Vulnerability Assessment

From SEA.unu.edu/wiki

(from van Straaten 1996)

Vulnerability analysis projects a planned activity onto the vulnerability of the original system. Vulnerability in this context is the combination of sensitivity and a valuation of the system. Vulnerability is also linked to a specific sub-activity and linked impact group (e.g. desiccation, eutrophication). Basically, vulnerability analysis works with maps, linking a continual or discrete vulnerability value to a cartographic object. In this way, different alternatives for e.g. groundwater extraction units can be evaluated by calculating a weighted total figure.

A typical vulnerability analysis follows the following steps:

1. Analysis of the proposed action into sub-activities and related impact groups: definition of the final impact-groups for which vulnerability maps are to be designed. For instance, for a motorway network, one might have the following impact groups

impact group:	affecting (target variable):
habitat destruction	flora and fauna
(temporal) desiccation	flora and fauna
barrier impact	fauna
disturbance (noise)	fauna
noise disturbance	people
barrier impact	people (local transport)
fragmentation	landscape, flora and fauna

One might also have the following 'help variables':

   * map of expected noise increase
   * map of location of drainage of run-off water
   * map of expected groundwater decline

2. Preparation of vulnerability maps for each 'target variable' based on:

   * existing baseline data;
   * (sub)activity-impact models, definition of geographical objects (vulnerability units);
   * vulnerability (= integration of sensitivity and valuation of environmental systems)

3. Projection/overlay of the vulnerability maps (target variables and help variables) with the sub-activity using GIS. For instance a map regarding the vulnerability of ecosystems to a groundwater decline (expressed in three vulnerability classes) can be overlaid on a map of areas where groundwater decline is expected (obtained by a rough hydrological analysis). This results in an area-figure for each vulnerability class.

4. Aggregation of impact-groups, possibly through weighted summation or multi-criteria analysis. In many cases, an assessment on this level of decision-making will also be supported by information of the proposed activity's impact on existing policies or legal restrictions (e.g. special protected areas, nature policy plans, water management plans, land-use plans).

Advantages:

• Allows quantitative expression (which is useful in comparing alternatives)
• 'Avoids' the problem of cumulative impacts: impacts are not predicted but assumed and the amount of impact is less important.
• Uses the geographical characteristics of the environment.
• Because vulnerability uses the local (geographical) characteristics of the environment, the approach is also useful on location-level EIA.

Disadvantages:

• Can be costly and time-intensive
• Only works with impacts that can be mapped.
• "Hides" its subjectivity: the concept of vulnerability involves value judgements, but these are "hidden" in the final analysis.

Further information:

van Straaten (1996)