Fragility and Urban Planning

The recent book Antifragility by Nassim Nicholas Taleb (2012) provides an interesting analysis of the concepts of ‘fragility, robustness and antifragility’. Antifragile entities tend to improve, even thrive under the stress of extreme events. Of interest in this blog entry, however, are some of the comments made concerning extreme events and the transfer of fragility and the implications of these for the ‘relaxation’ or ‘simplification' of planning (depending on your viewpoint) outlined in the ASC Report published last year and increasingly being acted upon.


Taleb’s comment about ‘the worst case scenario’ being based on what we already know is an important one. The tables on page 28 and 29 of the ASC report, as noted in a previous blog, provide estimates of the stock at risk based on modelling of flood risk that is based on extrapolating existing data. This provides information of the risk based on current information about extreme events. These events are known, but as Taleb points out that it is the events beyond these that will become the ‘new’ extreme events to be incorporated into the next set of predictive models. Planning for the worst-case scenario that we know of or can model (unless way into the extreme tails of the modelled distribution) is likely to mean that the next, new ‘extreme’ event will be of a higher magnitude than the last extreme event.

The locking-in of long-term investment into development in areas already protected by flood defences could be seen as increasing the fragility of development. As the magnitude ‘new’ extreme events emerges these will force the continued investment of funds into protecting the increasingly vulnerable developments behind these flood defences. The focusing of development in these supposedly protected areas increases the potential impact of these new extreme events, as there is increasingly more development capable of being destroyed. The ASC Report states that for every £1 spent on flood defences there is an expected reduction in long-term costs of flood damage of £8. Does this cost-benefit ratio hold once an extreme event breaches the defences? Does the concentration of such value behind a single defensive barrier mean that there is more value to lose in one single event even if the long-term average seems to be reasonable? Is the magnitude of the losses from a single event so great as to render discussions of averages irrelevant?
It could be argued that focusing development in these protected areas is a responsible approach to the uncertainty of future environmental change but the question needs to be asked for who is it a responsible approach? Who is at hazard from this development and who effectively transfers the potential fragility of the location? Simplifying the situation dramatically, it could be argue that builders and local authorities have a ready-made infrastructure to use in these areas and can quickly build new housing, so benefit from such concentration. They also have defences against flooding in place that they can point to as providing protection for these developments (and can improve over time as the cost-benefit aanalysis dictates). House buyers may have little choice but to buy where new housing is built. The moral hazard becomes theirs. Fragility is transferred from the builder and authorities to the individual, to the householder. The focus after any event is on the individual and their lack of insurance, their misunderstanding of the risk, their need to recover, the need for the community to rally together. The fragility inherent in the system is transferred to the home-owner is not even thought about as being a historically constructed thing that invovled the builders and the authorities. Is this a similar view to that taken by the banks after the banking crisis? Taleb makes the comment that Roman engineers were often made to sleep under the bridges they built so that they had some ‘skin in the game’ (another favourite Taleb phase). If the bridge failed the Roman engineers suffered for it, they had something to lose – is it an idea we should extend to development and all the actors in it?

Flooding and Development in the UK: Some thoughts on ASC Report

The recent ASC Report provides some interesting insights into current planning practices in the UK in relation to flooding. The ASC report (chapter 2) suggests that climate change is not the only factor increasing flood risk (page 27). It points out that risk changes if the probability of an event occurring changes OR if the consequences of an event alter. The first aspect is meant to cover the purely physical aspects of a hazard or rather of climate change in affecting flooding, whilst the second aspect is meant to relate to the socio-economic aspects of a hazard. It could be argued that a hazard isn’t really a hazard unless people are involved so an ‘event’ isn’t really a hazardous event unless there is a vulnerable population, so the two aspects may be more tricky to separate than appears. The two may go hand in hand.


Leaving this aside, the report does highlight the importance of the need for planning that bears these aspects in mind. The tables on pages 28 and 29 also provides some estimates of the amount of stock at risk from different types of flooding with 1.2 million properties at risk from river flooding, 230,000 of these at significant risk (a greater than 1 in 75 chance in any given year). The report points out that most floodplain development is within built-up areas that already have flood defences. Continuing development behind these existing defences increases the total value of assets that are being protected. In any cost-benefit analysis this increased value will make any future investment decisions easy – keep investing in defences as the value of assets keeps increasing. This means that current flood defences lock-in long-term investment, meaning that higher and stronger defences are continually required. The report recognises that this has been known for a while as the ‘escalator effect’.

The report also identifies that only a small number of planning applications have been approved when there was a sustained objection from the Environment Agency (EA). This implies that most planning applications meet the requirements of the EA for taking into account flood risk – a comforting point. However, the report also notes that, in general, local authorities are implementing national planning policy by continuing to build with protection in floodplains (page 36 of the report). In addition most flood risk management policies in plans focus on making development safe once the strategic decision to build in floodplains has been taken (page 37 of the report).

Combined this implies that floodplain development will continue and will produce an investment strategy for flood defences that encourages further development in already protected areas, forcing further and more extensive protection of these areas. The report states that the EA as taken a strategic approach to funding structural flood defences ‘targeting investment towards communities at greater flood risk and with the highest social vulnerability’ (page 40). The justification for this approach, however, is then expressed in terms of average cost-benefit ratio of 8:1, i.e. for every £1 spent on flood defences there is an expected reduction in long-term cost of flood damage of £8. This implies that social vulnerability is defined in terms of money as are any other benefits. This would suggest that assets that are relatively easy to attach a monetary value to will weigh heavily in these calculations. Again this would encourage development in flood protected areas as any additional value from the buildings an infrastructure will increase the cost-benefit ratio and so ensure the continuation of more, stronger and higher flood defences. Whilst here is nothing inherently wrong with this it does mean that if or when the defences are breached the cost of flood damage will be huge. How is this potentially high magnitude cost worked into the cost-benefit equations? Is the potential loss or cost discounted and over what time scale? How does the probability of such a high magnitude loss change as both aspects of flood risk mentioned above, the physical and the socio-economic, change into the future? Is the potential cost so huge that the defences must alwasy be enhanced into the future no matter what the rate of cliamte change or the cost? Is the current strategy commiting the future to locational inertia of housing, business and infrastructual investment?