Details:

Creators:
Webb, Bret M. ; Farmer, Amanda ; Perry, Wes
Webb, Bret M. ; Farmer, Amanda ; Perry, Wes Less -
Corporate Creators:
University of South Alabama. Dept. of Civil Engineering ; Mississippi. Dept. of Transportation
University of South Alabama. Dept. of Civil Engineering ; Mississippi. Dept. of Transportation Less -
Corporate Contributors:
United States. Federal Highway Administration
Subject/TRT Terms:
[+]
Coastal Engineering Disaster Resilience Sea Level Storm Surges Sustainable Development Sustainable Transportation
Publication/ Report Number:
FHWA-HEP-18-042
Resource Type:
Tech Report
Geographical Coverage:
United States ; Mississippi
United States ; Mississippi Less -
Corporate Publisher:
United States. Federal Highway Administration
Abstract:
The storm surge and waves generated by Hurricane Katrina caused widespread damage to built infrastructure in coastal Mississippi and neighboring states. A number of coastal bridges and roadways failed during this event. One such bridge in coastal Mississippi was the Henderson Point connector that carries US HWY 90 over railroad tracks and a small tidal creek. One two-lane span was completely displaced from its bent beams while the adjacent span shifted laterally by a few inches. The causes of the failure were not known before this study began. This particular site was chosen for the pilot project in order to address a key knowledge gap regarding the vulnerability of coastal bridges: the approach embankment and approach spans that pass through critical elevations where damage during extreme storms is likely. This green infrastructure pilot project seeks to develop a solution that addresses this vulnerability while increasing the resilience of the built and natural systems. Multiple hydrodynamic models were used to determine the likely causes of failure at the Henderson Point bridge. A number of conventional gray adaptation solutions and green infrastructure adaptation options were considered in this study. A pair of vegetated berms were selected for evaluation as a green infrastructure solution (Figure ES 1). The berms would eliminate or substantially reduce flow velocities near the bridge abutment and low-elevation approach spans by redirecting flood flows away from those vulnerable elements. Even with a relatively low material cost (~$20,000 not including vegetation), the vegetated berms would reduce the likelihood of bridge span failure during its 50-yr design life from 64% to 39%, by protecting the bridge against the 1% annual chance coastal flood event (current protection level is to the 2% event). There were three significant lessons learned in this pilot project. First, this may be the first known coastal bridge that failed as a result of hydrodynamic drag forces due to flowing water during a hurricane. Second, the application of multiple hydrodynamic models at varying spatial scales delivers superior information about damaging coastal hazards near a transportation asset. Third, there may be similar opportunities to improve the resilience of low-elevation bridge spans to similar types of damage in future storm events. For low-elevation bridge spans over land, extending the embankment to higher elevations, or using something similar to the vegetated berms considered here, could potentially reduce their vulnerability to extreme events now and in the future.
Format:
PDF
Collection(s):
Federal Highway Administration
Main Document Checksum:
[+]
urn:sha256:224133e6c8120461da9ae546c0f38ec48095a374b68632e1e5f1b1c515e992c1
Download URL:
https://rosap.ntl.bts.gov/view/dot/58165/dot_58165_DS1.pdf
File Type:

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