Analysis considering a range of flood scenarios, as opposed to a single 100-year threshold, could be more robust and accurate about vulnerability of bridges, according to a study.<\/p>\n
\nCurrent risk assessments in the US assume that bridges may collapse when a 100-year flood, a streamflow with one per cent probability of being exceeded in any given year, or 63 per cent over the course of a century occurs, Xinhua news agency reported on Saturday.<\/p>\n
This underestimates risk, according to authors of a paper published in the Journal of Infrastructure Systems, because it fails to capture the full range of stream flow conditions that can cause bridge collapse.<\/p>\n
The researchers in their analysis considered the full variability of floods that could cause collapse, as opposed to the 100-year approach, thus identifying a greater sensitivity to changes in the underlying frequency of flooding.<\/p>\n
Of the 35 bridges analysed, 23 were estimated to have collapsed during a water flow of lesser intensity than a 100-year flood level.<\/p>\n
The authors note that a primary reason for these lower flow collapses is the fact that most of those collapsed bridges were built before modern design standards.<\/p>\n
Because most US bridges, along with most infrastructure, pre-date the modern design standards, the results highlight a more general risk that extreme climate events pose to US infrastructure.<\/p>\n