What is HVRA?

What is HVRA?

Hazard, vulnerability and risk assessment (HVRA) is the combined process of quantifying the spatio-temporal return probabilities of various hazards, the expected degree of damage that a given element or set of elements-at-risk is exposed to and the expected monetary losses when a given area is exposed to hazards within a given period of time. This forms the most fundamental and primary activity in the disaster risk reduction cycle (Figure 1) and hence has to be a continuous process.
In the context of HVRA, the terms hazard, vulnerability and risk has specific definitions, they being:

  • Hazard (H): is the probability of occurrence of a potentially damaging phenomenon within a specified period of time, within a given area.
  • Vulnerability (V): the degree of loss to a given element or set of elements-at-risk resulting from the occurrence of a natural phenomenon of a given magnitude. Usually expressed on a scale from 0 (no damage) to 1 (total damage).
  • Elements at risk (E) means the population, properties, economic activities, including public services, etc. at risk in a given area.
  • Risk (R): the actual exposure of something of human value to a hazard, often expressed in monetary-value/time.

The universally accepted method for conducting HVRA follows the guiding formula:

R = H * V * Amount

Figure 2

where, Amount is the monetary-value of the element(s)-at-risk. Thus for each hazard probability scenario one can estimate a specific vulnerability and a specific risk. All this is easily said than done. There are complexities involved in all stages of this calculation, starting from hazard quantification (for example, how to calculate the return probability of epidemics, road accidents, lightning strikes etc.) to assigning a specific monetary-value to social elements at risk (for example, an ancestral temple, a tomb, a pregnant woman, etc.). All the three components of HVRA have spatial and temporal dimensions and the results if to be useful for administrators have to be spatially explicit and thus have to be maps generated in a Geographic Information Systems (GIS) environment that provides integrated spatial analysis capabilities. An example of vulnerability quantification is given in Figure 2. The urban area in the figure is expected to be affected by MMI 8 earthquake shock waves and the return probability of this earthquake was assumed to be 1 in 100 (0.01). The vulnerability was scaled as minimal damage (0.1), partial damage (0.5) and major damage (1). The monetary-value (Amount) estimation was not carried out in this case and thus the map technically represents spatial vulnerability of the buildings when exposed to an MMI 8 earthquake.