By the year 2050, close to seven billion people will be living in urbanized areas worldwide, which is almost double the number of urban inhabitants of today. Provision of adequate infrastructure service to this massive urban population in order to ensure their health, wealth, and comfort is going to be a daunting challenge for engineers, planners, and socioeconomic decision makers in the coming decades. However, the challenges faced by the developing and developed worlds are dissimilar in nature. While the developed world is coping with aging infrastructure, the developing world faces the challenge of keeping up with the brisk pace of urbanization and the consequential rise in infrastructure demand. In 2013, the American Society of Civil Engineers (ASCE) awarded the US infrastructure an overall grade of D+ and estimated that USD $3.6 trillion needs to be invested by 2020.1
When considering how to reshape, redesign, or create urban areas to be more sustainable, it is imperative to include urban infrastructure systems (UIS) in the decision-making process. UIS are durable features of the urban form and exhibit a strong form of path dependence. UIS have a pronounced effect on the general topology of the urban system and how the urban area continues to grow spatially over time. UIS, with a typical design life of 50 to 100 years, continue to dominate the urban form and mediate the citizens, goods, services, energy, and resource flows into, within, and out of the urban areas for decades after the design decision has been made. For example, transportation planning often has a prescriptive effect on the growth pattern of an urban region. Empirical estimates suggest that one new highway built through a central city reduces its central-city population by about 18 percent.2
It is also important to recognize that the use phase of UIS is the dominant contributor to the UIS impacts over the entire life cycle.3,4,5 Considering the dire state, massive demand, and relatively long lifetime of UIS, prudent choices need to be made to fit the requirements of a particular city according to its geographic location, demographics, climate. and needs. Keeping in mind the uncertainties arising from changing climate patterns, massive demographic shift towards urbanization and increasing resource constraint, it is imperative to ensure that future UIS development incorporate resilience as a key attribute in decision making.
Sustainability and Resilience: Definition and Need
There has been a recent impetus to incorporate sustainability in decision making. Unfortunately, in practice ‘sustainable development’ is often conceived in a narrower vision with the solitary goal of reducing resource investment (material and energy). This perspective of sustainable development precludes the incorporation of resilience in design and planning as ‘design for resilience’ often comes at a higher investment of resources. Resilience is an important attribute of sustainability, as it enhances the flexibility and adaptability of the system and increases the long-term benefits of material investments. In the context of urban infrastructure, resilience can be defined as the capacity to prepare for, withstand, and bounce back from any probable natural and anthropogenic hazard particular to the functionality of the system and location.
In addition, extreme weather events have been on the rise over the past few decades. These events are not only disruptive to human life, but are also responsible for significant economic loss. The National Oceanic and Atmospheric Administration (NOAA) estimates the economic losses caused by these events in 2012 will surpass that of 2011, which was pegged at USD $60.6 billion (adjusted to 2012 dollars).6
Building more resilient infrastructure systems requires that we develop the capacity to predict the range of stressors that need to be accommodated, their impacts, and ways to mitigate the impact of these stressors. Resilience can be achieved by enhancing the ability of a community’s infrastructure to perform under various stressors or through emergency response and other strategies that contain losses and allow communities to quickly return to pre-disaster functionality.7,8
Sustainability and Resilience: What Are Cities Doing
Many cities across the world have identified this adaptation challenge as an opportunity to evolve towards a more sustainable future through the development of sustainable and resilient infrastructure. An important clarification might be in order. ‘Resilience’ does not mean undertaking measures to safeguard the infrastructure or system from the last shock the system experienced. The following example can be considered to elucidate the fact. After the devastating terror attack on New York City in 2001, many property owners were concerned about potential threats from the air and placed generators underground. During Hurricane Sandy in 2012, that move met with disastrous results as most of those generators got flooded, thus disrupting the back-up power supply.10
Infrastructure resilience should be targeted towards increasing the adaptive capacity of the system so that it is able to prepare for and withstand a range of stressors, as well as bounce back rapidly to its performing capacity once the stressor(s) subsides. While natural and anthropogenic catastrophes cannot always be prevented, their effects can be mitigated through prudent design.
