Analysis of Peak Flow Distribution for Bridge Collapse Sites

Fahmidah U Ashraf,Madeleine M Flint

doi:10.3390/w12010052

Abstract

Bridge collapse risk can be evaluated more rigorously if the hydrologic characteristics of bridge collapse sites are demystified, particularly for peak flows. In this study, forty-two bridge collapse sites were analyzed to find any trend in the peak flows. Flood frequency and other statistical analyses were used to derive peak flow distribution parameters, identify trends linked to flood magnitude and flood behavior (how extreme), quantify the return periods of peak flows, and compare different approaches of flood frequency in deriving the return periods. The results indicate that most of the bridge collapse sites exhibit heavy tail distribution and flood magnitudes that are well consistent when regressed over the drainage area. A comparison of different flood frequency analyses reveals that there is no single approach that is best generally for the dataset studied. These results indicate a commonality in flood behavior (outliers are expected, not random; heavy-tail property) for the collapse dataset studied and provides some basis for extending the findings obtained for the 42 collapsed bridges to other sites to assess the risk of future collapses.

Highlights

The common causes categorized for bridge collapses in the USA, as recorded in New York StateDepartment of Transportation (NYSDOT) database, are hydraulic, collision, overload, deterioration, geotechnical, nature, and other [1], with 62.23% of over-water bridge collapses corresponding to hydraulic events, 6.9% to collision, 11.33% to overload, 9.03% to deterioration, 1.48% to geotechnical, 3.28% to nature, and 5.75% to other [1]
To flow attain the objectives, this paper presents an trends linked to flood magnitude and flood behavior, and (3) to compare different approaches in analysis of the derived generalized extreme value distribution (GEV) distribution parameters for 42 bridge collapse sites (Figure 1) and deriving return periods for bridge collapse sites
GEV parameters were analyzed to check whether the collapse sites were consistent when regressed on the drainage area

Summary

Introduction

The common causes categorized for bridge collapses in the USA, as recorded in New York State. In response to flood risk, engineering design primarily aims at determining the magnitude of floods for a predefined return period. The methods to determine the flood magnitude of the design flood vary, with recommended methods including TR-55 [4], Bulletin 17C [5], and StreamStats [6], among several others. Regardless of the types of methods chosen, analyzing peak flow distribution parameters is not a common practice in bridge design procedures. The analysis of peak flow distribution parameters provides some basis to reason formally about the counter-intuitive properties of flood events and to identify trends or commonalities among the critical bridge sites

Methods

Results

Discussion

Conclusion