Qualitative Risk Assessment Institute for Water Resources 2009 Qualitative Risk Assessment Charles Yoe, PhD cyoe1@verizon.net

The Need Manage risk intentionally Do better than has been done Qualitative risk assessment can be a viable option Partial assessments sometimes helpful (not all steps)

Use Qualitative Assessment When consistency and transparency in handling risk are desired When theory, data, time or expertise are limited When dealing with broadly defined problems where quantitative risk assessment is impractical E.g., national levee safety ranking

Qualitative Risk Assessment The process of compiling, combining and presenting evidence to support a statement about risk Descriptive or categorical treatment of information Is formal, organized, reproducible method based on science, sound evidence and four steps Flexible and consistent Easy to explain to others Supports risk management decision making

Qualitative Methods Toolbox Increase or Decrease Risk Risk Narratives Evidence Mapping Screening Ratings Rankings Enhanced Criteria Ranking Operational Risk Management (Risk Matrix) Develop a Generic Process Qualitative Assessment Models Multi-Criteria Decision Analysis

Qualitative Assessment May include all or just some of the risk assessment steps Qualitative risk characterization is usually the endpoint Not every qualitative assessment is a true risk assessment

For Any Method Necessary preparation! Use an assessment framework Identify the problem Identify the goals Identify the questions to be answered Use an assessment framework

Increase or Decrease Risk For some problems it may be enough to know if things are getting better or worse Identify the direction of change in a risk and the specific reasons for it Storm damage has weakened structure Funding uncertainty clouds future Clarifies thinking and rationale Not good for netting changes

Risk Narratives What can go wrong? How can it happen? How likely is it? What are the consequences? Use simple narratives that answer these questions honestly Tell story of existing risk Tell story of mitigation effectiveness (risk reduction) Tell story of residual, transferred or transformed risk

Evidence Frameworks A risk evaluation technique Identify how experts evaluate current scientific evidence on chosen topics What conclusions do they reach regarding risk potential What evidence/arguments do they use to justify conclusions What consensus/disagreement exists What uncertainties remain Source: Risk evaluation of the health effects of mobile phone communication (10/2005) by Peter Wiedermann, Holger Schütz, and Albena Spangenberg

Core Elements Evidence base or data Pro and con arguments Includes supporting or attenuating arguments Conclusions of claim about existence of a hazard with remaining uncertainties

Ordering Techniques Screening, rating and ranking with increasing levels of detail/information Used to identify hazards, commodities, commodity-pathogen pairs, pathways, mitigation measures, potential risk and the like that are of interest to decision makers

Screening Process of separating elements into categories of interest and no interest through systematic elimination Requires Items to be screened Carefully defined categories (yes/no) Criteria for screening Evidence for the criteria An algorithm for using the criteria to separate the items into the desired categories

Screening Algorithms Domination procedures (better/worse on all criteria) Conjunctive procedures (meets all criteria thresholds) Disjunctive procedures (meets a least one criterion threshold) Elimination by aspects (set cut-off value for most important criterion and eliminate, then set cut-off value for next most important criterion, etc.) Lexicographic rules (rank against all criteria then rank alternatives)

Rating Systematic process of separating elements into multiple categories of varying degrees of interest Individuals are rated High, medium, low, no risk Requires Items to be rated Carefully defined categories (non-ordinal is okay) Criteria for rating Evidence for the categories An algorithm for using the criteria to separate the items into the desired categories

Ranking Systematic process used to put items in an ordinal sequence Rated items can be ranked May rely on ordinal ranked categories or an ordinal ranking of each individual item Simple when objective measures  of a risk or other characteristic of interest are available Requires Items to be ranked (alternatives) Carefully defined science-based criteria for ranking Evidence of each item’s measurement or rating for each criterion Differential weights for criteria when appropriate A synthesis algorithm.

Enhanced Criteria Based Ranking Ratings All Possible Combinations of Ratings Ranking Evaluate Reasonableness of Ranking Add Criteria New Combinations of Ratings New Ranking

Question? Which lock gates in division present the greatest potential risk to health and safety and therefore should be repaired first?

Step One: Criteria Assume criteria equally important (or not). Reflect most important aspects of evaluating risk. Define H, M, L scenarios for each criterion. Use three or four evidence-based criteria.

