Avoiding disasters in urban environments

This section describes vulnerabilities that urban environments face which can lead to disasters, and asks whether disasters in urban environments can be avoided. The number of people living in urban environments continues to rise, which increases the number of people exposed to potential hazards.

As our section on Defining a Disaster outlines, disasters do not come from nature, they come from the choices we make to live and build in harm’s way, and sometimes to force people into harmful situations, or do nothing about it if they put themselves in such situations. As a result, the impact of these hazards can be devastating.

Intense periods of heat exact a heavy toll on communities. Raging wildfires can lead to lives lost and lives ruined, with major smoke haze and pollution problems causing long-term health problems. Hurricanes, cyclones and typhoons take lives and wreck livelihoods. Heavy rains and sea storm surges paralyse societies. Earthquakes can instantly destroy swathes of urban areas. Drought forces cities and towns into desperate measures. Cold snaps such as "cyclone bombs" cause major problems. Responses to microbial pathogens can shatter our norms, as can letting the pathogen run rampant - as we have seen with COVID-19. The social, economic and environmental impact of such situations is huge, whichever choices are made. 

Despite all the challenges and problems facing urban environments, there is still optimism and room for hope. Many groups of people are taking action to reduce vulnerabilities and avoid disasters. 

Many cities and towns around the world are located next to the sea or the ocean, or on a major river – and for good reason. Waterways have been pivotal to trade and commerce for centuries. As they expand, these urban areas can face an increasing threat from coastal and inland flooding. 

The resilience of cities and towns located next to the ocean or the sea against rising sea levels is of pressing importance. Reports and research released over the past few years indicates that many of the world’s largest urban hubs face increasing risks of extreme sea level events such as storms and hurricanes with climate change influences being one factor among many. 

From Alexandria to Bangkok, Basra to Ho Chi Min City, Miami to Mumbai, Shanghai to Venice, the threat is growing. And not only in the world's major centres - it is a growing threat for many small towns too. 

We do not know exactly how fast or how high sea levels will rise, because much depends on taking action to stop human-caused climate change, but there is general agreement on the impact it is having: submergence and flooding of coastal land, saltwater intrusion into surface waters and groundwater, increased erosion of land and the built environment and a range of interconnected negative social and economic consequences. The consensus amongst experts is that these effects will be widespread, and they may accelerate over time. 

Whilst some coastal cities could be submerged under some scenarios without any action, most will not be. All coastal cities and towns must think through their specific flooding risks, which includes examining the fabric of the built environment that exists on the coast and what is at risk, and how this built environment is forecast to change over time. They need to anticipate problems and agree how to introduce the right kinds of measures to be resilient against flooding. Building human-made sea defence walls is only part of the solution. Other flood management should be considered, including supporting ecosystems with floodplains. Many natural defences such as sea grass and mangroves were stripped away in the name of development, and this approach needs to be reversed.

In coastal towns and cities, lower-cost housing is often located in low-elevation districts that are vulnerable to flooding and storm surges. This type of housing tends to be (though not always) of poor quality, with structural problems and inadequate maintenance adding to the pressures of land vulnerabilities to flooding. Even relatively small events can have huge consequences on the households of these areas, damaging people’s belongings, disrupting utilities, contaminating water and creating other negative health impacts. Their livelihoods can be taken away from them in an instant. Those who live in these areas are often more vulnerable, with low incomes and few financial assets, little say or influence in how things are run, and they are often not connected to sources of information about disaster recovery aid either. In certain parts of the world, programmes are in place to relocate people from such vulnerable areas.

The lack of ecological solutions, built environment vulnerability, socioeconomic vulnerability and lack of governance add up to pressures on these areas that will only increase over time if action is not taken to address the challenges proactively, and to avoid a disaster before it has the chance to happen.

Rather than plan for a “once in a 100-year, 1,000-year or 10,000-year storm or flooding event”, city and town administrations should use science-informed data from their local area to plan for long-term resilience against flooding (and other risks) – learning from past events and experiences in other regions. How many near misses of flooding events have they experienced, and do they routinely learn from such near misses? Proactive actions are likely to be less costly than the cost of disaster recovery.  

