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1. The Subsidence Problem
Pages 3-23

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From page 3...
... Subsidence, however, increases the potential for loss of life in flood-prone areas by increasing the depth and size of areas susceptible to flooding. Subsidence is caused by a diverse set of human activities and natural processes, including: mining of coal, metallic ores, limestone, salt, and sulfur; withdrawal of groundwater, petroleum, anal geothermal fluids; dewatering of organic soils; pumping of groundwater from limestone; wetting of dry, low-density deposits, which is known as hydrocompaction; natural sediment compaction; melting of permafrost; liquefaction; and crustal deformation.
From page 4...
... Resource development and land-use practices, particularly underground mining of coal, groun(lwater and petroleum withdrawal, and drainage of organic soils, are the primary causes. The common association of land subsidence win either the exploitation of natural resources or land development practices is an important aspect of subsidence.
From page 5...
... A singular, but spectacular and complex, example was the catastrophic drainage of Lake Peigneur and disappearance of about 27.6 ha of lanct at Jefferson Island, Louisiana, on November 20, 1980 (Figure 2~. The collapse was triggered by the drilling of an oil well inadvertently into an underground salt mine in the Jefferson Island salt dome; damages totaled hundreds of millions of doDars (Autin, 1984~.
From page 6...
... Drainage of organic soils LEGEND Costs ~ <$1 million .$~-10 million $10-100 million .~$100 million FIGURE 1 National distribution of subsidence problems by state. Costs were compiled from published and unpublished sources for the purpose of providing an order-of-magnitude, state-by-state comparison.
From page 8...
... estimates that more than 6,000 collapses have occurred in the eastern United States since about 1950 (Figure 6~. The states with the largest number of active sinkholes include Alabama, Florida, Georgia, Indiana, Missouri, Pennsylvania, and Tennessee.
From page 9...
... Maximum elevation loss from this type of subsidence has been 9 m in the San Joaquin Valley (Figure 7~. Two coastal areas in California and Texas where subsidence caused or threatened inundation and increased flooding potential have suffered the most from this type of subsidence.
From page 10...
... Changes of surface gradients can affect either the design or operation of canals. For example, canals in the State Water and the Central Valley Projects in California and the Central Arizona Project have been affected.
From page 11...
... Mississippi River Delta area of southern Louisiana, where about 3,900 km2 of land is subsiding, at least in part through natural compaction. Estimated average rates of subsidence range from ~ to 11 mm per century (Peniand and others, 1988~.
From page 12...
... Subsidence of 9.0 m occurred from 1925 to 1977. Signs indicate the former elevations of the land surface in 1926 and 1955, respectively.
From page 13...
... For example, subsidence caused by drainage of organic soil and withdrawal of underground fluids is common in many deItaic areas. A well-studied example of this complexity is Venice, Italy, where increases in the incidence of tidal flooding (Figures 12a and by prompted an investigation, which discovered that the mean elevation above sea level had decreased from 130 to Il0 cm since the turn of the century.
From page 14...
... FIGURE 9 Ground ruptures associated with land subsidence caused by groundwater withdrawal.
From page 15...
... The principal areas of organic soil subsidence in the United States are the greater New Orleans, Louisiana, area; the Sacramento-San Joaquin River Delta, California; and parts of the Florida Everglades. Maximum observed subsidence is 6.4 m in the Sacramento-San Joaquin River Delta.
From page 16...
... 16 1838 ~ O jre-openin6/ it/ jrJ1905~ ~ go\' al ~ 1~/ ~ ~~ ~~ \ - ? ~.~ ~ Km 1922 FIGURE 10 Historic maps illustrating natural compaction at Cubits Gap in Mississippi River Delta.
From page 17...
... The costs are dominated by subsidence from underground mining of coal, drainage of organic soils, and withdrawal of underground water and petroleum. These costs consist primarily of direct structural and property losses and depreciation of land values, but they also include business and personal losses that result from periods of repair.
From page 18...
... Frequency of floods, locally known as acqua alla, increased with time as subsidence lowered mean elevation of Venice (Gatto and Carbognin, 1981)
From page 19...
... Failure of the Baldwin HiDs reservoir because of ground rupture caused losses of $15 million. Losses from natural compaction, particularly in the Mississippi River Delta, are difficult to estimate because of the uncertain value of coastal wetlands.
From page 20...
... For example, collapsible soils added more man $2.5 million in mitigation costs to interstate highway construction in Louisiana (arm en and Thomton, 1972~. The incremental increase in the cost and prevention of flood damage caused by organic soil subsidence is difficult to separate from total flood-related costs in areas developed on organic soils.
From page 21...
... The surface property owner affected by subsidence, however, receives none of the benefits, yet bears the extemal costs from the actions of the mine operator. This misallocation of resources is corrected when the mine operator pays all of He social costs, private and external, of the · — mine operation.
From page 22...
... from Land Subsidence Mines Sinkholes Underground fluid withdrawal Natural compaction Hydrocompaction Organic soils TOTAL $ 30 10 35 10 Not available 40 $125 SOURCES: Jones (1977) , Newton (1986)
From page 23...
... Given that subsidence commonly is a phenomenon charactenzed as imposed external cost due to legal conflicts or market failure, what are the barriers to mitigating external costs? At least Tree barriers inhibit the design of appropriate public policy measures.


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