The Longest Floating Bridges in the World: Engineering Marvels Over Water
Floating bridges, also known as pontoon bridges, are unique engineering feats designed to span large bodies of water where conventional bridge foundations are impractical. These bridges rest on buoyant pontoons rather than fixed supports, making them ideal for deep waters, shifting seabeds, and earthquake-prone regions. In this article, we explore the longest floating bridges in the world, showcasing their history, construction, and significance.
1. Evergreen Point Floating Bridge (SR 520 Bridge) – USA
Length: 7,710 feet (2,350 meters)
Location: Washington, USA
The Evergreen Point Floating Bridge, also known as the SR 520 Bridge, is the longest floating bridge in the world. It spans Lake Washington, connecting Seattle to the city of Medina. Opened in 2016, this modernized structure replaced the older bridge from 1963. Designed to withstand strong winds and earthquakes, it includes intelligent transportation systems (ITS) and high-occupancy vehicle (HOV) lanes, improving traffic flow and safety.
2. Governor Albert D. Rosellini Bridge (I-90 Floating Bridge) – USA
Length: 6,620 feet (2,018 meters)
Location: Washington, USA
Commonly referred to as the I-90 Floating Bridge, this structure links Seattle to Mercer Island over Lake Washington. Built in 1989, it replaced an earlier bridge from 1940. The bridge carries heavy commuter traffic, supporting both vehicle lanes and pedestrian paths, and plays a vital role in Seattle’s transportation network.
3. Hood Canal Bridge – USA
Length: 6,521 feet (1,987 meters)
Location: Washington, USA
The Hood Canal Bridge is the longest saltwater floating bridge in the world, connecting the Olympic Peninsula to Washington’s mainland. Originally constructed in 1961 and rebuilt in 1982 after a severe storm, it provides crucial access to the region. Unlike other floating bridges, it features a drawbridge section that allows ships to pass through.
4. Third Lake Washington Bridge (Lacey V. Murrow Memorial Bridge) – USA
Length: 6,620 feet (2,018 meters)
Location: Washington, USA
Parallel to the I-90 Floating Bridge, the Lacey V. Murrow Memorial Bridge is another remarkable structure spanning Lake Washington. Originally built in 1940, it was partially destroyed in a storm in 1990 and later reconstructed. This bridge is a key part of the Seattle metro area’s transportation network.
5. Nordhordland Bridge – Norway
Length: 5,295 feet (1,614 meters)
Location: Norway
The Nordhordland Bridge is Norway’s longest floating bridge, linking Bergen to Nordhordland across the Salhusfjorden. Opened in 1994, this hybrid bridge features a floating pontoon section combined with a cable-stayed segment, allowing ships to pass freely beneath. It has significantly improved connectivity in the region.
6. Don Burnett Bicycle-Pedestrian Bridge – USA
Length: 4,910 feet (1,497 meters)
Location: California, USA
Though smaller than others on this list, the Don Burnett Bridge is notable for being one of the longest floating pedestrian and cycling bridges. Located in Silicon Valley, it provides an essential non-motorized crossing over Stevens Creek, enhancing urban mobility and sustainability.
7. The Jiaozhou Bay Floating Bridge – China (Honorable Mention)
Length: 26.7 miles (43 kilometers) (Not a true floating bridge)
Location: Qingdao, China
Although not a true floating bridge, the Jiaozhou Bay Bridge in China deserves an honorable mention due to its length and water-crossing nature. It is one of the longest cross-sea bridges in the world, featuring both a beam bridge and a floating causeway section.
Why Are Floating Bridges Built?
Floating bridges are constructed in locations where deep waters, unstable seabeds, or seismic activity make traditional bridge foundations difficult or costly. The primary reasons for building floating bridges include:
- Deep Water Challenges: Conventional pillars would be too expensive or structurally impractical.
- Environmental Considerations: Floating bridges minimize seabed disruption, protecting marine ecosystems.
- Flexibility & Durability: These bridges can be expanded, repaired, or replaced more easily than fixed structures.
Floating bridges represent the perfect blend of innovation and necessity, allowing transportation infrastructure to overcome geographical challenges. From the record-breaking SR 520 Bridge in Seattle to the ingenious Nordhordland Bridge in Norway, these structures are critical for regional connectivity and economic growth.
As technology advances, we can expect longer, more resilient floating bridges that push the limits of engineering while ensuring environmental sustainability.
Interested in more engineering marvels? Stay tuned for more deep dives into the world’s most fascinating bridges!
