Recent
hurricanes and other extreme events have resulted in substantial damage to North
Carolina’s transportation infrastructure. In some cases, the same locations
have been damaged multiple times, but the amount of damage differs, which
suggests that DOT strategies were effective. However, without a detailed
quantification of the performance differences, NCDOT engineers had had to rely
on qualitative and anecdotal evidence as to the effectiveness of various
strategies.
The research described in this report was conducted to fill this
gap by evaluating sites damaged and repaired following Hurricanes Matthew and
Florence. A series of detailed case studies were carried out to identify the
design factors and repair/maintenance decisions that led to better performance
during Hurricane Florence.
Resilience of Transportation Systems
Source:
Adapted from Linkov, I. and J.M. Palma-Oliviera (eds) (2017) Risk and
Resilience, Amsterdam: Springer.
The main conclusion from this effort is that that the actions taken by the NCDOT hydraulics unit and maintenance operations group following the recent hurricanes have been effective at increasing the robustness and reparability (i.e., resilience) of roadways with pipe crossings. It was also found that when pipes and culverts were redesigned following the hurricane related damage that they were almost always upsized, suggesting an historical bias in pipe sizing. It was also found that headwalls, extended rip rap along the banks or embankments, use of No. 57 stone as backfill or bedding, ensuring sufficient cover and managing headwater to bed-to-crown ratios when making design decisions, using (where possible) non-erodible or less-erodible soils, and mitigating side ditch slope issues had a positive effect on the overall robustness or reparability of culverts.
This research resulted in three primary recommendations. First, the NCDOT should continue to follow the practices used following Hurricanes Matthew and Florence. Second, the Survey 123 database should be enhanced to store additional information about the design and repair process. Third, the NCDOT should continue to monitor the performance and monitor flow rates at select sites cataloged in this research project.
