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Influence of Density of Large Stems on the Blocking Probability at Spillways

Author(s): P. Furlan; M. Pfister; J. Matos; A. J. Schleiss

Linked Author(s): Anton J. Schleiss, Michael Pfister, Jorge Matos

Keywords: Large wood; Blocking probability; Spillway inlet; Logistic regression; Density

Abstract: Dam safety is strongly linked to the probability of occurrence of large floods. Floods can transport large wood (LW) into reservoirs and towards water release structures such as spillways. Due to blocking and clogging, LW may significantly influence the discharge capacity of spillways and thus result in a dangerous rise of the water level in the reservoir. For a better assessment of the related risk, the behaviour of LW in contact with hydraulic structures has to be known. Thus, the understanding of LW blockage processes at the spillway and the resulting water level rise in the reservoir is important for the safety evaluation of a dam. The aim of the present study is to describe how LW characteristics can influence blocking probabilities at a spillway inlet equipped with piers. By investigating the parameters linked to LW blockage, like slenderness and density or different hydraulic conditions and transport scenarios, it becomes possible to quantify the behaviour and consequences of LW interactions with spillways. Through systematic laboratory experiments, the influence of LW density on blocking probabilities of individual stems was analysed. Experiments were conducted for reservoir approach flow type, implying small magnitudes of reservoir flow velocity. The results were considered statistically as Bernoulli experiments and the methodology applied was a logistic regression. For the combinations explored, a relation between blocking probability and density, among other parameters, was studied.


Year: 2018

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