Quantification of Modelling Uncertainties in Bridge Scour Risk Assessment under Multiple Flood Events

Local scour is a dynamic process evolving during the lifetime of bridges as a result of the changes in hydrologic and hydraulic conditions. Current approaches for scour risk assessment are generally based on the evaluation of the equilibrium scour depth for a flood event with a prefixed return period. The temporal evolution of the bridge-pier scour process is usually disregarded, by assuming that equilibrium conditions are always attained, regardless of the flood properties. However, recent studies have highlighted the importance of accounting for the contribution of multiple flood events and their exact hydrograph shape. This study aims at quantifying the epistemic uncertainty related to the modelling of the temporal evolution of scour under multiple consecutive flood events in clear-water conditions. A simple numerical case study is considered, using a Markovian framework to describe probabilistically the progression of scour. Well-known time-dependent scour models are used to estimate the temporal evolution of the scour-depth under each flood hydrograph, and the scour estimates are compared with those obtained using widely employed equilibrium scour formulas. Results show that the expected scour depth is influenced by the parameters used to describe the flood hydrograph and that the probability distribution of the scour depth is highly sensitive to the choice of the time-dependent scour model. The uncertainty in the scour estimation stemming from the formula adopted in this study for describing the temporal evolution of the scour depth can be higher than those related to the formula adopted for equilibrium scour.

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Experimental study of clear-water contraction scour

Water Science & Technology Water Supply ◽

10.2166/ws.2020.014 ◽

2020 ◽

Vol 20 (3) ◽

pp. 943-952 ◽

Cited By ~ 4

Author(s):

Ravindra Kumar Singh ◽

Manish Pandey ◽

Jaan H. Pu ◽

Srinivas Pasupuleti ◽

Vasanta G. Kumar Villuri

Keyword(s):

Experimental Study ◽

Reasonable Agreement ◽

Time Dependent ◽

Scour Depth ◽

Clear Water ◽

Equilibrium Conditions ◽

Bridge Abutment ◽

Water Conditions ◽

Contraction Scour ◽

Equilibrium Scour Depth

Abstract In this paper, experimental results of clear-water scour on a sand bed under short contractions were studied. Sequences of test runs were performed under clear-water conditions for three different contraction ratios. The outcomes of the experiments were employed to define the effects of various parameters on equilibrium scour depth under clear-water scour conditions. In this work, the precision of three maximum scour depth equations was tested from previous studies for contraction scour cases. Two new analytical equations were proposed to calculate time-dependent scour depth and maximum scour at equilibrium conditions, respectively, from the study. The proposed equations were validated using measurements from the present study as well as from previous literature, and the equations show a reasonable agreement between measured and computed values of scour depth under clear-water conditions in short contraction. The presented equations can be used for studying protection of the submerged portion at a bridge abutment or any similar structure.

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Design Floods Considering the Epistemic Uncertainty

Water ◽

10.3390/w13111601 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1601

Author(s):

Radu Drobot ◽

Aurelian Florentin Draghia ◽

Daniel Ciuiu ◽

Romică Trandafir

Keyword(s):

Flood Hazard ◽

Epistemic Uncertainty ◽

Statistical Distributions ◽

Hazard Maps ◽

Design Flood ◽

Flood Hydrograph ◽

Recorded Data ◽

Different Shapes ◽

Significant Spread ◽

Flood Hazard Maps

The Design Flood (DF) concept is an essential tool in designing hydraulic works, defining reservoir operation programs, and identifying reliable flood hazard maps. The purpose of this paper is to present a methodology for deriving a Design Flood hydrograph considering the epistemic uncertainty. Several appropriately identified statistical distributions allow for the acceptable approximation of the frequent values of maximum discharges or flood volumes, and display a significant spread for their medium/low Probabilities of Exceedance (PE). The referred scattering, as a consequence of epistemic uncertainty, defines an area of uncertainty for both recorded data and extrapolated values. In considering the upper and lower values of the uncertainty intervals as limits for maximum discharges and flood volumes, and by further combining them compatibly, a set of DFs as completely defined hydrographs with different shapes result for each PE. The herein proposed procedure defines both uni-modal and multi-modal DFs. Subsequently, such DFs help water managers in examining and establishing tailored approaches for a variety of input hydrographs, which might be typically generated in river basins.

