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3 Itf102tfs18 Land reclamation makes otherise inaccessible areas available for human use. Samps, deserts, and submerged coastal lands are naturally inaccessible surface mines, aste-disposal sites, and municipal landfills are aste areas created by human activity. The land reclaimed from such areas has been used for agricultural and forest crops, recreation, ildlife, and industrial or residential development.tpar tpar SItbtf102tfs18 RECLAMATION OF NATURALLY INACCESSIBLE AREAStpar tpar SItf102tfs18 Naturally inaccessible areas are frequently the result of moisture extremes. et areas must be either drained or land-filled. Drainage see drainage systems is accomplished in several ays by building a system of channels, by laying drainage pipes, and by pumping. In many cases embankments must be constructed to keep ater out of the reclaimed areas. landfill operations require large quantities of suitable fill material such as sand, hich is often obtained by dredging adjacent areas. ater is supplied to arid areas either by pumping it from underground sources or by transporting it through an irrigation system.tpar tpar Reclamation of etlands has significantly enhanced the ell-being of several nations. The Netherlands is an outstanding example. Over a period of centuries the amount of arable land has been significantly increased by the construction of dikes, enclosing portions of the shallo coastal aters, hich are then drained off. The Zuider Zee project, the first phase of hich as a 29-km 18-mi dike completed in 1932, has created nearly 200,000 ha 500,000 acres of polders, hich is land reclaimed from the sea. Because much of this land is belo sea level, continuous pumping is required to maintain the desired ater-table level.tpar tpar Considerable areas in salt marshes have also been reclaimed in eastern England by constructing embankments that separate the marshes from the sea and draining the marshes both ith ditches inside the embankments and through tidal sluices. Because the marshes are above sea level, pumping is not needed. Land reclaimed from the sea has such a high salt level that only salt-tolerant vegetation can be planted during the first fe years. Hoever, after several years, rain leaches out most of the sodium ions and soil conditions improve.tpar tpar An example of large-scale reclamation of freshater marshes is the drainage in the 1930s of the Pontine Marshes of Italy, a 75,000-ha 195,000-acre region of dunes and marshes about 70 km 45 mi southest of Rome. The project not only opened ne land for settlement and agriculture but also helped control malaria, a product of the marshes.tpar tpar Reclamation of etlands has been less actively pursued in the United States, because such areas are highly productive habitats for fish, shellfish, birds, and ildlife. Reclamation of arid lands, hoever, has been a major goal of the U.S. Bureau of Reclamation. The Loer Colorado River Project has transformed desert areas, such as the Imperial Valley of California, into some of the most productive cropland in the orld.tpar tpar The Dutch experience also points a arning, hoever. Although Dutch farmers have rested some of the orlds highest yields from their reclaimed lands, they have done so at considerable expense. The annual cost of drainage and dike repairs exceeds 400 million runoff from fertilizers and pesticides adds to the burden of ater pollution the constant pumping has compressed polder soils, causing them to sink hile, at the same time, it is feared that sea levels may be rising. In consequence, in 1993 the Netherlands government announced plans to reverse the reclamation process, returning over 240,000 ha 600,000 acres to marsh, lake, and forest.tpar tpar SItbtf102tfs18 RECLAMATION OF ARTIFICIALLY CREATED ASTE AREAStpar tpar SItf102tfs18 The major problems associated ith aste areas that are the result of human activitytd1industry, mining, and aste disposaltd1are slope instability, chemical leachates, and soil nutrient deficiencies. Such aste areas occupy only a small fraction of the land area, but they are frequently concentrated in highly populated regions and, in addition to their ugliness, often cause air and ater pollution over idespread areas. In such cases the need for reclamation is particularly pressing but hen it is accomplished, it results in healthier environments as ell as useful land. Slope instability can be reduced by reshaping the aste areas into landforms ith gentler slopes that ill conform ith the surrounding landscape features. Erosion is prevented through ater-control measures and the establishment of a vegetative cover.tpar tpar The Aberfan disaster in ales in 1966td1in hich 170 people, mostly schoolchildren, ere killed hen a coal-refuse bank collapsedtd1resulted in one of the largest reclamation projects of derelict land. The piles of black astes that ere formerly so common in many of the urban areas of England and ales have been transformed into landscaped parks and preserves. Because of their proximity to heavily populated areas, costs have been high, but large numbers of people have benefited from the vastly improved environment.tpar tpar Many disused mine-aste piles dot the landscapes of the older coal-mining regions of the United States, particularly in the East. Although most cause serious environmental problems, fe have been reclaimed.tpar tpar SItbtf102tfs18 Reclamation of Surface-Mined Landtpar tpar SItf102tfs18 Of much greater magnitude in terms of the amount of land involved are the scars left by surface-mining operations, especially here coal has been mined. Federal and state las no require the reclamation of land disturbed by strip-mining operations, and a concerted effort is underay to reclaim land disturbed in past operations. Most commonly mine operators are required to restore the land to a use at least as good as that hich existed prior to mining. This restoration may involve stockpiling the upper soil layers, segregating and burying potentially toxic material, reshaping the piles to approximately the original contour, respreading the soil, and establishing a vegetative cover. Such reclamation is most efficiently done as part of the mining operation. Reclamation of old abandoned surface mines is more difficult and more costly.tpar tpar Reclamation of surface-mined areas in the estern United States and Canada is even more difficult because of the arid climate and, in some cases, high elevations. Nevertheless, surface mining ill probably expand rapidly there in the next fe decades, not only for coal but also for oil shale and oil sands.tpar tpar SItbtf102tfs18 Reclamation of Chemically Polluted Landtpar tpar SItf102tfs18 Methods used in alleviating problems of chemical pollution vary, depending upon the nature of the chemicals involved. High concentrations of soluble salts can be reduced by leaching the salts from the surface layers of the soil ith ater. Acidity can be lessened by ap...
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