Movable flood barriers
Movable flood barriers are innovative structures designed to protect communities from flooding caused by rising sea levels and extreme weather events. Unlike traditional rigid flood control systems such as dikes and levees, these barriers can be deployed or retracted as needed, allowing for more flexible responses to flooding threats. Developed in response to catastrophic floods in the mid-20th century, such as those in the Netherlands and England, they play a crucial role in modern flood management strategies.
Notable examples include the Oosterscheldekering and the Thames Barrier, both of which feature advanced engineering designs that allow them to be activated based on real-time water level data. The Delta Works in the Netherlands exemplifies a complex system of movable gates that can be closed to block tidal surges during storms. In Italy, the MOSE project aims to protect Venice from flooding, though it has faced environmental concerns and construction delays.
As climate change accelerates sea level rise, the importance of such barriers has become increasingly evident, prompting ongoing discussions about their design, effectiveness, and environmental impact. These structures not only serve as critical defenses against flooding but also reflect the adaptation efforts of cities facing the realities of a changing climate.
Subject Terms
Movable flood barriers
Definition
People have innovated technology and methods to divert floodwater throughout history. Devices to block excess water from inundating land include dikes, levees, and seawalls, which are primarily rigid structures. In the twentieth century, extreme floods overwhelmed many of those structures, prompting people to seek better protection to withstand future deluges. Engineers designed large movable floodgates placed at intervals in rivers and lagoons adjacent to seas. These barriers, which could be quickly maneuvered into place for specific flooding threats, were constructed from more durable materials and in greater sizes than previous flood walls. When sea levels rose, producing surges, operators raised and closed movable barriers to keep rising seawater from flooding communities. After conditions improved, barriers were opened or lowered to enable water traffic to pass unimpeded.
Significance for Climate Change
Raised seawater levels associated with global warming often result in severe flooding in coastal communities. European floods in 1953 were especially catastrophic. Government leaders in England and the Netherlands, which both suffered vast losses, sought more effective ways to control flooding. The 1953 floods resulted in engineers in the Netherlands developing the innovative Delta Project to control flooding with a complex system of heightened dikes, connected seawalls and dams, and movable floodgates that could be shut into position when storms occurred to block tidal surges from the North Sea.
The Delta Works consists of some of the Earth’s biggest movable flood barriers. Beginning service in 1986, the Oosterschelde Barrier, built in an estuary, contains sixty-two steel gates that move on concrete piers. Saltwater necessary to sustain the estuary’s ecosystem can advance through the opened gates. Built by 1997 at Rotterdam, the Maeslant Storm Surge Barrier on the Nieuwe Waterweg incorporates computer sensors that sense rising water levels from tidal surges and activates the two curved triangle-shaped gates to pivot from their home bank to meet in the river’s center. The movable Hagestein Weir near Hagestein, Holland, has curved gates resembling visors that can be shut to control water flow.
In England, the Thames River represented that country’s greatest flood concern, particularly in London. Officials considered reports suggesting building a river-wide barricade consisting of gates that could be moved to impede floodwater. They passed the 1972 Thames Barrier, and Flood Protection Act. Construction of a movable flood barrier started in 1974 at an east London site located in the Thames Estuary. By 1982, builders finished the Thames Barrier, which consists of ten hood-shaped steel gates mounted on concrete sills secured to the river floor. Environment Agency personnel oversee the Thames Barrier and evaluate tidal threats based on Storm Tide Forecasting Service data and computer models.
Engineers estimated that the Thames Barrier could handle possible flooding conditions through 2030 and perhaps through 2070, but due to intensified global warming, that barrier has been activated more often than estimated. Since 1982, operators have shut the Thames Barrier in more than one hundred incidents, with at least 50 percent of those closings happening after the year 2000. If climate change is not slowed and sea levels rise more quickly than projected, the Thames Barrier will become insufficient before engineers envisioned, necessitating plans for the construction of another barrier in the Thames Estuary.
The Italian city of Venice, located adjacent to barrier islands bordering the Adriatic Sea, often experiences flooding. Global warming contributes to rising sea levels, causing excess water to inundate Venice’s lagoon and St. Mark’s Square, which flooded more than one hundred times annually in the twenty-first century compared to six times yearly in the early twentieth century. Extreme floods in 1966 motivated Italian officials to consider more effective flood-control techniques. Concerned climate changes might result in tidal floods destroying Venice, engineers recommended installing movable flood barriers and by 1990 presented a of the modulo sperimentale elettromeccanico (MOSE), also known as the Moses Project.
In 2002, government leaders decided to fund MOSE to build seventy-nine hollow steel gates for placement in the lagoon’s Chioggia, Lido, and Malamocco inlets. Chief engineer Alberto Scotti oversaw construction starting in spring 2003. Because of the project’s complexity, its completion date was shifted from 2010 to 2025. While not fully operational, in 2022, MOSE protected the city from being flooded by a large tide.
The construction of MOSE provoked controversy. Opponents stated the barriers will damage the lagoon environmentally. Continued flooding provoked by global warming emphasized the need for flood control. Projections for sea level increases of a few meters by 2100 caused engineers to recognize the MOSE might need reinforcements to block surges into Venice’s lagoon.
Bibliography
Bijker, Wiebe E. “The Oosterschelde Storm Surge Barrier: A Test Case for Dutch Water Technology, Management, and Politics.” Technology and Culture 43, no. 3 (July, 2002): 569-584.
Donadio, Rachel. “Floodwaters, Worst Since ’86, Begin to Recede in Venice.” The New York Times, December 3, 2008, p. A12.
Harlan, Chico and Stefano Pitrelli. "An Engineering Marvel Just Saved Venice from a Flood. What About When Seas Rise?" The Washington Post, 27 Nov. 2022, www.washingtonpost.com/climate-solutions/2022/11/26/venice-floods-mose-barrier-climate/. Accessed 26 Dec. 2024.
Hoeksema, Robert J. Designed for Dry Feet: Flood Protection and Land Reclamation in the Netherlands. Reston, Va.: American Society of Civil Engineers Press, 2006.
Keahey, John. Venice Against the Sea: A City Besieged. New York: Thomas Dunne Books/St. Martin’s Press, 2002.