Waterway Dredging

(Source: U.S. Army Corps of Engineers)

The National Ocean Service defines dredging as, “the removal of sediments and debris from the bottom of lakes, rivers, harbors, and other water bodies. It is a routine necessity in waterways around the world because sedimentation—the natural process of sand and silt washing downstream—gradually fills channels and harbors.” Typically, dredging is not a controversial process as it is used to maintain or increase the depth of major navigation channels for safe passage of massive boats engaged in the importing or exporting of goods from a country. Dredging may be construction (the removal of materials to facilitate new navigation channels or water projects, such as locks or dams) or maintenance (the periodic removal of accumulated sediment from navigation channels and harbors to maintain authorized depths and widths) (National Ocean Service, 2017).

A second type of dredging that is performed is referred to as environmental dredging. It is designed to reduce the exposure of fish, wildlife, and people to contaminants and to prevent the spread of contaminants to other areas of the water body. This may be viewed as necessary in circumstances in which pollutants have been introduced into waterways from sources such as sewer overflows, municipal and industrial discharges, and spills, or from sources such as runoff and atmospheric deposition (gases and particulates released into the atmosphere from combustion sources such as automobile emissions that fall into waterways directly or indirectly as they are washed off roofs and other hard surfaces). Whatever the source, these pollutants threaten aquatic life (especially bottom-dwelling organisms and fish - and their consumers). These dangers are most likely to occur near cities.

     A third reason that dredging may occur is to widen or deepen waterways in order to facilitate passage of recreational boats (or larger recreational boats). This may involve the dredging of channels through bars at the entrances of coastal creeks and rivers to provide access to public boat launching and landing facilities and to connect creeks and inlets to deeper water (to enable larger boats).  This dredging of naturally occurring waterways for recreational purposes is often controversial because many people believe that facilitation of larger boats is not an adequate justification for the possible environmental and community harms and high ongoing costs that often follow.

(Source: Archives of Pearson, Scott, Foreman)

Dredging these smaller waterways can produce four types of harm that must be weighed when considering the benefits to recreational boaters.

 

     1Environmental harms

 

          * The soil deposits in any water-body have a certain predisposed composition. Dredging alters this composition. Due to this alteration, the existing habitat of creatures and organisms that depend on the original composition of the soil may die out, and aquatic ecosystems may be disrupted.

          * The turbidness (the stirring up and possible suspension of sediment) of the soil under the water also changes because of this alteration in underwater soil composition. This poses problems by way of creation of newer and harmful organisms, transferring of unwanted organisms to other parts in the water-body leading to a wider spread of contamination and organic processes by way of release of extra and unwanted nutrients. There may be interference with the spawning of marine life. The turbidness also causes the already existing contaminants to spread further into the water-body which also affects the marine environment adversely.

          * Harmful secondary impacts to marsh productivity and tertiary impacts to marine life may occur.

          * There may be unacceptable environmental impacts on upstream waterway ecology – such as salinity penetrating further inland.

          * Possible contamination of dredge spoil sites (the sites where the dredged materials are deposited). The nature of dredging operations and possible environmental impacts cause the industry to be closely regulated. The U.S. Clean Water Act requires that any discharge of dredged or fill materials into waterways, including wetlands, is prohibited unless authorized by a permit issued by the Army Corps of Engineers. This process focuses solely on potential negative impacts to the environment. In addition, the U.S. Environmental Protection Agency provides oversight and authorization for the disposal of dredged materials (National Ocean Service, 2017).

A study in West Virginia reported:

Dredging has both short and long-term effects on the natural and human environment. Some or all of the following may occur during or after dredging operations: • increased water flows downstream and increased flooding, • disturbance caused by vehicle and equipment access, • destruction of stream bank and aquatic vegetation, • disruption of the aesthetic values of the stream corridor, • removal, release, or rearrangement of sediments, • reduction of water quality, • remobilization of contaminants, • increased turbidity, • lowered water tables, • increased erosion and sedimentation, • alteration of hydrology, • alteration of hydraulics (current patterns and flow), • increased bank instability and erosion, • alteration of  fish habitat, • alteration of fish spawning habitat, • alteration of benthic (the flora and fauna found at the bottom of a body of water or in the bottom sediment) habitat, • disruption or removal of benthic communities, • reduction in height of high frequency, low- level flood events over the short term unless it is properly maintained, and • false sense of security following dredging (West Virginia Conservation Agency, 2017).

