Townsville floods show cities that don’t adapt to risks face disaster


Cecilia Bischeri, Griffith University

A flood-ravaged Townsville has captured public attention, highlighting the vulnerability of many of our cities to flooding. The extraordinary amount of rain is just one aspect of the disaster in Queensland’s third-biggest city. The flooding, increasing urban density, the management of the Ross River Dam, and the difficulties of dealing with byzantine insurance regulations have left the community with many questions about their future.

These questions won’t be resolved until we enhance the resilience of cities and communities against flooding. Adaptation needs to become an integral part of living with the extremes of the Australian environment. I discuss how to design and create resilient urban landscapes later in this article.




Read more:
Queensland’s floods are so huge the only way to track them is from space


Flood risk and insurance

Another issue that affects many households and businesses is the relationship between insurance claims and 1-in-100-year flood event overlay maps. Projected rises in flood risks under climate change have led to concerns that parts of Townsville and other cities will become “uninsurable” should the costs of cover become prohibitive for property owners.

Council flood data used for urban planning and land-use strategies is also used by insurers to assess the flood risk to individual properties. Insurers then price the risk accordingly.




Read more:
Lessons in resilience: what city planners can learn from Hobart’s floods


However, in extraordinary circumstances, when the flooded land is actually larger than the area marked by the flood overlay map, complications emerge. In fact, that part of the community living outside the map’s boundaries is considered flood-free. Thus, those pockets of the community may have chosen not to have flood insurance and not have emergency plans, which leaves them even worse off after floods. This is happening in Townsville.

Yet this is nothing new. Many people experienced very similar circumstances in 2011. Flood waters covered as much land as Germany and France combined. Several communities were left on their knees.

Notwithstanding the prompt and vast response of the federal government and Queensland’s state authorities, a few years later Townsville is going through something alarmingly similar.

Adaptation to create resilient cities

To find a solution, we need to rethink how to implement the Queensland Emergency Risk Management Framework. That is no easy task. However, it starts with shifting the perspective on what is considered a risk – in this case, a flooding event.

Floods, per se, are not a natural disaster. Floods are part of the natural context of Queensland as can be seen below, for instance, in the Channel Country.

Floods are part of the Australian landscape. Here trees mark the seasonal riverbeds in the Queensland outback between Cloncurry and Mount Isa.
Cecilia Bischeri, Author provided

The concept of adaptation as a built-in requirement of living in this environment then becomes pivotal. In designing and developing future-ready cities, we must aim to build resilient communities.

This is the ambitious project I am working on. It involves different figures and expertise with a shared vision and the support of government administrations that are willing to invest in a future beyond their elected term of office.

Ideas for Gold Coast Resilientscape

I live and work in the City of Gold Coast. Water is a fundamental part of the city’s character and beauty. In addition to the ocean, a complex system of waterways shapes a unique urban environment. However, this also exposes the city to a series of challenges, including flooding.

Last September, an updated flood overlay map was made available to the community. The map takes into account the projections of a 0.8 metre increase in the sea level and 10% increases in storm tide intensity and rainfall intensity.

These factors are reflected in the 1-in-100-year flood overlay. It shows undoubtedly that the boundaries between land and water are changeable.

Building walls between the city and water as the primary flood protection strategy is not a solution. A rigid border can actually intensify the catastrophe. New Orleans and the levee failures during the passage of Hurricane Katrina in 2005 provide a stark illustration of this.

Instead, what would happen and what would our cities look like if we designed green and public infrastructures that embody flooding as part of the natural context of our cities and territory?




Read more:
Design for flooding: how cities can make room for water


The current project, titled RESILIENTSCAPE: A Landscape for Gold Coast Urban Resilience, considers the role of architecture in enhancing the resilience of cities and communities against flooding. The proposal, in a nutshell, explores the possibilities that urban landscape design and implementation provide for resilience.

RESILIENTSCAPE focuses on the Nerang River catchment and the Gold Coast Regional Botanic Gardens, in the suburb of Benowa. The river and gardens were adopted as a case study for a broader strategy that aims to promote architectural solutions for a resilient City of Gold Coast. The project investigates the possibility of using existing green pockets along the Nerang River to store and retain excess water during floods.

Gold Coast Regional Botanic Gardens is one of the green areas along the Nerang River that could be used to store and retain flood water.
Batsv/Wikimedia Commons, CC BY-SA

These green spaces, however, will not just serve as “water tanks”. If mindfully planned, the green spaces can double up as public parks and facilities. This would enrich the community’s social realm and maximise their use and return on investment.

The design of a landscape responsive to flooding can, by improving local urban resilience, dramatically change the impact of these events.

The goal of creating urban areas that are adaptive to an impermanent water landscape is the main driver of the project. New Orleans after Hurricane Katrina and New York after Sandy are investing heavily in this direction and promoting international design competitions and community participation to mould a more resilient future. Queensland, what are we waiting for?




