The Hazards Vulnerability Similarity Index

The Resilient-C research team developed the Hazards Vulnerability Similarity Index (HVSI) as a means to quantitatively measure the similarity between two communities in terms of their hazard vulnerability profiles, defined using a set of 25 hazard vulnerability indicators.

Using the HVSI, a user can assess the degree of similarity in coastal hazards vulnerability between any two communities in the Resilient-C database. An overall similarity can be established using all 25 indicators, using the five indicators for a specific capital (e.g., social), or at the level of individual indicators (e.g., total population and coastal land use).

The HVSI was first described in a 2015 paper entitled, Using vulnerability indicators to develop resilience networks: a similarity approach. That paper defines the HVSI using the equation:

$$\bbox[1em]{HVSI(x,y) = \frac{\sum_{k=1}^n{w(x_k, y_k) s(x_k, y_k)}}{\sum_{k=1}^n{w(x_k, y_k)}}}$$

Equation: The Hazards Vulnerability Similarity Index equation (Chang et al., 2015)

where `x` and `y` describe two communities, respectively, and are described using `n` vulnerability indicators. The quantity `s(x_k, y_k)` measures the similarity between the `k`^th indicator of `x` and `y`, and `w(x_k, y_k)` is the weighting of the `k`^th attribute.

HVSI values can range from zero, indicating complete dissimilarity, to one, indicating the two communities share identical hazards vulnerability profiles. The strength of this method is its ability to handle the challenge of fragmented data availability, giving weights of zero when one or both communities do not have a value present for a given indicator, something that is very common in this type of study.

For more information on the HVSI and the Resilient-C platform, please refer to the research articles posted on this website.