 

     2. ​High costs

          * The costs associated with studies required to get a permit are very expensive.

          * The capital costs of a dredging operation are very expensive.

          * Benefits gained in the short term are usually soon lost through siltation and shifting banks. This means that once a waterway is dredged, it will need to be dredged periodically in the future – thus adding more cost. “In North Carolina there are two types of federally authorized channels or inlets: deep draft inlets (which have more than a 15-foot depth) and shallow draft inlets (which have a 15-foot depth or less). The two deep draft inlets in North Carolina are Wilmington Harbor and Morehead City. Historically, deep draft inlets have not been an issue in North Carolina. It is shallow draft inlets that are a concern due to their tendency to shoal (development of sand or other material that rises from a body of water to near the surface; these may impact navigability of the water rapidly” (Lesher, 2015).

 

     3Alteration of community ambience – the introduction of more and larger boats can change a small, quiet community into a more bustling, commercial community. Smaller water enjoyment activities (paddleboards, kayaks, canoes, etc.) are more difficult in areas with more boat activity especially if they are large and fast boats (KaranC, 2016; Maritime Safety Queensland, 2017).

 

     4. Harmful unintended consequences. It is not always possible to anticipate consequences of dredging as the state of Florida learned in one of its dredging programs.

Florida’s coastal population growth and urban development have been driven in part by the creation of the Intracoastal Waterway System to facilitate vessel navigation…Canal systems, originally dredged to create land for homes, have become de facto transportation systems linking tens of thousands of residential boat docks to the ICW and to deeper water in the Atlantic Ocean and Gulf of Mexico. Naturally occurring deeper channels, dredged waterways, and canal systems are also preferred by manatees as migratory routes and travel corridors to feeding areas and, in the case of residential canal systems, as “safe havens” and important sources of freshwater discharge” (Bayside Cape Coral, 2017).   

 

These natural and human created conditions contribute to a greater chance of collisions between manatees and boats – a significant cause of manatee deaths in Florida…In addition, the alteration of wetlands by dredge and fill operations, channelization of rivers and streams, and other changes to freshwater flow also threaten the habitat that manatees rely on for survival (Manatee Awareness and Protection Program, 2007). The Florida manatees have lived in the state’s waters for about 12,000 years, while their ancestors were here for over one and a half million years. Manatees are a federally listed threatened species and are protected by the State of Florida (Bayside Cape Coral, 2017).

(Source: Manatee Awareness

and Protection Program)

(Source: Manatee Awareness

and Protection Program)

What Can Be Done?

 

The starting points for doing something about the dredging of naturally occurring waterways in Brunswick County is the same as with all of the environmental issues covered in this section of the website:

  • Become more knowledgeable about this issue.

 

  • Discuss this issue with others; learn from them and help them learn from you.

 

  • Join forces with groups and organizations that are knowledgeable about environmental issues in general (BEAT!) and about this issue in particular. Organizations have greater access to scientific expertise, have larger budgets, have more contacts with the media, and have the force of combining many voices into one.

 

  • Advocate for policies that show understanding and respect for natural processes. Examples are educating the general public and government officials about the harms associated with dredging naturally occurring waterways in general and especially in situations where the only justification is enabling large recreational boats to gain access to deep water and to identifying local marinas where large boats can be housed.

 

  • Advocate for government agencies and government leaders at all levels to strive to fulfill their responsibilities toward protection and conservation of the environment.

