kChapter 2 ROBERT L. SCHUSTER SOCIOECONOMIC SIGNIFICANCE OF LANDSLIDES 1. INTRODUCTION wildlife), landslides destroy or damage residential and industrial developments as well as agricultural andslides have been recorded for several and forest lands and negatively affect water qual- L centuries in Asia and Europe. The oldest ity in rivers and streams. landslides on record occurred in Honan Province Landslides are responsible for considerably in central China in 1767 B.C., when earthquake- greater socioeconomic losses than is generally rec- triggered landslides dammed the Yi and Lo rivers ognized; they represent a significant element of (Xue-Cai and An-ning 1986). many major multiple-hazard disasters. Much land- The following note by Marinatos may well refer slide damage is not documented because it is con- to a catastrophic landslide resulting in serious so- sidered to be a result of the triggering process (i.e., cial and economic losses: part of a multiple hazard) and thus is included by the news media in reports of earthquakes, floods, In the year 3 73/2 B.C., during a disastrous win- volcanic eruptions, or typhoons, even though the ter night, a strange thing happened in central cost of damage from landslides may exceed all Greece. Helicé, a great and prosperous town other costs from the overall multiple-hazard disas- on the north coast of the Peloponnesus, was ter. For example, it was not generally recognized engulfed by the waves after being leveled by a by the media that most of the losses due to the great earthquake. Not a single soul survived. 1964 Alaska earthquake resulted from ground fail- (Marinatos 1960) ure rather than from shaking of structures. Government agencies and those who formulate Research by Marinatos indicated that Helice prob- policy need to develop a better understanding of ably was engulfed as the ground slipped toward the the socioeconomic significance of landslides. That sea a distance of about 1 km. Seed (1968) con- knowledge will allow officials at all levels of gov- cluded that this was a major landslide, resulting ernment to make rational decisions on allocation from soil liquefaction caused by the earthquake. of funds needed for landslide research; for avoid- Slope failures have caused untold numbers of ance, prevention, control, and warning; and for casualties and huge economic losses. In many postfailure repair and reconstruction. countries, economic losses due to landslides are great and apparently are growing as development 2.FUTURE LANDSLIDE ACTIVITY expands into unstable hillside areas under the pressures of expanding populations. In addition to In spite of improvements in recognition, predic- killing people and animals (both livestock and tion, mitigative measures, and warning systems, 12 Socioeconomic Significance of Landslides 13 worldwide landslide activity is increasing; this Removal of forest cover increases flooding, ero- trend is expected to continue in the 21st century. sion, and landslide activity. Deforestation, which The factors causing this expected augmented ac- is expected to continue unimpeded into the 21st tivity are century, is causing serious landslide problems in many of these countries, Nepal being the best- Increased urbanization and development in documented example. According to the World landslide-prone areas, Resources Institute (Facts on File Yearbook 1990), Continued deforestation of landslide-prone approximately 15 to 20 million ha of tropical for- areas, and est is currently being destroyed annually, an area Increased regional precipitation caused by the size of the state of Washington. changing climate patterns. 2.3 Increased Regional Precipitation 2.1 Increased Urbanization and Development For a period of about 3 years in the early 1980s, El Niño caused regional weather changes in western Population pressures are increasing in most of the North America that resulted in much heavier- world today and have resulted in rapid urbaniza- than-normal precipitation in mountainous areas. tion and development. For example, in the One of the results was a tremendous increase in United States the land areas of the 142 cities with landslide activity in California, Colorado, Nevada, populations greater than 100,000 increased by 19 Oregon, Utah, and Washington. Climatologists do percent in the 15-year period from 1970 to 1985. not know what to expect from future El Niños Legget (1973) estimated that by the year 2000, except that these climatic perturbations will also 360 000 km2 in the 48 conterminous United States will have been paved or built upon. This is change climate patterns, certainly increasing pre- an areA about the size of the state of Montana. As cipitation in some areas of the world and thus caus- a result of these population pressures, human ing landslide activity. activities have disturbed large volumes of geologic Scientists do not know what to expect from the materials in housing development and in con- much-publicized greenhouse effect either. Will it struction of industrial structures, transpdrtation cause an overall increase in temperature and routes and facilities, mines