Developing an Extreme Weather Event Risk Framework: Houston Case Study

Jolanda Prozzi, Texas A&M Transportation Institute
Andrew Birt, Charles Gurganus, Andrew Wimsatt (Texas A&M Transportation Institute)
Topic Area
Sustainability and Resilience in Transportation Systems

The Federal Highway Administration (FHWA) selected the Texas Department of Transportation (TxDOT) to pilot the development of an extreme weather event risk framework using the TxDOT Houston District as a case study. The purpose of the developed risk assessment framework was to understand extreme weather event threats - specifically, inland flooding - and the potential impact on the transportation network, as well as provide a data-driven approach to identify mitigation strategies and prioritize investment decisions.

TxDOT contracted with the Texas A&M Transportation Institute (TTI) to develop the extreme weather event risk framework. The study team performed the following tasks:
- Conducted a literature review to identify the climate factors of concern to TxDOT's Houston District.
- Conducted a workshop to focus the pilot effort on the climate factor of most concern to stakeholders. Based on the input received, the study team focused on characterizing inland flooding and its impact on Houston's road infrastructure.
- Reviewed data resources and information potentially useful for characterizing flooding in Houston.
- Translated spatial information of 100- and 500-year flood zones into a spatial view of inundation characterized by flood height.
- Analyzed Light Detection and Ranging (LiDAR) data to provide information on the elevation of road infrastructure (pavements) in Houston.
- Calculated the potential impacts of flooding on Houston's pavement infrastructure and calculated the potential loss in service life.
- Calculated the potential systems impacts of flooding on Houston's road infrastructure in terms of infrastructure impacts (loss in pavement service life) and disruption impacts (road closures due to flooding).
- Identified potential mitigation measures and investment priorities to increase the resiliency of Texas's road system to flooding in Houston.
- Identified potential proxy indicators that the agency can track in the future.

The study team found that thinner pavement structures, particularly those without treated subgrades and less than two inches asphalt are particularly vulnerable to flooding. Strengthening unbound layers such as subgrades and base materials with stabilization techniques helps mitigate pavement damage caused by flooding. Thinner pavement structures, however, represent a very small percentage of the Houston's state maintained network (i.e., 53 miles). On the other hand, the findings of the pilot project highlighted the potential disruptive effects of flooding and the significant cost of elevating susceptible roads. The analysis revealed that almost 12 percent of the state-maintained lane-miles in Harris County are at risk of flooding in the case of 100-year events. Most of the impacts will lead to disruptions in travel rather than chronic damage to the pavement structure.

Abstract Keywords
Resiliency
extreme weather
asset management