Step Two: Rating Use expert judgment to critically evaluate the available information Develop estimates for each “hazard” against criteria Use letters or numbers but numbers do not represent an absolute measurement of risk only a relative means for comparison

Step Three: All Possible Combinations Greatest Risk HHH HHM, HMH, MHH HHL, HLH, LHH, HMM, MMH, MHM HLM, MHL, HML, LMH, MLH, MMM, LHM HLL, LHL, LLH, MML, LMM, MLM MLL, LML, LLM Least Risk LLL This is for equally weighted criteria. Unequal weights yield different listings.

Step Four: Rank Subjectively Establish rank according to descending relative risk Identify subjective clusters.

Step Five: Add Criteria? Look at rankings, do they make sense? Have you thought properly about this issue? If they do not, perhaps you did not consider all the most relevant criteria A new criteria may be added to more accurately reflect the assessors rationale for ranking

Step Five: Add Criteria? (cont) Suppose the following was added to our example Criterion 4: Cost of emergency repair H = Major disruptions to navigation or power, much higher costs to repair M = Much higher costs to repair L = Same as scheduled repair

Step Six: New Ratings

Step Seven: New Ranking

You are working a on a beneficial uses of dredged materials study that is using good quality navigation maintenance dredging material to create wetlands in a wildlife refuge. Over the last several decades 7000 acres of coastal wetlands have been lost. You have limited budgets and no money for engineering studies. The risk of greatest concern is that the wetlands will not be established. Your task is to decide where you will place the material to establish wetlands. You will use hay bales to establish a containment structure adjacent to the shoreline, then you will pump materials behind the bales, the emergent land will then be planted. You will be ranking 20 different sites and you want to identify those sites with the greatest risk of failure or, alternatively, with the greatest chance of success. Using the methodology of the enhanced criteria hazard ranking method develop three criteria that will help you to identify the most hazardous locations for these wetlands. Then define a high, medium and low scenario for each of these criteria

Operational Risk Management (ORM)

Steps Determine purpose and use of matrix Identify the question to be answered Define consequences of interest Identify consequence ranges and definitions Identify likelihood ranges and definitions Identify levels of risk in the cells of the matrix

Your DE Has Seen This “Mishap Risk” DOD "Standard Practice For System Safety” MIL-STD-882D 10 February 2000

Consequence Severities

Probability Levels

Risk Assessment Values Each risk you assess is placed in a cell and managed accordingly

Risk Levels

Another Example Source: Assessing Environmental Risk, A Lecture to the Irish Environmental Law Association By: L. M. Ó Cléirigh 29 June 2004

Risk Matrix

Three Axioms Weak consistency Betweenness Consistent coloring 3x3 and 4x4 should look like this to minimize problems Source: What’s wrong with risk Matrices? By Louis Anthony Cox, Risk Analysis Vol. 28 No.2, 2008

The Risk Management Point of Matrix

Recently, Congress passed the National Levee Safety Act, which for the first time directed the Corps to inventory all private levees. In this case we have a programmatic level risk assessment and management problem and we will never have detailed data and analysis for a full blown risk assessment at every location. Given that the levee assessment program is in its infancy, and given the reality of limited data over time, use the ORM approach to devise probability and consequence categories that could be used for an initial qualitative risk assessment of these levees once they are identified.

Generic Process Probability of Adverse Impact Consequence of Risk = X Age x Condition x Usage x Event Economic Environmental Perceived Damage Damage Damage Potential Potential + +

Qualitative Assessment Models Probability hazard exists-rank as H,M,L Probability adverse consequence occurs if exposed-rank as H,M,L Probability exposure occurs-rank as H,M,L Overall risk estimate, integrate hazard, consequence, exposure- rank as H,M,L

MCDM/MCDA Multi-Criteria Decision Making (MCDM) is the study of methods and procedures by which concerns about multiple conflicting criteria can be formally incorporated into the management planning process Decision maker contemplates choice of action in an uncertain environment MCDA helps people choose among a set of pre-specified alternatives Decision making relies on information about these alternatives Quality of information can be scientifically-derived hard data to subjective interpretations Outcomes of decisions may be certain (deterministic information) or uncertain represented by probabilities and fuzzy numbers MCDA can assist in information processing and may lead to better decisions

Take Away Points Not all risk assessment needs to be quantitative Develop a few consistent techniques for your usage

Questions? Charles Yoe, Ph.D. cyoe1@verizon.net