Tsunami-resistant port planned for Crescent City after decades of natural disasters
In March last year, shifting tectonic plates off the coast of Tohoku generated a catastrophic tsunami that tore across Japan and travelled across the Pacific to the shores of America’s West Coast where the tiny port town of Crescent City sat in wait.
A humble community of around 8,000 people, Crescent City relies heavily on the smooth running of its harbour. Over the years the townspeople have become resigned to the danger their community faces from tsunamis; an earthquake in Alaska struck in 1964 creating a giant wave which destroyed large proportions of Crescent City and an 8.3Rs earthquake in the Kuril Islands in November 2006 generated a giant wave which rushed the port and caused major damage to its docks.
In March 2011, the earthquake off Sendai, Japan produced an immense tidal wave which sank 11 boats, damaged 47 more and flattened two-thirds of Crescent City’s docks. For the local residents this was the final straw and now funding has been made available to put measures in place to reduce the effects of future natural disasters.
The main issues at play lie under the waterline where the topography of the seabed around Crescent City magnifies the effects of a tsunami, focussing this colossal energy past the boundaries of the port. The deep ocean floor topography sees a convergence of force at Crescent City, enabling the exaggerated waves to rise up and batter moored boats.
In an article published by the Associated Press (AP) on 23 November 2012, Jeff Barnard explained that the ‘churning water rushes into the boat basin and then rushes out, lifting docks off their pilings, tearing boats loose and leaving the city’s main economic engine looking as if it has been bombed’.
After the city narrowly survived 34 tsunamis in 78 years, the authorities have released funds for measures that will make Crescent City’s docks tsunami-resistant. Unfortunately no human intervention can make a port entirely tsunami-proof however by taking certain steps to secure the docks and solidify the pilings, it is hoped that this modest Californian city will be able to endure these regular blows.
According to the AP, 244 steel pilings, 30 inches in diameter and 70ft long will be introduced to enhance the resilience of the docks. 30ft of this length will be sunk into the bedrock with approximately 18ft rising above the waterline to ensure that the docks will not be loosened during a tsunami attack.
A Pacific Ocean-wide tsunami alert system is already in operation with sensors detecting underwater wave action to catch potential natural disasters in time for effective evacuation prior to their impact with land.
In a paper issued in 2010 entitled Effects of Harbor Modification on Crescent City, California’s Tsunami Vulnerability, Lori Dengler and Burak Uslu examine how human intervention in the region may have unwittingly enhanced the damage to Crescent City’s port.
Their conclusion reads: “Our results suggest that modifications to the Crescent City Harbor have increased the peak currents produced by a modest tsunami such as the 2006 Kuril Island's tsunami by a factor of at least three within the small boat basin and near its entrance over the peak currents in the inner basin where boats were anchored before basin was built. This may have been sufficient to push the velocities over the threshold of damage.”
As experts continue to warn us of the effects of climate change, the threat of natural disasters continues to rise; it is imperative that we invest in the necessary technology and infrastructure to safeguard our cities to the best of our abilities, sharing knowledge and experience with similar regions across the globe.
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