Urban centres and flood risk

A recent BBC article (Shanghai ‘most vulnerable to flood risk’) reports on a paper published in Natural Hazards by a team of researchers. The paper ‘A flood vulnerability index for coastal cities and its use in assessing climate change impacts’ in the journal Natural Hazards by Balcia, Wright and van der Meulen, follows in a tradition of trying to quantify risk using a set of key variables. (I think the paper is on open access so you should be able to read it via the link). The authors develop what they call the Coastal City Flood Vulnerability Index (CCFVI) that is composed of three parts: the hydro-geologic, the socio-economic and the politico-administrative. These parts represent the three key interacting subsystems that affect coastal flooding, the natural subsystem, the social-economic subsystem and the administrative and institutional subsystem. Within each of these the authors identify variables that indicate the degree of exposure to hazard, the susceptibility to the hazard and the resilience to the hazard. The hydro-geologic part only has indicators of exposure whilst the ‘human’ parts have indicators of all three.

Exposure is defined as the predisposing of a system to be disrupted by a flood event due to its location. Susceptibility is defined as the elements exposed within the system that influence the probability of being damaged during the flood event. Resilience is defined as the ability of a system, community or society to adapt to a hazard. This term is assessed through political, administrative, environmental and social organisational evaluation. Variables selected include sea-level rise, storm surge, number of cyclones in last five years, river discharge, foreshore slope, soil subsidence for the hydrogeologic subsystem. For the socio-economic subsystem the population close to the shoreline, the growing coastal population as well as cultural heritage are included as exposure factors whilst uncontrolled planning zones are an exposure variable for the political and administrative subsystem.  Susceptibility variables include the percentage of the population disabled or young or old and flood hazard maps. Resilience variables include shelters, level of awareness, institutional organisations and flood protection.

The paper carries out a detailed analysis of each subsystem and then combines the indicators into a single equation to determine overall vulnerability.  The selection of variables is well argued and the complexity and issues of using such indexes is discussed well, so the authors do not have a simplistic interpretation of hazards and vulnerability. Any paper that tries to squeeze and freeze the complex and dynamic concept of risk into a single index will always have the problem of simplification. Simplification, not only of the subsystems but also of the interpretation by others of the index itself.

The variables selected may reflect the data readily available plus a particular view of how the flood hazard should be alleviated. The focus on institutional organisations as resilience does imply a rather hierarchical view of hazard management and prevention (maybe a valid argument with a set of large urban areas with low social cohesion). Interpretation of the index, as in the BBC report, tends to focus on the final product rather than on the variables used in its construction and the ratings of the subsystems. Discussions could be made as to the appropriateness of the same variables for cities across the globe or for the selection of those variables anyway. Looking in detail at the breakdown of the index, it is clear that Shanghai is the most ‘vulnerable’ city on variables used to determine the hydro-geologic subsystem because of its high length of coastline and high river discharge (plus high soil subsidence). Manila, however, is ranked second because of its exposure to tropical cyclones and flooding – can both the same index combine both types of exposure? Does this mean that Manila is a more vulnerable location, as tropical cyclones are more frequent than high discharges? Can degrees of difference in vulnerability or rather exposure be assessed using a combined index? Shanghai is not, however, the top ranked city for all subsystems. For the economic variables, Shanghai is ranked fourth meaning that it is likely to recover quickly, economically at least, from the affects of a flood event.

An index like the one presented in this paper are very, very useful. They can be used, as the authors have done, to try to predict how changes in climate could impact on hazards and as such can be of great use in planning and management. A single index should, however, be used with caution, particularly if the choice of variables reflects a particular view of hazard management. Similarly, understanding how the index is constructed and how different parts of the index contribute to the whole is vital in understanding where vulnerability (and resilience) lie and how these might be improved.