Good governance by cities and towns needs sensible zoning regulations, such as exclusion of building development in floodplains. In too many cases in developed and developing economies alike, buildings are being erected in flood-risk areas. Should proposals for new property development be declined, whilst noting that such land areas are often priced at a premium? 

Physical system changes made in small, quick and tactical ways in cities and towns can go a long way towards protecting them against the worst effects of flash flooding. For example, when it is feasible for sidewalks / pavements and roads to be repaired / replaced, could “permeable pavements” be used rather than hard surface materials? Greenery soaks up rainfall, so introducing more greenery (which of course has many other benefits) can help reduce flood risk - as long as it is well managed through the use of native species and good engineering, not forcibly displacing people, and ensuring that accommodation is still affordable for people. Green roofs help soak rainwater  and help prevent it from running down drainpipes and adding to the pressure on urban drainage and stormwater systems. Rainwater and sewer systems need to be kept free of rubbish and trash to prevent blockages by litter and debris. In this case, simple measures such as  frequent trash collection, easy access to areas of trash disposal, and public education can be part of a coordinated plan to improve flood resilience and minimise flooding impacts.

From Australia to Chile to Spain to the USA, a great deal of work is being done in countries around the world to minimise risk and address vulnerabilities towards wildfire - in urban areas and also rural areas where so much devastation can take place. Yet, with each fire season, we continue to see devastation and tragedy across the world in both urban and rural areas. 

In areas where there is a high wildfire hazard, improvements in land use planning  can reduce fire risks to homes and communities by for example restricting the construction of new developments in fire prone areas  Continuous awareness of the risks and being alert to the dangers is key. As with other types of disasters, good warning systems and testing of such measures is vital.

For individual homeowners, building a home with wildfire in mind can increase a home’s survivability. Using wildfire-resistant building materials in the construction of a home can reduce vulnerabilities and opportunities for ignition. Managing vegetation immediately surrounding a home reduces the potential for a home to ignite during a wildfire.

This piece from the C40 group, published in 2021, discusses how to protect urban lives, health and property from wildfire.

An example of land use planning activities that can minimise the risk of wildfires is available in this piece by Headwaters Economics (scroll half-way down to see a useful diagram).

For some urban places, the threat of earthquakes, tsunamis and volcano eruptions looms very large indeed.

Some cities and towns, including Christchurch, Jakarta, Kathmandu, Istanbul, Manila, Osaka, San Francisco and Tokyo are situated in known earthquake risk zones. The one thing they can do is prepare. Earthquake scientists estimate, for example, that there is a 72 per cent probability of a magnitude 6.7 or greater earthquake in the San Francisco Bay Area in the near future.​​​ 

Underwater volcanic eruptions can create tsunamis and risk severing subsea telecoms and Internet cables, which could have a major impact on affected urban areas. The more remote parts of the world, such as some of the worlds’ Small Island Developing States (SIDS) may struggle to find financial resources for back-up subsea cables to be in place, meaning that if it occurs, then they could be cut off for some time (for example, Tonga was cut off from the Internet for about five weeks). What kind of planning can be done to prevent a major problem if this happens? Many cities are situated quite close to above ground volcanoes. Some have been dormant for a long time, others are active. In addition, a large volcanic eruption can cause widespread cross-continent disruption to air travel and potentially cause ash to settle over a very large area, affecting agriculture and people’s breathing.

As an interview with the expert Michel Bruneau describes, a key factor to avoiding a disaster when an earthquake occurs is good construction of the built environment, to recognised building codes and structural and civil engineering standards. When governance fails to ensure the right construction is applied, disasters occur.

It is also important for all groups of people involved in thinking about earthquake disaster prevention to agree "what a good outcome is". For structural engineers, a good outcome could be that buildings do not fall down, but, as has been seen in some cases around the world, if this is achieved but the buildings then have to be pulled down and spaces sit empty for months, that is not a good societal outcome for a community.