and quarries, dams and decrease in precipitation (as occurred in central reservoirs, and communications systems. Because North America in the late 1980s) or will it disrupt of the huge extent of these activities, they increas- climate patterns, resulting in drought in some ingly have expanded into landslide-prone areas; areas and increased precipitation in others (as thus, these developments have been a major factor occurred in western North America at the same in the recent increase in damaging slope failures. time)? If areas that are prone to landsliding are In other countries, particularly developing coun- subjected to greater-than-normal precipitation, tries, this pattern is being repeated, but with even they are apt to experience increased landslide more serious consequences. As development occurs, activity. more and more of it is on hillside slopes that are susceptible to landsliding. All predictions are that worldwide slope distress due to urbanization and de- 3. ECONOMIC LOSSES CAUSED BY velopment will accelerate in the 21st century. LANDSLIDES Population pressures are also causing increased landslide losses in other ways. An obvious example In this discussion of the expense of landslides at is the necessary construction of transportation fa- national and local levels, the costs are given in cilities required by expanding populations. In land- U.S. dollars for the time at which they were slide-prone areas, these facilities are often at risk. originally determined, except where noted. In addition, the original values adjusted to 1990 U.S. dollars are presented in parentheses; the 2.2 Continued Deforestation adjustments were made on the basis of yearly In many of the developing nations of the world, cost-of-living indexes for the United States forests are being destroyed at ever-increasing rates. (Council of Economic Advisers 1991). 14 Landslides: Investigation and Mitigation 3.1 Categories of Damage Costs damage to land or facilities or interruption of transportation systems; There are significant advantages to the ability of Reduced real estate values in areas threatened government officials, land use planners, and others by landslides; to distinguish between direct and indirect land- Loss of tax revenues on properties devalued as slide costs and to determine whether these costs the result of landslides; affect public or private entities. Measures to prevent or mitigate additional landslide damage; 3.1.1 Direct Versus Indirect Costs Adverse effects on water quality in streams and irrigation facilities outside the landslide; Landslide costs include both direct and indirect Loss of human or animal productivity because losses that affect public and private properties. Direct costs are the repair, replacement, or main- of injury, death, or psychological trauma; and tenance resulting from damage to property or in- Secondary physical effects, such as landslide- stallations within the boundaries of the responsible caused flooding, for which losses are both direct landslides or from landslide-caused flooding. An and indirect. outstanding example of direct costs resulting from a single major landslide is the $200 million ($260 Indirect costs may exceed direct costs; unfortu- million) loss due to the 1983 Thistle, Utah, land- nately, however, most indirect costs are difficult to slide (University of Utah 1984). This 21- evaluate and thus are often ignored or, when esti- million-rn3 debris slide (Figure 2-1) severed major mated, are too conservative. transportation arteries, and the lake it impounded inundated the town of Thistle and railroad switch- 3.1.2 Public Versus Private Costs ing yards. All other costs of landslides are indirect. Of possibly greater importance than whether costs Examples of indirect costs are are directly or indirectly attributable to a landslide is attribution of the costs on the basis of who is ac- 1. Loss of industrial, agricultural, and forest pro- tually faced with the losses. On this basis, land- ductivity and tourist revenues as a result of slide losses can he separated into costs to public FIGURE 2-1 Aerial view in September 1983 of April 1983 Thistle debris slide, Utah, showing Thistle Lake, which was impounded by the landslide; realignment of Denver and Rio Grande Western Railroad in lower center; and large cut for rerouting US-6/50 in extreme lower left. Socioeconomic Significance of Landslides 15 and private entities (Fleming and Taylor 1980). obtain. In the public sector, accounting for land- The possibility of a major landslide that could de- slide costs is often lost within general mainte- stroy port facilities and create a wave that might nance operations; this seems to be particularly inundate downtown Kodiak, Alaska, is an exam- common for transportation agencies. To separate pie of a landslide threat during the 1970s and out landslide costs is in itself a costly and compli- 1980s that is alleged to have caused indirect costs cated operation. In the private sector, the costs relating to planning for expansion of the port area incurred by natural hazards are often downplayed (Schuster and Fleming 1988).