Whether floods and droughts are caused by global warming or are down to more familiar natural cycles, they already take a massive human and financial toll. Floods alone have affected 2.3 billion people and caused more than USD660 billion in damage in the decade to 2015.1 Policymakers struggle to respond.
Typically, solutions to these problems have tended to involve massive and expensive civil engineering projects, but often that’s just treating the side-effects of something that’s much more fundamental, explains Dr David Lloyd Owen, managing director of Envisager, a water consultancy.
Floods have affected 2.3 billion people and caused more than USD660 billion in damage in the decade to 2015.
There are better ways of dealing with floods and droughts, he says.
“Rather than pouring yet more millions of cubic meters of concrete to solve the problem, the bodies responsible for water and sewage systems — be they public authorities or private utilities — will have to think more broadly about how to manage water resources and deal with disasters.
“This will entail much more integrated approaches that could end up encompassing a region’s whole watershed. Alternatively, the answer might mean stepping back to let nature take its course and then only responding with appropriate emergency measures.”
In all cases, however, dealing with floods and droughts means generating and gathering better data, and doing so more efficiently.
This could include improved mapping of flood plains, accurately measuring soil’s ability to retain moisture, or doing appropriate cost-benefit analysis for flood prevention against post-emergency responses.
A big problem
It’s not clear to which degree floods and droughts are being triggered by climate change. In part, that’s because climate science focuses on shifts in averages — whether temperature or rainfall — whereas floods are extreme events, and there’s little clear evidence extreme events are becoming more common.
A 300-year survey of Nile data shows that it’s impossible to determine what counts as “normal” in terms of the river’s flood patterns.
What’s more, if climate change creates losers from floods and droughts, it can also create winners — climate change will, for instance, improve agricultural conditions on some previously infertile land.
But that’s not to minimise the costs of flooding. The UK alone suffers GBP1.4 billion (USD1.7 billion) in annual flooding costs.2 In the European Union, flooding costs amounted to EUR4.9 billion (USD5.2 billion) in each of the first 12 years of this millennium. That could rise to EUR23.5 billion (USD24.9 billion) a year by 2050 if extreme flooding events start to happen every decade on average, rather than every 16 years as is the case now.3 Other estimates suggest some 18 per cent of the EU’s 170 million households are at risk of flooding.4
Globally, the average annual costs of flooding is estimated to be USD10.8 – 19.8 billion. Using base assumptions of an eight to one benefit to cost ratio, this implies that flooding alone could require annual spending of up to USD2.5 billion to avert these losses.
The United Nations Office for Disaster Risk Reduction, meanwhile, estimates that USD42 billion needs to be spent on flood protection worldwide.
If too much rain causes sudden cataclysms, too little can lead to slower, but longer-lasting disaster. Unlike floods, which come on suddenly and have an immediate impact, droughts come with social and economic costs that build over much longer timescales. In some cases they can be part of multi-year cycles.
Partial droughts, while largely an irrelevance for much of the economy, can have several adverse side-effects that are not immediately obvious.
For instance, while a European drought in 2003 mostly caused just general inconvenience, reduced river flow in France meant that that electricity generation at 17 of the country’s 58 nuclear reactors had to be dialled down or completely shut until conditions returned to normal.6
Spending in context
In a nutshell, the impact of both floods and drought can be massive. Yet any planning to mitigates these natural disasters needs to be considered in context. A great deal can be misspent on flood protection against relatively rare or benign events. For example, Singapore has poured considerable resources into controlling flash floods that last, on average, just 26 minutes and, at most, tend only cause the minor inconvenience of a few traffic jams.
Nor is it clear that London’s GBP4.2 billion (USD5 billion) ‘super sewer’ infrastructure project, a 25 kilometre tunnel running under the river Thames, is the most efficient answer to the overflow of sewage into the river when storm drains occasionally overfill. Policymakers’ tendency to build white elephants shouldn’t be underestimated.