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Estimating Equilibrium Scour Depth at Cylindrical Piers in Experimental Studies

Journal of Hydraulic Engineering ◽

10.1061/(asce)hy.1943-7900.0000410 ◽

2011 ◽

Vol 137 (9) ◽

pp. 1089-1093 ◽

Cited By ~ 27

Author(s):

Gonzalo Simarro ◽

Cristina M. S. Fael ◽

António H. Cardoso

Keyword(s):

Experimental Studies ◽

Scour Depth ◽

Equilibrium Scour Depth

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Semantic model for flood management

Journal of Hydroinformatics ◽

10.2166/hydro.2012.064 ◽

2012 ◽

Vol 14 (4) ◽

pp. 918-936 ◽

Cited By ~ 4

Author(s):

Julián Garrido ◽

Ignacio Requena ◽

Stefano Mambretti

Keyword(s):

Risk Assessment ◽

Conceptual Framework ◽

Environmental Assessment ◽

Risk Evaluation ◽

Evaluation Process ◽

Flood Management ◽

Semantic Model ◽

Effective Management ◽

Flood Events ◽

Qualified Personnel

Risk assessment involves the study of vulnerability and hazards. When focused on flood events, such an analysis should evidently include the theoretical and practical study of floods and their behavior. Nevertheless, risk assessment is not useful if the results are not subsequently used for more effective management and planning by local authorities and qualified personnel. The risk evaluation process is composed of a set of actions, each of which requires different inputs. In fact, the results of one action are used as the input for another. This paper describes a semantic model for the study and management of floods with a view to elaborating a conceptual framework and designing a knowledge base. The model is based on the environmental assessment ontology and demonstrates how a brief ontology can be generated.

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Methodology for risk assessment of flash flood events due to climate and land use changes

Comprehensive Flood Risk Management ◽

10.1201/b13715-6 ◽

2012 ◽

Author(s):

M Velasco ◽

A Cabello ◽

I Escaler ◽

J Barredo ◽

A Barrera-Escoda

Keyword(s):

Risk Assessment ◽

Land Use ◽

Flash Flood ◽

Land Use Changes ◽

Flood Events

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Understanding epistemic uncertainty in large-scale coastal flood risk assessment for present and future climates

10.5194/nhess-2018-127 ◽

2018 ◽

Cited By ~ 3

Author(s):

Michalis I. Vousdoukas ◽

Dimitrios Bouziotas ◽

Alessio Giardino ◽

Laurens M. Bouwer ◽

Evangelos Voukouvalas ◽

...

Keyword(s):

Climate Change ◽

Risk Assessment ◽

Flood Risk ◽

Large Scale ◽

Epistemic Uncertainty ◽

Coastal Protection ◽

Flood Risk Assessment ◽

Coastal Flood ◽

Coastal Flood Risk ◽

The Impact

Abstract. An upscaling of flood risk assessment frameworks beyond regional and national scales has taken place during recent years, with a number of large-scale models emerging as tools for hotspot identification, support for international policy-making and harmonization of climate change adaptation strategies. There is, however, limited insight on the scaling effects and structural limitations of flood risk models and, therefore, the underlying uncertainty. In light of this, we examine key sources of epistemic uncertainty in the Coastal Flood Risk (CFR) modelling chain: (i) the inclusion and interaction of different hydraulic components leading to extreme sea-level (ESL); (ii) inundation modelling; (iii) the underlying uncertainty in the Digital Elevation Model (DEM); (iv) flood defence information; (v) the assumptions behind the use of depth-damage functions that express vulnerability; and (vi) different climate change projections. The impact of these uncertainties to estimated Expected Annual Damage (EAD) for present and future climates is evaluated in a dual case study in Faro, Portugal and in the Iberian Peninsula. The ranking of the uncertainty factors varies among the different case studies, baseline CFR estimates, as well as their absolute/relative changes. We find that uncertainty from ESL contributions, and in particular the way waves are treated, can be higher than the uncertainty of the two greenhouse gas emission projections and six climate models that are used. Of comparable importance is the quality of information on coastal protection levels and DEM information. In the absence of large-extent datasets with sufficient resolution and accuracy the latter two factors are the main bottlenecks in terms of large-scale CFR assessment quality.

