By Michael Brenneis
The Vermont Agency of Transportation, along with a list of partners (p. iv), has developed a planning tool to identify and prioritize parts of the transportation network most at risk of flooding, fluvial erosion, landslides, or other natural disasters. The need for a forward-looking approach to avoid or protect against roadway destruction, and keep people connected to needed resources, was illustrated in 2011 by the effects of Tropical Storm Irene. The Transportation Resilience Planning Tool (TRPT) was exhibited in a presentation at the 2019 SSTI State DOT Community of Practice meeting in Denver by VTrans Policy, Planning, and Research Bureau Director Joe Segale.
The interactive TRPT is designed to be used by municipal governments, planning commissions, conservation commissions, emergency management, or the public to “identify and prioritize vulnerable locations and to create a list of potential solutions.” The tool currently includes data for the Headwaters White River, Whetstone Brook, and North Branch Deerfield River watersheds in Vermont. Coverage of seven additional watersheds is anticipated by summer 2020, in time to inform the project budgeting process, according to Segale.
As stated on the TRPT web page, “The TRPT’s purpose is to identify vulnerabilities in a proactive manner to avoid or mitigate against the impacts of future damages in the most critical, highest risk locations.” The tool can be used to screen road segments, bridges, and culverts that are in the most critical locations, and facilitate the identification and prioritization of projects that will allow the hardening, protection, or controlled retreat from critical, vulnerable assets. Mitigation strategies include river and road stabilization, increased capacity for the conveyance of flood flows, floodplain protection, the relocation of roads at high risk, or the improvement of vegetation in critical areas.
The tool combines many spatial data layers including roads, bridges, culverts, elevation, river corridors, floodplains, the locations of previous storm damage, and the distance to emergency services. Using this data the tool returns a risk assessment score for a given asset, calculated as the average of its vulnerability and criticality.
Several data sets were either crucial to the success of the project, or time-consuming to collect. Vermont’s culvert inventory—culverts are often the most vulnerable roadway structures—took five years to complete, but resulted in a new regular schedule of inspection. The inclusion of the proximity to emergency services, river corridor delineation (p. A-7), and an enhanced definition of network criticality (p. 17), adds a robustness to this analysis. A user guide is available with detailed information about the data and methods needed to develop watersheds for inclusion in the tool.
Michael Brenneis is an Associate Researcher at SSTI.