation measures for unsteady flow effects on riverbeds during hydropower peaking

Spiller, Stephan Mark; Rüther, Nils; Friedrich, Heide

doi:10.1201/b17133-240

Cited by 1 publication

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“…Aricó et al (2009) have pointed that this may be the case for mild and small bed slopes. Moreover, artificial flood waves, such as dam-break-like waves (Mrokowska et al, 2013), and waves due to hydro-peaking (Shen and Diplas, 2010;Spiller et al, 2014), are of a dynamic character. On the other hand, when the bed slope is large, then the gravity force dominates and the wave is kinematic (Aricó et al, 2009).…”

Section: Formulae For Friction Velocitymentioning

confidence: 99%

Notes on the estimation of resistance to flow during flood wave propagation

Mrokowska¹,

Rowiński²,

Kalinowska³

2014

Preprint

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Abstract. The paper discusses methods of expressing and evaluating resistance to flow in an unsteady flow. Following meaningful trends in hydrological sciences, the paper suggests abandoning, where possible, resistance coefficients in favour of physically based variables such as shear stress and friction velocity. Consequently, an acknowledged method of friction velocity evaluation based on the relations derived from flow equations is examined. The paper presents both a theoretical discussion of various aspects of friction velocity evaluation and the application of the method to field data originating from artificial dam-break flood waves in a small lowland river. As the method is prone to many errors due to the scarcity and the uncertainty of measurement data, the aim of the paper is to provide suggestions on how to apply the method to enhance the correctness of the results. The main steps in applying the method include consideration of the shape of the channel, the type of wave, the method of evaluating the gradient of the flow depth, and the assessment of the uncertainty of the result. Friction velocity and the Manning coefficient are compared in terms of resistance to flow variability during flood wave propagation. It is concluded that the Manning coefficient may be a misleading indicator of the magnitude of resistance in unsteady flow, and to be inferior to physically based variables in such cases.

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