Bridge pier shape influence on wood accumulation: Outcomes from flume experiments and numerical modelling

Section: Introductionmentioning

confidence: 70%

An Experimental and Numerical Approach to Modeling Large Wood Displacement in Rivers

Panici

2021

“…However, in our experiments cylindrical artificial stems were used, under different approach flow conditions, so conclusions about the influence of irregular stem geometry cannot be drawn. Based on the work done in De Cicco et al (2016Cicco et al ( , 2020, where they investigated the effect of the pier shape in the accumulation of LW at bridges for river approach flows, it was concluded that the round nose piers are less prone to LW blockage when compared to other geometries. On the contrary, in Schalko et al (2020) they concluded that only a minor effect was observed for bridge pier shapes in terms of blocking probability.…”

Section: Comparison With Other Studiesmentioning

confidence: 99%

“…The classification of LW includes stems longer than 1 m and with a diameter larger than 0.10 m (Braudrick et al., 1997; Ruiz‐Villanueva, Piégay, Gurnell, et al., 2016; Wohl et al., 2016). The transport of LW can induce dangerous obstructions at hydraulic infrastructures like bridges, weirs and spillways during floods (Allen et al., 2014; Bénet et al., 2021; De Cicco et al., 2016, 2020; Gschnitzer et al., 2017; Hartford et al., 2016; Hartlieb, 2012; Iroumé et al., 2015; Panici & de Almeida, 2018; Pfister, Capobianco, et al., 2013; Piton et al., 2020; Schalko et al., 2020; Schmocker & Hager, 2011).…”

Section: Introductionmentioning

confidence: 99%

Blockage Probability Modeling of Large Wood at Reservoir Spillways With Piers

Furlan

Pfister

Matos

et al. 2021

Large wood increases the morphological and hydraulic complexity of rivers, yet it may block and modify the flood discharge capacity of hydraulic structures. To assess the related risk, blockage probability estimation for hydraulic structures such as reservoir spillways is needed. This work presents unstudied parameters for blockage of large wood with a reservoir‐type approach flow, where the inflow velocity has a negligible magnitude. Experiments were conducted in a channel with an ogee crested spillway equipped with piers, representing a commonly used hydraulic structure. Artificial stems were used to systematically evaluate the influence of stem length and stem draft on the blocking process. Different hydraulic conditions were evaluated by changing the water level in the reservoir. The head at the spillway crest with respect to stem draft was found to be a key parameter for blockage probability estimation at a spillway. Additionally, stem length was related to the bay width in the estimation of blockage. Larger heads tend to reduce the blocking probability of large wood, for a given stem draft, while increasing the relative stem length tends to increase the blocking probability. A logistic regression model is provided to estimate large wood blockage probability at ogee crested spillways with piers. Finally, recommendations for engineering practice are presented.

“…Some authors focused their attention on the mechanisms of instability of the emerging rigid vegetation when major flood events occur (Calvani et al., 2019; Francalanci et al., 2020; Miyamoto & Kimura, 2016; Tanaka & Yagisawa, 2009). Other authors investigated the dynamics of mobilization and transport of woody debris already present in the riverbed (Bocchiola at al., 2008; Persi et al., 2016, 2018, 2019; Ruiz‐Villanueva et al., 2016; Sibilla et al., 2020; Zischg et al., 2018), the risk and the probability of wood accumulation at bridge piers and deck (Diehl, 1997; Panici et al., 2020; Shalko et al., 2020a), the geometric parameters that contribute to worsen such an accumulation (De Cicco et al., 2015), their influences on the stability of the accumulations (De Cicco et al., 2020; Panici & de Almeida, 2018) and the engineering strategies to reduce the occurrence of such situations (Rossi & Armanini, 2019; Schalko et al., 2020b; Schmocker & Weitbrecht, 2013). The entrapment probability increases if the bridge has prominent abutments, low freeboard, and piers in the riverbed, but also in the absence of piers and in conditions of a supercritical flow if the bridge is already partially occluded, or in presence of a subcritical flow if the entrance is initially not dammed (see Gschnitzer et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

Roughness‐Based Method for Simulating Hydraulic Consequences of Both Woody Debris Clogging and Breakage at Bridges in Basin‐Scale Flood Modeling

Macchione

Lombardo

2021

Obstructions at bridge can exacerbate flood hazard: when woody debris occlude a bridge, backwater increases, and sometimes a temporary reservoir can form. If the condition for the collapse of the jam exists, the phenomenon can evolve into a dam break flow resulting in an increase in downstream discharge or a steepening in the flow hydrograph. A rigorous description of backwater formed by debris at the bridge, and more generally of the interaction between flood and structure, is still a challenge and only few studies focus on the breakage phase and its consequence on flood dynamic. Unfortunately, analyzing the hydraulics of so many localized situations within a large area in detail would involve considerable modeling and calculation costs. Therefore, treatment methods are desirable that provide correct results in terms of the reference hydraulic variables for assessing the hazard without the need to model extremely local phenomena. The purpose of this study is to evaluate the possibility to reproduce an observed or estimated backwater by the use of an equivalent roughness at the place of the bridge and simulate the breakage phase by a sudden variation of its value. The method, applied to the numerical reconstruction of the experimental tests of dam break performed by the Waterways Experiment Station in 1961, has provided results that overlap well with the experimental values. Furthermore, it was applied to the reconstruction of the historical flood occurred in the Soverato river (Calabria, Italy). It did not require local grid refinement and provided results faithful to flood marks.