A recent effort undertaken in Venice, Italy exemplifies this approach in practice. Historically, Venice had a problem with high tides and flooding. With Venice sinking gradually at a higher rate than anticipated, and the rising of the Adriatic Sea, the combined effect is a 4mm (0.16 inches) rise in the sea level on an annual basis.
This means that by 2032, Venice could sink by 80 mm (3.2 inches) due to these combined effects.11 This challenge is compounded by the changing climate pattern and associated weather anomalies, with intense precipitation events, of particular concern to the city of Venice.
The MOSE project (Modulo Sperimentale Elettromeccanico, or Experimental Electromechanical Module) is intended to protect the Venetian Lagoon and the City of Venice from historically-occurring high tide events, as well as from the threats of a warming planet, which in all probability would lead to a rise in sea-level globally.
Started in 2003, the project is expected to be operational by 2017 and comes with a price-tag of approximately USD $7.3 billion.12 This project embodies a key aspect of resilient systems’ design: adaptability.
The MOSE is not being built only to address the recurring high tide issue of Venice, but would also augment the resilience of the city against potential sea-level rise from a warming planet. Instead of focusing just on the immediate issues, this approach enables the City of Venice to address issues that may potentially affect the city in the coming 50 to 100 years. In addition, the placement of 78 gates across 3 inlets allows for greater flexibility in operation to address stressors of varied magnitude.
The Cost of Resilience and the Role of Technological Innovation
While it is true that resilience augmentation more often than not requires increased up-front investment both in terms of resources (material, energy, and water) and financing, it pays a much greater dividend in the long run. First, estimates suggest that it costs approximately 50 percent more to rebuild infrastructure in the aftermath of a disaster than to build the infrastructure with the capacity to withstand that shock in the first place, notwithstanding the disruption to human life caused by the loss of service.13 Second, businesses are increasingly looking for more resilient places to set up their business, and consequently, the investment in resilience through the indirect and direct (during construction phase) creation of jobs.
The city of Pune, India offers an example of putting this idea into practice. Recurrent flooding has been one of Pune’s major worries. Anticipating the impact of changing climate patterns which have increased the frequency of intense rainfalls, the city has put into place a mix of technological and policy options to drive the city towards being more resilient against recurring flooding events. The city has also offered property tax incentives to encourage households to recycle wastewater or to store run-off rainwater for domestic use.14 This move has paid significant dividends to Pune. It has one of the lower vacancy rates among the Indian cities (on average about 10 percent lower) and analysts are unanimous that Pune has outperformed other Indian cities in terms of property appreciation and will continue to do so in the near future thanks to its ‘resilient Pune’ initiative.15
While typically it does cost more to be more resilient, technological advances can offer innovative solutions that can augment resilience without increasing the investment need, both in terms of resources and finances. A recent example from New York City (NYC) offers some interesting and innovative insights into this issue. The New York City Economic Development Corporation, in collaboration with Hudson River Park Trust, recently announced a competition, named ‘Change the Course,’ to invite innovative ideas to strengthen the ailing harbors of New York City in order to make the waterfront resilient in a sustainable manner. The winner of the competition was DShape, an Italian 3 D printing company. Quite literally, they are proposing to ‘print new infrastructure’.
DShape is the project of Enrico Dini, an Italian engineer who has spent millions of dollars and the better part of the last decade developing a printer that can print concrete. NYC is facing a problem that is typical for aging infrastructure: the pilings—wood or steel structures that support the piers at the NYC waterfront—are weathered from constant pummeling by storm surges, sea salt and natural wear and tear. Since these pilings are often buried more than 10 to 12 feet under the waterline, it is a very expensive proposition to repair them. The huge cost of repair is attributable to the complexity of underwater concreting to repair the piers.
