Retrospective Analysis of U.S. Hydraulic Bridge Collapse Sites to Assess HYRISK Performance

Ashraf, Fahmidah U.; Flint, Madeleine M.

doi:10.1061/9780784483466.009

Cited by 3 publications

(4 citation statements)

References 9 publications

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“…Finally, all 30 sites selected for the study are located within the Appalachian Highland physiographic region. The Appalachian Highland region possesses intrinsic risk conditions, including high erosion at bed and bank and/or debris jams [45,49]. In a recent study on 147 collapse sites within the Appalachian Highland region, including the current study sites, it was found that the region exhibits the characteristics of hydrologic heterogeneity [50].…”

Section: Selection Of Sitesmentioning

confidence: 63%

“…Such a result implies that the spatial scale might need to be narrowed down to identify site-specific differences that lead to specific probabilistic distributions, at least for the studied collapse sites. Recent studies on the collapse sites do reveal specific characteristics for the collapse sites within different physiographic regions, including the Appalachian Highland, such as (a) the presence of very high and very low flows [73], (b) debris jams [45,73], (c) high erosion at bed and bank [45,73], (d) the presence of other in-stream structures [45,73], and (e) the removal of vegetation and other human interference [45]. Such site-specific characteristics are typically included in the hydraulic analysis.…”

Section: Discussionmentioning

confidence: 99%

“…Since consistent flow records of the same length and period are difficult to obtain, the approach of using all available data is also being used in risk assessment tools [44]. Several State Departments of Transportation (DOTs) in the U.S. have used the risk assessment tool HyRisk, incorporating available data of different lengths and periods in relation to hydrology, hydraulics, and structure [45]. In the current study, since the hydrological regimes are least affected by human activities, the adopted approach is also similar to the approach of using 'normal', 'quasi-periodicities', or 'potential' cycles for hydrologic analysis [46].…”

Section: Selection Of Sitesmentioning

confidence: 99%

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Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

Ashraf,

Islam

2023

Water

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There is a crucial need for modeling hydrological extremes in order to optimize hydraulic system safety. It is often perceived that the best-fitted distribution accurately captures the intricacies of the hydrological extremes, particularly for the least disturbed watersheds. Thirty collapse sites with the least disturbed watersheds within the Appalachian Highland region in the U.S. are identified and used to test this perception. Goodness-of-fit tests, time series analysis, and comparison of predictor variables are carried out to find out the best-fitted distribution, identify trends and seasonal variation, and assess site variability. The study results are found to be inconclusive and sometimes contradictory; sometimes even complex distribution models do not provide better results. For most sites, the historic peak flow data are best-fitted with multiple distributions, including heavy and light tails. For monthly flow data, seasonal variation and trend cannot be categorized since no definitive, distinct tendency can be identified. When comparing sites best-fitted with a single distribution to sites best-fitted with multiple distributions, significant differences in certain geospatial characteristics are identified. However, these characteristics at the watershed scale are claimed to be less important in predicting the behavior of a flood event. All of these results capture the difficulties and inconsistencies in interpreting the results of hydrologic analysis, potentially reducing the robustness of the hydrologic tools used in the design and risk assessment of bridges.

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Section: Selection Of Sitesmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Selection Of Sitesmentioning

confidence: 99%

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Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

Ashraf,

Islam

2023

Water

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“…Physiographic settings, such as Appalachian Highland, Central Lowland, and Coastal Plain, do possess high erodible beds and/or banks along with other disturbances such as debris jams, backwaters from Bays and/or intensive human interventions (Johnson, 2006; Simon & Rinaldi, 2000). Under such circumstances, the river sections will not be resilient to lower flows as would have been expected, and therefore collapse risk even at low flows (or flows with lower return periods) can be expected (Ashraf & Flint, 2020, 2021). Since all these collapse‐inducing conditions can manifest in a specific trend of hydraulic geometry, as derived for the study sites with limited human interference, certain trends in AHG can be arguably used as a criterion for risk analysis along with certain flow characteristics, such as low return period of heavy tail flows.…”

Section: Discussionmentioning

confidence: 99%

At‐a‐station hydraulic geometry for reaches with bridge collapse events

Ashraf

Spaunhorst

2022

River Research & Apps

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This study explores the at‐a‐station hydraulic geometry (AHG) for reaches with bridge collapse events. Eighteen reaches in Eastern United States, thirteen reaches in Appalachian Highland, and five reaches in Coastal Plain are examined. The methodology applied for retrieving AHG uses LiDAR (Light detection and ranging) data, and the study results are checked for both hydraulic and geomorphic consistency. The resulting data set is composed of five to thirty‐five measurements of water surface width, mean depth, and mean velocity at each of the 181 cross‐sections. The exponents of the AHG relationships vary considerably. Nonetheless, for most of the cross‐sections, width responds more rapidly to changing discharge, and velocity exponents are less than the width and depth exponents combined. Wide shallow channels with highly erodible beds and/or banks, the ability to transport large bed materials, and the ability to attain a super‐critical condition—are the common profile extracted for most of the cross‐sections across all sites. A definitive AHG configuration is found for the sites with the least human interference. Comparatively low variation of bank‐full geometry is also found for the sites with the least human interference. The prevalence of low flows and/or lower return periods of heavy‐tail flows are also exhibited for most of the sites. The study results suggest that the stream channel instability can be reasonably understood and predicted from AHG particularly if human interference is limited within the watershed. These findings have implications not only for the study of the risk of bridge collapse and bridge design but also to characterize instability in a more rigorous and practical way.

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Explaining the Flood Behavior for the Bridge Collapse Sites

Ashraf

Tyralis

Papacharalampous

2022

JMSE

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Given the increasing intensity and frequency of flood events, and the casualties and cost associated with bridge collapse events, explaining the flood behavior for the collapse sites would be of great necessity. In this study, annual peak flows of two hundred and five watersheds, associated with two hundred and ninety-seven collapse sites, are analyzed. Generalized Extreme Value distribution together with other statistical analyses are used to derive and analyze the shape parameters of the distributions which represent the extremeness of flood events. Random forest mechanism is employed in order to identify the predictor variables (and the associated importance levels) for the shape parameters. Peak flows are also classified in order to find the extremes and the associated return periods. The results indicate that most of the bridge collapse sites across different physiographic regions, i.e., Appalachian Highland, Central Lowland, Coastal Plain, and Interior Highlands, exhibit common characteristics such as (a) variation of important predictor variables, (b) human interference, (c) extremeness of flood events similar to the regions with hydrologic heterogeneity, and (d) frequent occurrence of extreme flows. These results indicate a commonality in flood behavior, as stems from specific settings, for the collapse sites studied. The findings instigate the revisiting of the bridge design practices and guidelines and provide some basis to assess the risk of future collapse.

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Retrospective Analysis of U.S. Hydraulic Bridge Collapse Sites to Assess HYRISK Performance

Cited by 3 publications

References 9 publications

Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

At‐a‐station hydraulic geometry for reaches with bridge collapse events

Explaining the Flood Behavior for the Bridge Collapse Sites

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