 

  • Examine the values and political position on this issue of candidates running for political office. Federal support for a strong Environmental Protection Agency is very important. Support for a meaningful Department of Environmental Quality in North Carolina is very important. Support by North Carolina’s governor and state legislature for taking a scientific approach to consideration of naturally occurring waterways is absolutely critical. Look for candidates that emphasize the importance of environmental impact in making decisions about what to do or not do.

References

 

Bayside Cape Coral. 2017 “Florida Manatee.”

www.baysidecapecoral.com/manatee.html

 

KaranC. 2016 “Effects of Dredging on the Marine Environment.”

www.marineinsight.com/environment/effects-of-dredging-on-the-marine-environment/

 

Ben Lesher. 2015 “Coastal Dredging in North Carolina.”

www.ced.sog.unc.edu/coastal-dredging-in-north-carolina

 

Manatee Awareness and Protection Program. 2007 “Effects of Coastal Development.”

www.flmapr.com/dock.html

Maritime Safety Queensland. 2017 “Dredging for Recreational Access.”

www.msq.qld.gov.au/Waterways/Recreational-boating-infrastructure/Dredging-in-Queensland)

 

National Ocean Service. 2017 “What is Dredging?”

www.oceanservice.noaa.gov/facts/dredging.html)

 

West Virginia Conservation Agency. 2017 “Dredging and Stream Channel Restoration.”

www.wvca.us/flood/pdf/14_Appendix_H_Dredging_and_Stream_Channel_Restoration.pdf

Read and See More on the Dredging of Naturally Occurring Waterways
 

George Monbiot. “Dredging Rivers Won't Stop Floods. It Will Make Them Worse.” 2014

www.theguardian.com/commentisfree/2014/jan/30/dredging-rivers-floods-somerset-levels-david-cameron-farmers

 

      Brief discussion of the many concerns that accompany dredging.

New York Department of State: Dredging: Is it a Good Solution to Flooding Problems?” 2012
www.fws.gov/northeast/nyfo/USCA/Dredging_Factsheet.pdf
 
     Written in 2012, this analysis concludes that dredging may increase the likelihood of nearby flooding and often creates more problems than it solves.
 
Trista Talon. “Sunset Beach Studies Plan to Dredge Canals.” 2016 www.coastalreview.org/2016/09/sunset-beach-studies-plan-dredge-canals/

     A September​, 2016 article in The Coastal Review that describes some of the early issues in the Jinks Creek controversy.

(Sample Scholarly Article): Paul L.A. Erftemeijer and Roy R. R. Lewis. 2006 “Environmental Impacts of Dredging on Seagrasses: A Review.” Marine Pollution Bulletin 52:1553-1572. www.sciencedirect.com/science/article/pii/S0025326X06003778

     A review of 45 cases worldwide demonstrates the importance of studying the effect of dredging on the health of seagrasses on a case-by-case basis. Study finds that seagrasses have often been harmed by dredging, but that tighter control in the form of strict regulations, proper enforcement and monitoring, and mitigating measures together with proper impact assessment and development of new environmental dredging techniques help to prevent or minimize adverse impacts on seagrasses.

(Sample Scholarly article) D.S. van Maren, T. van Kessel, K. Cronin, and L. Sittoni. 2015 “The Impact of Channel Deepening and Dredging on Estuarine Sediment Concentration.” Continental Shelf Research 95:1-14. (www.sciencedirect.com/science/article/pii/S0278434314003720)

     Channel deepening appears to be a main factor for increasing the transport of sediments up-estuary, due to increased salinity-driven estuarine circulation, and suspended sediment concentration.

 

(Video) “Sand Dredging on the Grand Strand of South Carolina.”

www.youtube.com/watch?v=F8seUSIEKGY

 

     Video of Myrtle Beach’s effort to dredge the ocean floor for sand to renourish its beach.

Sample of Scholarly Journals:

  • Bioscience

  • Journal of Environmental Management

  • Journal of Marine Science

  • Marine Pollution Journal

  • Maritime Journal

  • Oceanography and Marine Biology Annual Review

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