With the use of 3D concrete printing, not only would it combine the best of precast and cast-in-place concrete, but would also lower the cost due to lower labor mobilization and quicker delivery and installation. Since these shapes would be prefabricated, the only underwater operation that is needed in this case is their placement, avoiding the cost of shoring, dewatering, and other procedures required to cast concrete under water. Consequently, it is estimated that applying this technology across the 565 miles of NYC shoreline would save the city USD $2.9 billion.16
While the application of 3D technology in addressing aging infrastructure at scale is still far from being mature, it shows that innovative applications of advanced technologies are promising in addressing sustainability and resilience of urban infrastructure at comparable or lower capital (resource and financial) investment.
Sustainability and Resilience: Do They Complement or Supplement Each Other?
As previously discussed, the premise of sustainable development is often distilled down to reduced resource investment. Unidirectional pursuit of this goal would require reduction of material and energy investment to the maximum extent possible, which would undermine the resilience of the system by eliminating redundancy or taking out some of the energy and material investments that make the infrastructures more robust. However, in the long run, this approach would be less sustainable because once these infrastructure systems are exposed to a natural or anthropogenic hazard they will have a higher probability of failure owing to their low resilience and would need to be replaced. This entails a far greater need for material and energy investment than what would have been required to incorporate some degree of resilience into the infrastructure systems in the first place, as discussed earlier.
However, there are technologies which address and augment sustainability and resilience simultaneously. Smart grids serve as a prime example of these kinds of technologies. A study conducted by Siemens, the Regional Planning Association, and Arup Consulting estimated that power loss for a day in NYC would cost USD $1 billion, in direct and indirect losses.17 The same study also estimated that the cost to repair NYC’s electrical grid from storms similar to Sandy could cost the city USD $3 billion over the course of the next 20 years. Investing the USD $3 billion in smart technology would reduce the probable cost of repair in the event of a hazard by USD $2 billion, and generate another $4 billion dollars from increased energy efficiency. Rerouting the investment to smarter technology from repair would eventually pay a 200 percent return on the investment. A smarter grid that allows for improved demand-response management would thus allow for greater integration of renewables into the system.
A smarter grid is also more sustainable (with a higher penetration of renewable energy) and resilient (with a more diversified energy mix and enhanced communication capabilities between the producer and the consumer). A large scale implementation of this approach is evident from the One Less Nuclear Power Plant initiative undertaken by the City of Seoul. Seoul accounts for approximately half of South Korea’s population and for 10.3 percent of the total power consumption in South Korea. That Seoul is heavily dependent on almost entirely fossil-fuel based, imported power (the self-sufficiency rate is only 3 percent) compounds the problem further.
While nuclear energy is one of the mature technologies which are not based on fossil fuel, concerns about its safety have increased both among the citizenry and decision makers in the wake of the Fukushima disaster. Whether nuclear energy is a safe and permanent option for moving away from fossil fuel based energy is a matter of discussion to be undertaken elsewhere and is beyond the premise of this discussion. Under these circumstances, Mayor Park Won-soon organized a citizens’ council to harness collective wisdom and ensure that policies reflect stakeholder preferences. The product that resulted from this citizen consortium was the One Less Nuclear Power Plant campaign.
This campaign consists of 71 specific projects in six policy categories, which are further categorized into 10 key action plans. Through this initiative, Seoul plans to install rooftop photovoltaic (PV) on approximately 10,000 buildings for a total capacity of 320 MW by 2014. Seoul will also install PV in idle spaces such as water and wastewater facilities, as well as public parking lots, which are expected to produce an additional 30 MW.