In some cases, targeted and efficient emergency response is the best approach to dealing with flood disaster, rather than spending vast sums on prevention.
In some cases, targeted and efficient emergency response is the best approach to dealing with flood disaster, rather than spending vast sums on prevention. In others, it’s a matter of improving maps of flood plains to better control building on risk-prone sites, or of ensuring that electricity supply is maintained to sewerage-treatment plants during floods.
“Floods and droughts need to be managed differently in monsoon countries like India, where 80 per cent of the annual rainfall occurs within 70-120 hours, but not consecutively. This is very different compared to the situation in many Western countries,” says Professor Asit K. Biswas, co-founder of the Third World Centre for Water Management.
“For example, even though average annual rainfall in Delhi is significantly higher than London, at 79 centimetres compared to 59 centimetres, Delhi is much drier.
“This is because rainfall in London over the entire year is relatively uniform but in Delhi it is concentrated primarily during the three months of July to September. Thus, the highest soil moisture ever recorded in Delhi is lower than the lowest in London, even though annual rainfall is significantly higher in Delhi than London.”
That helps to explain why one of the world’s rainiest places, Cherrapunji, India, which has annual average rainfall of almost 20 times that of London, has been having serious water problems for over the past decade during the dry months of November to April.
“India’s water management must focus on how to capture and store the immense amount of rain that falls during the few monsoon months so that water is made available for all uses and users throughout the year and in between the years,” Prof. Biswas explains, adding that it would also significantly reduce the adverse impacts of floods and droughts.
Whatever the solution, technology clearly has a key part to play.
Modelling flooding patterns and weather systems, measuring soil saturation and loading of sewerage networks are just some examples of how big data and other technological developments can play a role in flood prevention.
Flood management software is also being deployed to model the risks of building on given sites.
Meanwhile, governments are implementing more flexible flood defences. In the UK, for instance, traditional sea and river walls are, in places, being removed to allow open wetlands to absorb seasonal variations in water levels.
These are activities that will only grow in importance as governments take more sophisticated approaches to disaster prevention and mitigation.
As for droughts, water resource management becomes particularly pressing. In some cases, this can be a matter of creating sufficient storage capacity in the form of reservoirs. In others, the issue is one of better infrastructure maintenance.
One approach is investment in recycling wastewater. Companies like Xylem are developing innovative filtration and ultraviolet systems that kill and remove biological and chemical pollutants.
Elsewhere, desalination plants are an option where energy is cheap and there is ready access to seawater. There are other innovations that capture fresh water from fog.
But one of the main solutions boils down to plugging leaks.
Studies by Professor Biswas show that most urban centres of the Indian subcontinent, Middle East and Latin America now routinely lose 40-60 per cent from their water supply systems due to leakages and unauthorised connections. Yet, system losses in Tokyo are 3.7 per cent, Singapore 5 per cent, and Phnom Penh 6.5 per cent, “a small fraction of much of the developing world,” he notes.
Who pays?
Floods and droughts are big and undoubtedly complex problems confronting policymakers. Issues that have to be faced, because persevering with traditional approaches is no longer environmentally or socially tenable.
But careful analysis is crucial to ensure that measures are proportionate and cost-effective. Sometimes it boils down to better maintenance of the wider physical environment.
1 The Human Cost of Weather Related Disasters 1995-2015, UNISDR Centre for Research on the Epidemiology of Disasters (CRED)
2 Department for Environment, Food and Rural Affairs estimates.
3 “Increasing stress on disaster risk finance due to large floods,” Jongman B., Hochrainer-Stigler S. et al, Nature Climate Change 4, 264-268 (2014)
4 “Flood risk in Europe: analysis of exposure in 13 countries,” Lugeri N. et al, Institute for Environment and Sustainability (2006)
5 United Nations and World Bank estimates respectively.
6 http://www.nytimes.com/2007/05/20/health/20iht-nuke.1.5788480.html
