cities are, without a doubt, some of the greatest sources of human-induced environmental degradation around the world. the mass concentration of waste and pollution cities produce every day is incredibly alarming. despite these challenges, when designed holistically, cities also can provide some of the greatest opportunities for sustainable progress and development worldwide. moreover, if we want to ensure sustainable development and growth, it is essential that we prioritize urban efficiency and sustainability.  

cities’ importance in a sustainability context cannot be overestimated. around the world, metropolitan areas are emerging and expanding extremely rapidly — every day, there are approximately 200,000 people worldwide relocating to cities. this continuous trend of urbanization, one that has been consistent since the 1950s, means an additional 2.5 billion people (more than a third of our current global population) will be living in cities by 2050. the graph below, drawn from the un world urbanization prospects 2014 revision, illustrates this global trend.

how can we build smart cities?

without the proper guidance, incentives or regulation, city planners and municipalities, along with the business communities within them, can get away with employing unsustainable and detrimental development principles into their urban design mechanisms. many cities have fallen victim to this. atlanta’s 2.5 million residents, for instance, span over 25 times as much land and emit more than 10 times the transportation-related carbon emissions per capita as barcelona, a city of 2.8 million. barcelona’s success can be attributed to its vast concentration of various residential and business opportunities as well as its strong public transportation infrastructure, which incentivizes development within close proximities to the center of the city and discourages personal vehicle ownership.

for cities to properly accommodate an increasingly urban global population in an efficient manner, city planners and policy makers also must take into account the impacts of a warming climate on urban life. while in the near future — the timeframe in which it is imperative that we act — we cannot dramatically consolidate huge cities like atlanta, it is both necessary and economically optimal to rethink and improve their current infrastructure to ensure cities are able to withstand the effects of climate change. in order to do so, we must understand that cities and their components are part of a greater dynamic earth system, one that has been disrupted after years of irresponsible resource use and management. in understanding this, it is essential to recognize the holistic implications of urban design and development, with an emphasis on preemptively integrating climate mitigation strategies into urban design.

proper water management is key element

one such improvement is to integrate highly efficient rainwater storage and drainage systems along roadways, pavements, and green spaces in cities. just this past week, severe flooding devastated the east coast, and the economic repercussions are expected to be in the billions. as the global climate continues to warm, evidence suggests that the frequency and severity of intense storms are going to increase substantially. this is especially relevant to cities, as roughly three quarters of them, including some of the largest megacities in the world, are located on or very near coasts, where the impacts of extreme weather events, not to mention rising sea levels, will be most costly.

some urban developers and municipalities have already begun incorporating dynamic rainwater storage systems into their planning process in order to mitigate the impending effects of climate change. copenhagen, as discussed in its climate adaptation plan, has implemented many sustainable urban drainage systems (suds), which will significantly reduce the impacts of the projected increase in abundance and intensity of cloudbursts within the city. these systems retain rainwater locally by utilizing subsurface and roadside infiltration beds, permeable paving surfaces, and green roofs and spaces in order to minimize stress on sewage systems and wastewater plants.

(photo by darby mcglone)

smart water management models found today

skt kjelds quarter, a “climate adapted” neighborhood within copenhagen shown above, features large excavated green areas that are used for rainwater storage and contain highly absorptive plants. grated channels and permeable sidewalks surround the green space, as well as large rainwater storage tanks that are separate from the sewage system. the ground outside the space is also angled such that all rainwater is directed towards one of these retention systems in order to reduce the impact of flooding.

potsdamer platz, an urban district within berlin, is also tackling the issue of rainwater management and storage. following the fall of the berlin wall, the local municipality recognized the opportunity to reduce the impact of flooding by forcing the rapid influx of investors to sustainably manage 99% of the rainwater ​that falls on their property. sustainable management meant completely disconnecting from the previous combined sewage system and creating a more efficient and ecologically friendly rainwater capture, storage, and drainage system.

buildings within potsdamer platz are now lined with green roofs that capture more than 70% of incoming rainwater, cool and better insulate the buildings themselves, and send rainwater down pipes to reservoirs that greatly enhance the area’s biodiversity. the water in the reservoirs is then used to flush toilets, irrigate nearby green areas, and in some cases to supply buildings’ hot water or solar thermal systems, all of which saves the district approximately 20 million liters of water each year. among other feats, buildings within potsdamer platz utilize efficient ventilation, facade and passive cooling systems that, compared to conventional systems, cut primary energy consumption by half. there is also talk of using the algae and biomass that accumulate in the reservoirs to create biofuels.

systems like these aren’t the end-all solution for an urban sustainability transition, but they are tackling some of the most pressing issues facing cities today while preserving a valuable resource that is often overlooked. 

(image at top: potsdamer platz in berlin. / mijozi/wikimedia commons)