The city has also created a Seoul Solar Map which shows the potential of PV installation across the city, and is hosted on the city website to increase the participation of the citizenry. In addition to increasing the share of renewable energy in the mix, the campaign will also boost Seoul’s power self-sufficiency. The rate of power self-sufficiency is expected to increase to eight percent by 2014 and to 2o percent by 2020 under these policies. Furthermore, the aggressive energy saving measures are expected to reduce the energy demand of Seoul by about two million tons of energy, or ~22,000 GWh.18 A combination of these energy efficiency policies and integration of renewable energy is expected to result in a reduction of GHG emission by 6.06 Mt of CO2e.
One critical aspect to note in this initiative is how technological and policy tools were integrated to achieve the goal of energy self-reliance and progression towards a cleaner renewable energy mix. It is an imperative lesson that other cities and urban areas need to incorporate into their initiatives to progress towards more sustainable and resilient urban infrastructure systems. This initiative is also expected to pay rich dividends in terms of financial investment. It is expected to save the city around USD $1.5 billion from reduction in fuel imports as well as create approximately 35,000 recurring green-collar jobs.
This initiative undertaken by the City of Seoul clearly shows that there are indeed ways to augment both sustainability and resilience for the urban infrastructure, and earn rich returns on capital investment.
Sustainability and Resilience: Where Cities Need to Go
The 20th century urban infrastructure has been predicated on the seeming abundance of fossil fuels and with a Romanesque perspective, where the goal was to scrape off the natural ecology and replace it with engineered structures. The underlying rationale has always been that ‘engineering systems substitute natural systems,’ eluding to the notion that ‘engineering systems complement natural systems.’ Synergy of natural and engineered infrastructure, as in the case of Low-impact Development techniques for urban storm water management, is a classic example where they work in synergy to augment both sustainability and resilience.
The 21st century urban infrastructure needs to be sustainable and resilient to make it adaptable to rapidly changing climate patterns and increasing demands from a growing populations. In order to achieve the adaptability that will be required from modern infrastructure systems, the following six guiding principles are proposed:
- Design to prepare for, withstand, and bounce back from multiple hazards: Increasing resilience is not proofing the system from the last hazard it experienced. It is rather about increasing the capacity of the system to prepare for, withstand, and bounce back from a series of probable natural and anthropogenic hazards that the particular system might experience in terms of its location and functionality.
- Diversify the source of supply: Diversifying the source of supply for provisional infrastructure systems, like water and power, imparts greater flexibility to the system, in the sense that if one source fails, another can be used as back-up, thus increasing the resilience of the overall system.
- Integrate natural and engineered systems: Integrating natural and engineered systems incorporates more flexibility into the infrastructure systems in terms of its capacity to adapt to natural stressors. In particular, natural systems being more dynamic in nature respond better than engineered systems to long-term gradual stressors.
- Integrate technology and policy: Integrating technological and policy options are imperative to achieve any resilience or sustainability goal, in particular when implemented at the urban scale. Without proper policy tools, technologies have a rather feeble chance to succeed in terms of adaptation to scale.
- Engage citizenry in decision making: Policy decisions should be collaborative to harness the ideas from the citizenry and to incorporate the stakeholder preference into the decision-making process.
- Approach from a life-cycle perspective: Decision making in urban infrastructure often suffers from a lack of life-cycle perspective. Approaching from a life-cycle perspective would allow decision makers to realize the long-term dividends over the life-cycle that can be obtained from the initial investment for resilience. This is realized in terms of both financial and resource investments.
These six points are proposed as guiding principles for urban planners, designers, engineers and decision makers to steer the 21st century urban infrastructure towards being more adaptable, resilient, and sustainable. Also, it must be noted that when conceived from a life-cycle perspective, sustainability and resilience are indeed complementary and there are available mature technologies which can increase both sustainability and resilience of urban infrastructure systems.
This research was supported by the Brook Byers Institute for Sustainable Systems, Hightower Chair, and the Georgia Research Alliance at the Georgia Institute of Technology. The authors are thankful for a grant (#0836046) from the National Science Foundation program for Emerging Frontiers in Research and Innovation (EFRI). The views and opinions expressed herein are solely of the authors and do not reflect the views or opinions of the funding agencies.