PA cities have a sewer-system problem. Green infrastructure can help — but comes with its own risks

The densely populated Canadian city is tenth most at risk of flooding in the world as climate change raises sea levels. The government has instated a number of successful flood adaptation projects, with an ambition to become the “greenest city in the world."

Large cities like Vacounver and Seattle are increasingly leaning towards "green infrastracture," a method of managing stormwater through natural systems like green roofs and rain gardens that absorb rainwater. Cities have traditionally relied on traditional sewage systems, but in the face of climate change, and more intense storms, its proving to be inadequate. Green infrascture lowers flood levels, filters out pollutants in the water, and regulates city temperature. In Seattle, an early adopter of green infrastructure, rain gardens absorbed 1.5 trillion liters of rainwate.

While many communities in the Midwest use dams and levees to control the Mississippi River, some are trying new approaches to flood control as climate change threatens to increase rainfall and the severity of storms in the region. Some cities are turning to the Dutch solution of leaving “room for the river” to allow the body of water to flow naturally and design public spaces to handle inundation. While this technique doesn’t always work during major flooding events, traditional flood control strategies can be more harmful and actually worsen flooding.

Climate change adaptation efforts and economic development can go hand in hand, according to one Connecticut town. Meriden transformed a former mall into a large park, a natural solution that helps mitigate the town's routine flooding and has encouraged housing and retail development in the surrounding area.

After Hurricane Sandy wreaked havoc on the city, Hoboken, New Jersey decided to rebuild the city with climate change and increased flood risks in mind, rather than returning to "normal." With the help of federal funding - and their relatively well-off tax base - Hoboken is joining other East Coast cities in building climate resilient cities.

While some parts of the United States struggle with drought, others are faced with more water than they know what to do with. Minnesota reconstructs roads and drainage systems in order to be more prepared for the large amounts of rain fall they have received, largely due to climate change.

Zurich, Switzerland's largest city, is paving the way for sustainable building. Concrete is a major contributor of climate change due to the process it requires to make it. Zurich is making steps to reduce its use. A school building was constructed in 2002 with 80 percent recycled concrete. Three years later city officials passed a requirement that required all publicly-owned buildings to be made with recycled concrete and in 2013 ordered the use of CO2 reduced cement. According to a study the effort has saved 17,000 cubic meters of virgin materials.

After a river in Fiji continued to flood, an entire village relocated uphill 2 kilometers away. About two-thirds of the residents participated in this voluntary relocation, which proved effective when a strong cyclone hit the island. Government policies are making it easier for villages to relocate due to climate change; in fact, four have done so already. Balancing the people’s cultural connection to the land and the need to move can be tricky, but as people continue to be displaced, their responses could help inform other coastal communities around the world.

There are over 250 rivers and lakes that are shared between countries, accounting for more than half of world's freshwater. This means that countries have to cooperate to share resources. In 1972, Mali, Senegal, and Mauritania did just that. They formed the Senegal River Basin Development Authority, or the OMVS (for its French initials). In 2005, Guinea joined. The organization is an example of how countries can join forces to share water resources cooperatively.

Working toward environmental justice takes organizing on the community level. In Detroit, the Women of Empowerment promote resilience against the adverse effects of climate change on the city’s east side by spearheading projects that range from legal cases to the installation of solar panels. The group also partners with local nonprofits like the Eastside Community Network and Heatwaves Housing and Health (HHH), to collect data that can inform climate-resilient city planning.