Read more:
Floods don’t occur randomly, so why do we still plan as if they do?



This article has been updated to clarify the use of flood data by insurers in assessing risk and the cost of cover.The Conversation

Cecilia Bischeri, Lecturer in Architecture, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Globally, floods seem to be decreasing even as extreme rainfall rises. Why?


Seth Westra, University of Adelaide and Hong Xuan Do, University of Adelaide

Over the past decade we have seen a substantial increase in our scientific understanding of how climate change affects extreme rainfall events. Not only do our climate models suggest that heavy rainfall events will intensify as the atmosphere warms, but we have also seen these projections start to become reality, with observed increases in rainfall intensity in two-thirds of the places covered by our global database.

Given this, we might expect that the risk of floods should be increasing globally as well. When it comes to global flood damage, the economic losses increased from roughly US$7 billion per year in the 1980s to US$24 billion per year in 2001-11 (adjusted for inflation).

It would be natural to conclude that at least some of this should be attributable to climate change. However, we know that our global population is increasing rapidly and that more people now live in flood-prone areas, particularly in developing countries. Our assets are also becoming more valuable – one only needs to look at rising Australian house prices to see that the values of homes at risk of flooding would be much greater now than they used to be in decades past.

So how much of this change in flood risk is really attributable to the observed changes in extreme rainfall? This is where the story gets much more complicated, with our new research showing that this question is still a long way from being answered.

Are floods on the rise?

To understand whether flood risk is changing – even after accounting for changes in population or asset value – we looked at measurements of the highest water flows at a given location for each year of record.

This sort of data is easy to collect, and as such we have reasonably reliable records to study. There are more than 9,000 streamflow gauges around the world, some of which have been collecting data for more than a century. We can thus determine when and how often each location has experienced particularly high volumes of water flow (called “large streamflow events”), and work out whether its flood frequency has changed.

A streamflow gauging station in Scotland.
Jim Barton/Wikimedia Commons, CC BY-SA

We found that many more locations have experienced a decrease in large streamflow events than have experienced an increase. These decreases are particularly evident in tropical, arid, and humid snowy climate regions, whereas locations with increasing trends were more prevalent in temperate regions.

To understand our findings, we must first look closely at the factors that could alter the frequency and magnitude of these large streamflow events. These factors are many and varied, and not all of them are related directly to climate. For example, land-use changes, regulated water releases (through dam operations), and the construction of channels or flood levées could all influence streamflow measurements.

We looked into this further by focusing on water catchments that do not have large upstream dams, and have not experienced large changes in forest cover that would alter water runoff patterns. Interestingly, this barely changed our results – we still found more locations with decreasing trends than increasing trends.

The Australian Bureau of Meteorology and similar agencies worldwide have also gone to great lengths to assemble “reference hydrological stations”, in catchments that have experienced relatively limited human change. Studies that used these sorts of stations in Australia, North America and Europe are all still consistent with our findings – namely that most stations show either limited changes or decreases in large streamflow events, depending on their location.

What can we say about future flood risk?

So what about the apparent contradiction between the observed increases in extreme rainfall and the observed decreases in large streamflow events? As noted above, our results don’t seem to be heavily influenced by changes in land use, so this is unlikely to be the primary explanation.

An alternative explanation is that, perhaps counterintuitively, extreme rainfall is not the only cause of floods. If one considers the 2010-11 floods in Queensland, these happened because of heavy rainfall in December and January, but an important part of the picture is that the catchments were already “primed” for flooding by a very wet spring.

Perhaps the way in which catchments are primed for floods is changing. This would make sense, because climate change also can cause higher potential moisture loss from soils and plants, and reductions in average annual rainfall in many parts of the world, such as has been projected for large parts of Australia.

This could mean that catchments in many parts of the world are getting drier on average, which might mean that extreme rainfall events, when they do arrive, are less likely to trigger floods. But testing this hypothesis is difficult, so the jury is still out on whether this can explain our findings.

Despite these uncertainties, we can be confident that the impacts of climate change on flooding will be much more nuanced than is commonly appreciated, with decreases in some places and increases in others.

Your own flood risk will probably be determined by your local geography. If you live in a low-lying catchment close to the ocean (and therefore affected by sea level rise), you’re probably at increased risk. If you’re in a small urban catchment that is sensitive to short sharp storms, there is emerging evidence that you may be at increased risk too. But for larger rural catchments, or places where floods are generally caused by snow melt, the outcome is far harder to predict and certain locations may see a decrease in flooding.

All of this means that a one-size-fits-all approach is unlikely to be suitable if we are to allocate our resources wisely in adjusting to future flood risk. We must also think about the effects of climate change in a broader context that includes changes to land-use planning, investment in flood protection infrastructure, flood insurance, early warning systems, and so on.

