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

Abstract

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.

Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

“…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.…”

The Sustainable Development of Bridges in China: Collapse Cause Analysis, Existing Management Dilemmas and Potential Solutions

“…Flow conditions vary in different regions, making flooding a major cause of damage to highway and railway bridges. Bridge collapses due to floods are not uncommon, and frequent flood disasters, inherent deficiencies in foundation design, and human-induced changes in riverbeds are the primary culprits [57][58][59][60][61]. Data maintained by The New York State Department of Transportation show that, between 1992 and 2014, hydraulic-induced failure caused 55.4% of the 428 bridge collapses in their database [62], and a historical analysis of hydraulic bridge collapses is performed to check the relationship between bridge collapses and flood frequency or intensity [63].…”