Dredging Offers New Opportunities Globally

dredging

By Harry Valentine 2015-08-12 19:58:38

The recent opening of the expanded Suez Canal exemplifies the importance of dredging operations to maritime transportation and local economies. 

In recent years, the practice of dredging has faced mounting opposition from environmentalists who seek to protect the habitat of various maritime species. 

However, evidence from a major dredging operation that occurred at Cape Town, South Africa during the 1930’s suggests that marine environments quickly recover from major dredging operations. At the time, Table Bay was dredged to allow access to deeper draught ships and the dredged material was used to claim land from the sea.

The reclaimed land forms the basis of Cape Town’s very attractive foreshore business district. A variety of lobsters, harbor seals and harbor porpoises actually frequent the many partially enclosed dock and terminal areas of Cape Town’s old and new maritime terminals. Their presence indicates the presence of other fish species on which they feed. 

Environmentalists were in an uproar when the Emir of Dubai ordered the dredging of his principality’s coastline, to increase the number of waterfront residential accommodations. Whatever the short-term disruption to the local maritime environment, the new enclosed zones provide new maritime habitat.

While Holland and the New Orleans area of the United States reclaimed land from the sea by building seawalls and pumping out water, a major tropical storm on the Gulf of Mexico breached the seawall and caused major devastation at New Orleans. The low-lying region of Holland has had its share of flood damage caused by sea storms while the elevated reclaimed land at Cape Town has withstood many severe sea storms. There may be future opportunity to implement the Cape Town precedent at other locations internationally where there may be urgent need to increase land area.

New Offshore Islands

Much of the foundations of the new offshore island-based international airports at Tokyo and at Hong Kong benefitted from dredging operations that transferred suitable material from the seafloor to shallow water areas around pre-existing small islands. More recently, China has used dredging to transfer material from ocean floor to shallow water areas to construct new islands and to expand pre-existing small islands located in the South China Sea. While the Chinese project may generate international controversy, private companies may also dredge around small islands to create possible tourist resorts on enlarged islands.

Managing Water Flow

At the present time, there is a proposal to deep-dredge the lower Mississippi River in the southern United States, to allow ocean vessels of 105-foot beam and 27-foot draught to sail as far inland as Memphis. While the greater water depth has the potential to increase water volume flow rate, there are a variety of measures that can be implemented along the waterway to manage water flow volumes. One method is the inflatable bag that may reduce water depth at select location when inflated, then temporarily deflated to allow passage to a deeper draught of vessel.

A pair of such inflatable bags installed at a distance of one mile (two kilometers) apart under a designated navigation canal or channel can inflate and deflate in sequence to minimize water volume flowrate while allowing passage to larger vessels that can sail at constant speed. The dredging operations would focus on a designated navigation channel, likely only causing a temporary disruption to aquatic wildlife habitat on the riverbed. 

Candidate Rivers

Changing conditions in several nations has reduced water volume flow rate along rivers, either minimizing the volume of water that flows into the ocean, or even eliminating such flow rate altogether.

There are also the mouths of seasonal streams and rivers located around the coast of the Middle East, North Africa and even parts of Pacific South America and Australia. Many years ago an earlier government of South Africa introduced Eucalyptus trees from Australia, into swamp lands as a measure to reduce reproduction of problematic insects such as mosquitoes. However, the prolific water consumption of the Eucalyptus trees dried out several swamps and rivers that had once flowed to the sea, allowing potential to dredge several former riverbeds going inland from the sea to create seawater inlets and tributaries.

Construction of storage dams along rivers such as the Tigris and Euphrates has greatly reduced the volume of water that reaches to sea, affecting both fish habitat as well as eliminating navigation. A precedent from Canada’s Lower St Lawrence River illustrates a future dredging possibility, given that the riverbed at the Port of Montreal is actually below maritime sea level, with near constant navigation depth of 10-metres over a distance of 150-miles (240-kilometers) between Montreal and Quebec City. It is possible to combine that precedent with the very recent dredging precedent of the new section of Suez Canal.

New Inland Ports

Several years ago, the King of Jordan proposed a dredging project inland from the Gulf of Aqaba, to bring maritime traffic further inland and to provide a source of ocean water to maintain water levels in the Dead Sea that is presently evaporating. There is potential to dredge several seasonal streams that flow through the lowland areas in the Middle Eastern Emirate region, to provide additional waterfront property for residential and hospitality accommodations as well as navigable waterways for pleasure craft and small commercial watercraft. Dry riverbeds occur in the lowlands of the Western and north-eastern Sahara region.

A future discovery of a marketable ore or oil in the lowland Western or North-eastern Sahara could prompt an economic evaluation of a possible major dredging project that could extent inland for up to 200 miles (300 kilometers.) Smaller dredging projects that provide passage to small watercraft could help develop new upscale residential districts as well as attractive tourist destinations that could include a dredged or excavated inland lake with an underwater barrier at its entrance to keep out sharks. Dredging inland from the coast could create seawater runways that would be protected from waves, for seaplanes and ground-effect craft.

Conclusions

Despite opposition from environmentalists, ecosystems eventually recover and/or adapt after dredging. In the case of the Suez Canal, dredging produced an entirely new navigation channel and otherwise inflicted none to minimal damage to the natural environment. 

In the case of channels that are dredged going inland from the sea to produce an inlet, there may be need to also develop methods by which to assure a continual exchange of water. In some cases, minimal water flow from an upstream source could achieve that result. There are many locations internationally where new dredging of waterways could produce positive results.

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