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Maritime Container Shipping and Rising Sea Levels

bayonne bridge
The Bayonne Bridge, above, was recently raised; rising water levels might require the same adjustment for bridges on other port approaches (file image courtesy Jim Henderson)

By Harry Valentine 09-13-2020 03:45:54

Several studies undertaken internationally into the effects of changing world climate have focused on the warming Arctic region along with melting northern glaciers located across Northern Canada, Northern Russia and Greenland. While some studies suggest that world sea levels could rise by between 1.3 and 3-feet by 2100, other more alarming studies suggest that sea levels could rise by as high as 7-m or 23-feet. Both levels of rise of sea levels have potential to affect the future of container shipping.

While a rise in sea levels of up to three feet by 2100 would have little impact on the majority of container terminals internationally, a rise of over 20-feet presents some very serious implications for numerous container terminals and requires drastic action in terms of future planning in terms of terminals and ship technology. A rise in sea levels will increase the navigation depth and width of downstream areas of waterways. Some rivers that are presently non-navigable would become navigable to either extreme shallow draft vessels or to commercial river barges, along with future scope to dredge several such rivers.

The Small Increase

A three-foot (one meter) increase in seawater levels would increase channel navigation depth to allow deeper draft ships access to ports such as Hamburg, Newport News, Norfolk, Charleston, Savannah and Jacksonville. Such an increase would allow passage to slightly deeper draft ships to sail along the Russian side of the Arctic and allow slightly more heavily-laden ships to sail further upstream along such waterways as the Lower St. Lawrence River and Lower Mississippi River. However, the threat of coastal flooding caused by ship bow waves would require modifications to ships to reduce bow waves.

Recent advances in twin-hull vessel technology include specifically designed modifications to the bow area that redirect the bow wave under the vessel and between the twin hulls. Another possible method would involve the construction of a wide twin-hull technology that would attach to the bow of ocean-going ships of 105-feet beam prior to sailing upriver to a port such as Montreal. Special ducted propellers or paddle wheels would convert the bow wave to a fast rearward stream to flow between the main hull and the outrigger twin hulls so as to minimize erosion to riverbanks.

Inland Ports

A small number of container ports are located inland along navigable waterways and the list includes Hamburg on the Elbe River, Portland on the Columbia River, Fuzhou on the Wulong River, Guangzhou on the Shizi Ocean waterway and Montreal on the Lower St. Lawrence River. While rising seawater levels would provide greater navigation depth for deep-draft vessels, there would be need to reinforce riverbanks to prevent future riverbank erosion. With the exception of Montreal, all other aforementioned ports involve ships sailing comparatively short distances upstream from the ocean, justifying the expense of riverbank reinforcement.

While greater water depth along the Lower St. Lawrence River could transit deeper-draft ocean-going ships sailing between Quebec City and Montreal, the sailing distance of 140 miles exposes an extended riverbank distance to potentially accelerated erosion caused by large ocean-going ships sailing along the waterway. The high cost of reinforcing riverbanks between Montreal and Quebec City against future erosion would restrict the maximum beam of Montreal-bound ocean-going ships to 105 feet.

Bridges

Ships sail under a bridge on the approach to several major world ports. American ports include Port of Newark, Charleston, Savannah, Jacksonville, Philadelphia, Baltimore, Montreal, San Francisco and the north side terminals at Los Angeles. Internationally, ships sail under several bridges on the approach to Guangzhou and also to Montreal. Several years ago, in preparation to berth new generation Panamax size ships, the State of New Jersey raised the Bayonne Bridge to allow taller ships to pass beneath. Ships sailing from the North Sea to the Baltic Sea also sail under a bridge. 

Rising sea levels could require the scheduling of ships to sail under some bridges only at low tide, and some bridges could need to be raised in the manner of the Bayonne Bridge. Such may be the case for bridges at the entrance to the Baltic Sea, the bridges between Quebec City and Montreal, along with the Arthur Ravenel Bridge at Charleston and the Talmadge Memorial Bridge at Savannah. The combination of rising sea levels and larger future container ships would likely require that the bridge across the Suez Canal also be raised to higher elevation.

Waterway Modification

There are numerous non-navigable shallow streams and rivers along with seasonal streams that empty into the ocean. At the same time, some shallow draft vessels can sail in as little as one foot of water depth. Increasing water depth by between two and three feet invites dredging of some shallow waterways to support small-vessel navigation for some distance going upstream. Nations such as Bangladesh that depend heavily on waterway navigation would be able to extend the navigation season along their shallower and seasonal inland waterways, to the economic benefit of several towns and villages.

Rising sea levels would increase navigation depth along some shallow non-navigable waterways that with some minor dredging and levelling of the riverbed, would allow river barges to operate for some distance upstream and inland from the ocean coast, carrying containers and even bulk freight. To minimize possible riverbank erosion, there may also be need to use twin-hull vessels that redirect the bow wave to flow rearward under the vessel and between the twin hulls. Communities located along rivers in developing nations would likely benefit economically from development of waterway transportation indirectly caused by rising sea levels.

The Massive Sea Rise

Sea levels rising by as much as seven meters (23 feet) would be the subject of another article. A rise of two to three feet would be sufficient to affect ship movements at several world container ports. In cases such as Hamburg and Norfolk/Newport News, rising sea levels would make it easier for larger container ships to enter and leave these ports while at other ports such as Charleston, Savannah and Montreal, bridges under which ships sail could have to be raised to provide greater air draft.

Harry Valentine is a regular contributor to The Maritime Executive.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.