The ConversationOnly by taking a holistic view, informed by the best available science, can we truly minimise risk and maximise our resilience to future floods.

Seth Westra, Associate Professor, School of Civil, Environmental and Mining Engineering, University of Adelaide and Hong Xuan Do, PhD candidate in Civil and Environmental Engineering, University of Adelaide

This article was originally published on The Conversation. Read the original article.

Why warmer storms could lead to more flooding than expected


Conrad Wasko, UNSW Australia and Ashish Sharma, UNSW Australia

As the climate changes, we can expect more frequent and more extreme weather events, which will put pressure on our current infrastructure. It has been suggested that increasing temperatures will intensify rainfall, indicating that we are likely to endure bigger storms and more dangerous flooding in a future warmer climate.

Our study, published today in the journal Nature Geoscience, shows that this intensification in flooding may be even greater than expected. This is because of changes to the distribution of rainfall within storms – something known as the “temporal pattern”.

This study is the first to show that temperature changes are disrupting temporal rainfall patterns within storms themselves. When it comes to flash flooding, this is just as important, if not more so, than the total volume of rainfall that a given storm delivers.

If this trend continues with future climate warming, more destructive flooding across Australia’s major urban centres is likely. Because our findings were true across every Australian climate zone, ranging from tropical and arid to temperate, we can expect similar risks throughout the country, and conceivably elsewhere in the world too.

Looking to the past

Whether it is in politics, science or engineering, the past can be a good indicator of the future. Historical records of rainfall have long been examined for patterns to help us make sense of how the climate might change in the future.

By linking existing observations of rainfall intensity and temperature it has been found, in general, that we can expect more rainfall when temperatures are higher. This observation is founded in thermodynamics and underwritten by the Clausius-Clapeyron relationship, which states that for each degree Centigrade increase in temperature, 7% more moisture will accumulate in the atmosphere. It is not a large step to surmise from this that rainfall volumes will be 7% greater.

However, historical observations do not necessarily confirm this rate of increase – at least, not in a uniform way. Some places have experienced rainfall increases of more than 7%, while others have seen less than 7%.

This discrepancy is important. It suggests that changes in overall storm intensity are not the only change in rainfall a warmer climate may bring. There are other, more subtle disruptions we need to look for.

More flooding ahead?
Kate Wall/Newzulu/AAP Image

Finding the unexpected

In our study, we used historical data from 79 different locations around Australia, collected by the Bureau of Meteorology. This includes sites at each of the major capital cities, as well as regional areas in all states and territories. At each location we isolated storm events and then split each storm event into five segments, to determine the percentage of rain that fell in each. So, for example, a one-hour storm would be divided into five 12-minute segments.

By comparing the amounts of rainfall in each of these fractions to the average daily temperature at that location, we were able to check if there was any systematic relationship between the rainfall fractions within the storm and the ambient temperature.

Our results were unexpected. At every location, we saw that higher temperatures were linked to an increase in the largest fraction and a corresponding decrease in the smallest fraction. In other words, the storm pattern was less uniform and more erratic when the temperature was higher. Moreover, we found that these changes would increase flood peaks even if the storm volume remained unchanged, because more of the rainfall was concentrated into intense bursts.

Factor in the changes in overall storm volumes, which are also likely to increase with warming, and this is a recipe for more flood danger in areas including Australia’s urban centres.

Informing flood guidelines

So why is this important? Engineers Australia is in the process of rewriting the Australian Rainfall and Runoff guidelines, which dictate how we estimate potential flooding when designing infrastructure. Every structure, whether it be a roadside gutter, a bridge, or an office block, is built to withstand a flood of a given size and risk of occurrence. But if rainfall is changing, we need to plan for how we will design and build these structures to withstand the possibility of more destructive floods.

We need to make sure our infrastructure can handle the strain.
AAP Image/David Moir

Although history doesn’t necessarily have to repeat itself, the increase in non-uniformity linked to higher temperatures suggests that if temperatures increase we may see more increases in the destructive force of floods in the future. Planners need to consider whether the existing infrastructure that we take for granted every day needs added fortification to withstand the impacts of climate change.

The Conversation

Conrad Wasko is PhD Candidate in Civil Engineering at UNSW Australia.
Ashish Sharma is Professor, School of Civil and Environmental Engineering at UNSW Australia.

This article was originally published on The Conversation.
Read the original article.

Australia: Flooding and Climate Change


The link below is to an article that considers flooding in Australia and the impact of climate change.

For more visit:
http://www.couriermail.com.au/news/breaking-news/flood-plans-ignore-climate-change-expert/story-e6freono-1226602057544

Kiribati: Climate Change Threat and Floods


The link below is to an article reporting on the threat to Kiribati by climate change and flooding.

For more visit:
http://www.msnbc.msn.com/id/47432131/ns/us_news-environment/#.T7Nqt-hftnQ