Faculté des Sciences appliquées
Faculté des Sciences appliquées

Effect on flow conditions of floating debris accumulation at bridges

Dütz, Florence ULiège
Promotor(s) : Erpicum, Sébastien ULiège ; Pirotton, Michel ULiège
Date of defense : 26-Jun-2023/27-Jun-2023 • Permalink :
Title : Effect on flow conditions of floating debris accumulation at bridges
Translated title : [fr] Effet des embâcles au droit des ponts sur les conditions d'écoulement
Author : Dütz, Florence ULiège
Date of defense  : 26-Jun-2023/27-Jun-2023
Advisor(s) : Erpicum, Sébastien ULiège
Pirotton, Michel ULiège
Committee's member(s) : Andrianne, Thomas ULiège
ENGLEBERT, Benjamin 
Language : English
Number of pages : 98
Keywords : [en] Flood
[en] Large wood accumulation
[en] Floating debris
[en] Backwater rise
Discipline(s) : Engineering, computing & technology > Civil engineering
Target public : Researchers
Professionals of domain
Institution(s) : Université de Liège, Liège, Belgique
Degree: Master en ingénieur civil des constructions, à finalité spécialisée en "civil engineering"
Faculty: Master thesis of the Faculté des Sciences appliquées


[en] This work is related to the EMfloodResilience project of the Interreg Euregio Meuse-Rhine
project. The main goal is to study the effect of flow conditions on the consequences of floating
debris accumulation at bridges.
Therefore, an experimental campaign was carried out in the Engineering Hydraulics Laboratory of the University of Liège. Two bridge geometries are investigated as well as two different
mixtures of debris and 10 flow conditions characterized by an initial water depth h0 and an
initial Froude number F r0.
The observed accumulation formation process are in agreement with those described in the
literature (Schmocker and Hager, 2013). The accumulation process takes place in 2 phases.
The initial debris accumulation during which the debris accumulate vertically along the pier(s)
and the formation of a debris carpet, during which floating debris accumulates horizontally on
the surface.
The experiments have shown that water depth increases with the volume of debris accumulated at the bridge. Once a certain volume of debris is reached, the water depth barely rises at
The number of bridge piers does not have a big impact on the flow conditions nor on the
debris accumulation. Indeed, although a two pier bridge causes a longer accumulation than a
one pier bridge, the effect on the backwater rise could not be distinguished between the two
geometries. As for the debris composition, it has a significant impact on the accumulation
formation and the backwater rise. The initial Froude number F r0 of the flow has a significant
effect on both the accumulation structure and the flow conditions. The larger the Froude number, the shorter the accumulation. As a result, the accumulation is more compact and blocks
more water, leading to a greater backwater rise.
The relative carpet length and the relative flow depth at the end of the test are linked to the
Froude number with some fit equations The effect of Froude number on accumulation length
differs according to initial water depth and debris mixtures, whereas the effect of Froude on
water height depends very little on debris composition (if at all). The influence of the initial
water depth depends on the position of the bridge deck in relation to the water surface. For a h0
under the deck, it could be concluded that the higher water depth generated higher backwater
The evolution of water depth as a function of accumulation volume can be approximated
by a power law. To obtain a law that does not depend on scale, the normalization proposed
by Schalko et al., 2019a (21) was adapted to the present case. From this law, a characteristic
volume, responsible for the primary backwater rise, can be deduced. For each Froude, bridge
geometry and debris composition, a characteristic volume was determined independently of the
water level.



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  • Dütz, Florence ULiège Université de Liège > Master ingé. civ. constr., fin.


Committee's member(s)

  • Andrianne, Thomas ULiège Université de Liège - ULiège > Département d'aérospatiale et mécanique > Interactions Fluide-Structure - Aérodynamique expérimentale
    ORBi View his publications on ORBi
  • ENGLEBERT, Benjamin
  • Total number of views 63
  • Total number of downloads 117

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