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Cite several reasons why Venice, Italy faces a continual threat of flooding. What steps are being attempted to mitigate the process?

Cite several reasons why Venice, Italy faces a continual threat of flooding. What steps are being attempted to mitigate the process?

Applications and Investigations in Earth Science (9th Edition)
Applications and Investigations in Earth Science (9th Edition)
9th Edition
ISBN:9780134746241
Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
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Cite several reasons why Venice, Italy faces a continual threat of flooding. What steps are being attempted to mitigate the process? (See Essay 7.2)

### Venice's Sinking Dilemma and the Mose Project: A Study Venice has been slowly sinking due to its own weight for centuries. This problem was exacerbated from the 1930s to 1970s by the withdrawal of large quantities of groundwater for industrial use. Groundwater occupies the tiny pore spaces in sediment and, as the water is pumped out, the sediment compacts and the ground subsides. Land subsidence is also occurring because of the oxidation of organic-rich soils in fertile farmland that had been reclaimed from marshland at the southern end of the Venice lagoon. A drainage system that keeps the soil relatively dry promotes oxidation and, consequently, loss of soil mass. The rate of subsidence has decreased, but it is still about 2 mm (0.07 in.) per yr, and the Venice region is also tilting eastward by about 1–2 mm (0.04–0.07 in.) per yr, meaning that the central lagoon area that includes the city of Venice is higher than the northern and southern extremities of the Venice lagoon area. Although the practice of groundwater pumping has ended, the current subsidence is partially due to continued compaction of sediments underneath Venice. Another contributing factor is plate tectonics, as the Adriatic Plate, upon which sits Venice, subducts under the Apennines Mountains to the south, which stretch northwest-to-southeast across central Italy. Complicating the situation is that the sea level in the Venetian lagoon is rising at about 2 mm (0.07 in.) per yr. Scientists calculate that at the current subsidence rate, in 20 years the land will sink 80 mm (3.2 in.) relative to the sea. **Acqua alta** or high water refers to the flooding in Venice caused by the very high tides that intermittently occur in the Northern Adriatic Sea. These tidal events are categorized as intense, very intense, and exceptionally high. Over the past 95 years, 17 exceptional high tidal events have inundated Venice, while smaller floods have become much more frequent. Portions of Venice, including the historic Piazza San Marco, are flooded about 100 days per year. More than a century ago, the same area flooded only about 7 days per year. Flooding forces businesses to close and inconveniences residents and tourists alike. More significantly, the saltwater corrodes the brick underpinnings of historic buildings along the Grand Canal and elsewhere in the
Transcribed Image Text:### Venice's Sinking Dilemma and the Mose Project: A Study Venice has been slowly sinking due to its own weight for centuries. This problem was exacerbated from the 1930s to 1970s by the withdrawal of large quantities of groundwater for industrial use. Groundwater occupies the tiny pore spaces in sediment and, as the water is pumped out, the sediment compacts and the ground subsides. Land subsidence is also occurring because of the oxidation of organic-rich soils in fertile farmland that had been reclaimed from marshland at the southern end of the Venice lagoon. A drainage system that keeps the soil relatively dry promotes oxidation and, consequently, loss of soil mass. The rate of subsidence has decreased, but it is still about 2 mm (0.07 in.) per yr, and the Venice region is also tilting eastward by about 1–2 mm (0.04–0.07 in.) per yr, meaning that the central lagoon area that includes the city of Venice is higher than the northern and southern extremities of the Venice lagoon area. Although the practice of groundwater pumping has ended, the current subsidence is partially due to continued compaction of sediments underneath Venice. Another contributing factor is plate tectonics, as the Adriatic Plate, upon which sits Venice, subducts under the Apennines Mountains to the south, which stretch northwest-to-southeast across central Italy. Complicating the situation is that the sea level in the Venetian lagoon is rising at about 2 mm (0.07 in.) per yr. Scientists calculate that at the current subsidence rate, in 20 years the land will sink 80 mm (3.2 in.) relative to the sea. **Acqua alta** or high water refers to the flooding in Venice caused by the very high tides that intermittently occur in the Northern Adriatic Sea. These tidal events are categorized as intense, very intense, and exceptionally high. Over the past 95 years, 17 exceptional high tidal events have inundated Venice, while smaller floods have become much more frequent. Portions of Venice, including the historic Piazza San Marco, are flooded about 100 days per year. More than a century ago, the same area flooded only about 7 days per year. Flooding forces businesses to close and inconveniences residents and tourists alike. More significantly, the saltwater corrodes the brick underpinnings of historic buildings along the Grand Canal and elsewhere in the
