Quantifying road vulnerability to coastal hazards: Development of a synthetic index

As part of a collaborative study with the Ministry of Transport of Quebec, a Coastal Road Erosion and Flooding Vulnerability Index (CREFVI) was developed for the short (2020), medium (2060) and long term (2100). Nine study sites in Eastern Quebec (Canada) were used to develop the index, for a total of 122.4 km of roads. The index includes 14 parameters relating to the following: the exposure of a site to erosion and coastal flooding hazard; the characteristics of the road segment; the characteristic of the road network; and adaptation to erosion (e.g. the presence of defence structures). Each parameter received a score between 1 and 5 according to its propensity to increase (5) or not (1) the vulnerability of the road. CREFVI values for the study sites vary between 0 and 159.1 and have been divided into 5 classes reflecting the actions needed to reduce the site's vulnerability: Not vulnerable (no intervention necessary), Low, Medium, High, Critical (immediate intervention required). For the roads analyzed, 0.5 km have a critical CREFVI value as of 2020, 1.7 km as of 2060 and 2.6 km by 2100. Currently, only 20.6% of the road segments are vulnerable to coastal hazards, but this percentage rises to 36.4% by 2060 and to 54.3% by 2100. This index is an important decision-making tool for improving road management, prioritizing future actions and determining which parameters require intervention.