Public Risk Communication

Communicating risk to the general public is a vital task in managing risk. The UK government has produced a leaflet outlining a ‘Practical Guide to Public Risk Communication’. The leaflet is a very short guide to practice. The three key aspects of risk communication are to reduce anxiety around risks, to manage risk awareness and to raise awareness of certain risks. There are 5 key elements to public risk communication: assembling the evidence, acknowledgement of public perspectives, analysis of options, authority in charge and interacting with your audience.


Each of these elements is expanded and discussed via a set of questions that organisations should consider. The first element is concerned with establishing the nature of the risk and its magnitude and demonstrating a credible basis for the position taken by the orgnaization. Evidence is paramount in this element but also, implicitly, is the question of trust or belief in the evidence. Who provides the evidence and the basis of that evidence are as important as clearly articulating the risk. As part of this aspect of trust, the question of ambiguity and uncertainty is bound to arise. Despite what politicians may wish, science is inexact and often searches for and is ladened with uncertainty. How organisations deal honestly with uncertainty can have a huge bearing on the trust they emit and retain between hazardous events.

Understanding how the public understand risk is essential to getting the message across. Lumping everyone in as ‘the public’, may not be that helpful though, as the leaflet notes. Assuming everyone perceives a hazard in the same way and in a consistent manner may be hoping for too much. The leaflet uses the term ‘risk actors’ as a coverall term for individuals or groups who engage with a risk or who influence others approaches to and understanding of risk. Perception and so the message about risk should be differentiated but that differentiation may depend upon the exact mix of risk and risk actors. An issue I would like to raise here is whether once you are a risk actor you are no longer a member of the public? A home-owner who has recently experienced a flood may be much more active in their local community in taking steps to reduce the flood risk – does that make them a risk actor, a well-informed member of the public or a member of the public and does this matter fro how risk is communicated to them? Risk actors could be viewed as being bias, of having their own agendas, and so not really reflective of the views of the general public.

Analysing options suggests that organisations have rationally weighed the risk and benefits of managing public risk as well as the options for action available to them. The last sentence is interesting ‘the technical and societal interests will need to be reconciled if the solution is to be generally accepted.’ This sentence is made in relation to technical solutions that may no have public sympathy initially. The implication that through debate these solutions can be accepted implies a very hierarchical and technocratic view of hazards and risk management – the public have to be educated and brought to accept the solution. I maybe reading this aspect too cynically but may be not.

The authority in charge section, however, adds weight to the idea that this is a technocratic and hierarchical view of hazards (maybe not a surprise in a government publication!) The need for an organisation to determine if it is appropriate for them to step into manage risk and the clear limits of responsibility to risk management imply a very structured and ordered view to how to manage the world and associated risks. A telling point is made that exercising authority now is as much about building and maintaining trust as it is about lines of formal authority. Trust, or rather the perception of trust, will dramatically affect the ability of an organisation to manage risk in a sceptical society. The last sentence states ‘Organisations that are not highly trusted will increase the chances of success by enlisting the help of other organisations – such as independent scientific organisations – who have the confidence of society’. A call to collaboration or a call to objectivity?

So is it all ‘smoke and mirrors’ or does this leaflet help to further risk management? Without a doubt communicating risk and its management effectively to different audiences is essential. The leaflet does provide some very good guidance on this. The ideas should not, however, be used uncritically as they are designed with a very technocratic and hierarchical view of risk management in mind. Examples of public risk communication are also provided and for flooding the conclusions reflect this bias (starts on page 22 of the report). Risk quantification is sought for flood hazard, as are software and tools for aiding local risk planning and managing the possible clash between the expectations of more flood defence infrastructure and the new risk-based approach (risk is the focus rather than the hazard itself). Communication about risk and its management is viewed as coming from the Environment Agency , insurance companies and DEFRA – not much about local ideas or communication from the ground up! The link itself is, however, viewed as potentially corrosive to public trust. This hits at the nub of the issue, the government wants the trust of people to be able to act in a manner it views as appropriate. Actions, of necessity in a complex society, require working with organizations with their own agendas and this creates suspicion. Can risk ever be managed without trust and can you manage anything without eroding some degree of trust somewhere?