**ESSAY 7.2: Venice, Italy, and the Encroaching Sea** Many of the world’s most populous cities are located along the coast. These communities are vulnerable to storm-generated and enhanced tidal-related flooding, especially as mean sea level (msl) rises in response to global climate change. The impact of storm surge on a major U.S. city was starkly evidenced by the catastrophic flooding caused by Hurricane Katrina in 2005. Metropolitan New Orleans is especially vulnerable as it occupies a bowl between the Mississippi River and Lake Pontchartrain. Much of the bowl, home to 1.25 million residents and businesses, is 1.8 m (6 ft.) below sea level. The people of New Orleans depend on earthen levees and concrete floodwalls to keep the water out, and pumps to remove accumulating waters, including those from flooding. According to the U.S. Army Corps of Engineers, the levees were designed to withstand a hurricane no stronger than a category 3. The combination of Katrina’s strong winds, storm surge, and heavy rainfall caused numerous breaches in the New Orleans levee system and the pumps failed. Up to 80% of the city was flooded to depths that in many places reached 6 m (20 ft.). Along with Katrina (2005), recent major flooding has occurred in coastal cities worldwide. Population in coastal zones and very large cities is projected to increase 25% by mid-century. Sea-level rise may exacerbate severe flooding events. The vulnerability of major cities worldwide is not a new problem. The city of Venice in northern Italy has been battling this problem for centuries. Venice is situated at the head of the Adriatic Sea on a cluster of 120 salt-marsh islands in a large coastal lagoon, one of the most important wetlands in the Mediterranean Basin [Essay 7.2 Figure 1]. Some 200,000 birds use the lagoon as a winter migration destination and breeding area. Bridges connect some of the islands and a causeway and ferries link Venice to the mainland. A long narrow barrier island separates the lagoon from the sea (Gulf of Venice). At one time, the sea and the lagoon protected the city from foreign invaders. Today, the encroaching sea threatens Venice’s art and architectural treasures, and perhaps the city’s continued existence. [Essay 7.2 Figure 1] The satellite image shown here illustrates Venice, its surrounding islands, and the coastal lagoon. The color
Transcribed Image Text:**ESSAY 7.2: Venice, Italy, and the Encroaching Sea** Many of the world’s most populous cities are located along the coast. These communities are vulnerable to storm-generated and enhanced tidal-related flooding, especially as mean sea level (msl) rises in response to global climate change. The impact of storm surge on a major U.S. city was starkly evidenced by the catastrophic flooding caused by Hurricane Katrina in 2005. Metropolitan New Orleans is especially vulnerable as it occupies a bowl between the Mississippi River and Lake Pontchartrain. Much of the bowl, home to 1.25 million residents and businesses, is 1.8 m (6 ft.) below sea level. The people of New Orleans depend on earthen levees and concrete floodwalls to keep the water out, and pumps to remove accumulating waters, including those from flooding. According to the U.S. Army Corps of Engineers, the levees were designed to withstand a hurricane no stronger than a category 3. The combination of Katrina’s strong winds, storm surge, and heavy rainfall caused numerous breaches in the New Orleans levee system and the pumps failed. Up to 80% of the city was flooded to depths that in many places reached 6 m (20 ft.). Along with Katrina (2005), recent major flooding has occurred in coastal cities worldwide. Population in coastal zones and very large cities is projected to increase 25% by mid-century. Sea-level rise may exacerbate severe flooding events. The vulnerability of major cities worldwide is not a new problem. The city of Venice in northern Italy has been battling this problem for centuries. Venice is situated at the head of the Adriatic Sea on a cluster of 120 salt-marsh islands in a large coastal lagoon, one of the most important wetlands in the Mediterranean Basin [Essay 7.2 Figure 1]. Some 200,000 birds use the lagoon as a winter migration destination and breeding area. Bridges connect some of the islands and a causeway and ferries link Venice to the mainland. A long narrow barrier island separates the lagoon from the sea (Gulf of Venice). At one time, the sea and the lagoon protected the city from foreign invaders. Today, the encroaching sea threatens Venice’s art and architectural treasures, and perhaps the city’s continued existence. [Essay 7.2 Figure 1] The satellite image shown here illustrates Venice, its surrounding islands, and the coastal lagoon. The color
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