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Live wildlife trade in markets - a scoping review to inform risk assessment of emerging infectious diseases

10.1101/2021.09.13.21263377 ◽

2021 ◽

Author(s):

Victoria J Brookes ◽

Okta Wismandanu ◽

Etih Sudarnika ◽

Justin A Roby ◽

Lynne Hayes ◽

...

Keyword(s):

Risk Assessment ◽

Infectious Diseases ◽

Scoping Review ◽

Epistemic Uncertainty ◽

Mammalian Species ◽

Emerging Infectious Diseases ◽

World Health Organisation ◽

World Health ◽

Wildlife Trade ◽

The Impact

Wet markets are important for food security in many regions worldwide but have come under scrutiny due to their potential role in the emergence of infectious diseases. The sale of live wildlife has been highlighted as a particular risk, and the World Health Organisation has called for the banning of live, wild-caught mammalian species in markets unless risk assessment and effective regulations are in place. Following PRISMA guidelines, we conducted a global scoping review of peer-reviewed information about the sale of live, terrestrial wildlife in markets that are likely to sell fresh food, and collated data about the characteristics of such markets, activities involving live wildlife, the species sold, their purpose, and animal, human, and environmental health risks that were identified. Of the 59 peer-reviewed records within scope, only 25% (n = 14) focussed on disease risks; the rest focused on the impact of wildlife sale on conservation. Although there were some global patterns (for example, the types of markets and purpose of sale of wildlife), there was wide diversity and huge epistemic uncertainty in all aspects associated with live, terrestrial wildlife sale in markets such that the feasibility of accurate assessment of the risk of emerging infectious disease associated with live wildlife trade in markets is limited. Given the value of both wet markets and wildlife trade and the need to support food affordability and accessibility, conservation, public health, and the social and economic aspects of livelihoods of often vulnerable people, there are major information gaps that need to be addressed to develop evidence-based policy in this environment. This review identifies these gaps and provides a foundation from which information for risk assessments can be collected.

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Physical model study of bedrock scour downstream of dams due to spillway plunging jets

Journal of the South African Institution of Civil Engineering ◽

10.17159/2309-8775/2020/v62n3a4 ◽

2020 ◽

Vol 62 (3) ◽

Author(s):

A Bosman ◽

G R Basson

Keyword(s):

Physical Model ◽

Linear Regression Analysis ◽

Scour Depth ◽

Model Study ◽

Fissured Rock ◽

Scour Hole ◽

Plunging Jets ◽

Concrete Blocks ◽

Rock Bed ◽

Equilibrium Scour Depth

The erosive power of a free-falling high-velocity water jet, flowing from a dam spillway, could create a scour hole downstream of the dam, endangering the foundation of the dam. Despite extensive research since the 1950s, there is presently no universally agreed method to predict accurately the equilibrium scour depth caused by plunging jets at dams. These formulae yield a large range of equilibrium scour dimensions. The hydrodynamics of plunging jets and the subsequent scour of a rectangular, horizontal and vertical fissured rock bed were investigated in this study by means of a physical model. Equilibrium scour hole geometries for different fissured dimensions (simulated with rectangular concrete blocks tightly prepacked in a regular rectangular matrix), for a range of flow rates, plunge pool depths, and dam height scenarios were experimentally established with 31 model tests. From the results, non-dimensional formulae for the scour hole geometry were developed using multi-linear regression analysis. The scour depth results from this study were compared to various analytical methods found in literature. The equilibrium scour hole depth established in this study best agrees with that predicted by the Critical Pressure method.

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