David G. Howell , Earl E. Brabb  and Rafi Ahmad 
1, U.S. Geological Survey, MS/975, Menlo Park, CA 94025
2, Unit for Disaster Studies, Department of Geography and Geology, University of the West Indies, Mona, Kingston 7, Jamaica
Have you ever thought about Jamaica and the San Francisco Bay region as having anything in common? Probably not; how could two places be more different. But are they? When it comes to landslides and associated features their similarities are remarkable. For starters theyre both about the same size. Both are mountainous, the Blue Mountains in Jamaica rising as high as 2254m, quite a bit higher than the 1402m peaks in the Coast Ranges around San Francisco Bay. (Knowing that the latter are even this high surprises many.) Columbus described the rugged terrain on the island of Jamaica to Queen Isabella as a crumpled handkerchief picked up by the middle, Brown, 1907; we can guess that Columbus could have used that same crumpled handkerchief, but with a stone in the middle, to describe San Francisco Bay region.
As far as geologic structure and active tectonics is concerned, both areas are cross cut by major transcurrent fault systems, an expression of their location within seismically active plate boundary zones. Jamaica is a part of the North American-Caribbean plate boundary zone of Neogene left-lateral strike-slip deformation (Mann et al. 1990) and the San Francisco Bay region is a part of the North American-Pacific plate boundary zone of Neogene right-lateral strike-slip deformation ( Atwater, 1970). The transcurrent plate motion of Jamaica is accommodated by the major east-west, throughgoing Enriquillo-Plantain Garden- Duanvale fault zone.
The left-lateral strike-slip tectonics and accompanying northeast-southwest shortening has produced compression and uplift on Jamaica. The geologic structure of eastern Jamaica is defined by east-west, Plantain Garden fault zone with a left-lateral motion, and northwest-southeast, Wagwater and Yallahs-Silver Hill fault zones with a reverse and right-lateral motion (Mann and Burke, 1990). The uplift of Port Royal Mountains, north and east of Kingston reflects block convergence at the restraining bend or a right-step where the east-west Plantain Garden fault zone has intersected the northwest-southeast, Wagwater fault zone (Mann and Burke, 1990). The transcurrent plate motion in San Francisco Bay region is accommodated by the major northwest-southeast throughgoing San Andreas fault system and a small component of east-west compression has produced the downwarped bay bounded by mountains on either side.
The year 1906 was the last major earthquake on the San Andreas ( ) and 1907 was the last major earthquake on the Wagwater-Silver Hill fault system (Isaacs,1985). The port city of San Francisco was destroyed by the former and the port city of Kingston-Port Royal was destroyed by the latter. On a decadel time scale, major tropical hurricanes cross Jamaica triggering numerous landslides, particularly debris flows (Ahmad et al., 1993). On a similar time scale in the San Francisco Bay region so-called pineapple express storm-tracks pass through the area dropping voluminous amounts of rain, triggering 100s to 1000s of debris flows.
The San Francisco Bay region is populated by nearly 8 million people and in Jamaica the population is 2.5 million. Both are encumbered with complex jurisdictional responsibilities. In the San Francisco Bay area, Federal, State, County, City and unincorporated governments vie for control. In Jamaica there are Federal, Parish, and City ordinances as well as a large seemingly independent group of "squatters". For the San Francisco Bay region a digital landslide folio has recently been published (San Francisco Bay landslide mapping team, 1997). For Jamaica, no such digital products are available at the national level. However, landslide susceptibility maps have been prepared for two areas with contrasting land use. The first area is the capital city, Kingston and its environs which has an area of some 554km2 and a population density of approximately 1528 persons/km2. This is a well-developed area with the sub-urban growth increasingly taking place in the hilly terrain of Kingston where rainfall-induced landslides are a recurrent phenomenon. Ahmad and McCalpin (1999) provide detailed landslide inventory, controls on landslides, hazard maps and guidelines for citizens, planners, developers and engineers on how to use landslide susceptibility information in the Kingston area.
The other area is an 11km stretch of land corridor lying inland from the south coast of Jamaica roughly between Kingston in the east and Negril in the west . This section of the island is less developed, however, it has been subject to increasing pressure from new development. Therefore, the Government of Jamaica in collaboration with the Inter-American Development Bank has undertaken " Multisectoral Preinvestment Programme-South Coast Sustainable Development Study(SCDS)" to guide in land use planning and sustainable development. This study is being executed by Sir William Halcrow & Partners with the support of local and international consultants. One of us(RA) was involved in the study of natural hazards for this project and preparation of hazard maps at a scale of 1:50k including landslides(Halcrow,1998). In this area, debris flows triggered by the 12th June 1979 rainfall (some 865 mm of rain was recorded in 12 hours in western Jamaica) caused an extensive damage to public and private property.
Other comparisons and coincidences exist in the two regions but perhaps the most important, germane to the topic at hand, is how landslide information is perceived by decision-makers. The vexing thread that runs through all aspects of landslide information is the difficulty in understanding and communicating the level of risk that individuals and society are willing to take before public and private funds are invested to prevent or reduce loss.
Since the early 1970s, Federal, State and local geologists and engineers have been assembling information about the nature of the landslide hazards in the San Francisco Bay region, but the impact of all this is marginal at best. Over the past twenty years several counties and a number of cities dropped their staffing of a full-time geologist. The U.S. Geological Survey debris-flow warning system has been abandoned and Federal and State regional landslide-mapping programs virtually ceased. Public acknowledgement, individual responses, and government ordinances are not consistent in recognizing any correlation between landslide hazards in hillside environments and prudent land use planning. Clearly, the scientific community has not been able to communicate its message. Effective communication of hazard information is complex. Persistence and credibility are essential in getting across a message that impacts the decisionmaking process. For information to be influential, a sequence of perceptual milestones must be achieved: ensuring first that the message is HEARD, making certain that the message is UNDERSTOOD, then convincing the public to BELIEVE the information, next packaging the information so that individuals can PERSONALIZE the message, and finally, persuading the public to TAKE ACTION. Its hard to tell if we have even gotten past the "heard" hurdle.
On January 26-28, 1999 the Unit for Disasters Studies of the University of the West Indies, Kingston, Jamaica hosted a workshop focused on issues of landslide hazard mitigation and loss-reduction strategies. This workshop was the culmination of the Project Landslide Hazard Mapping for the Kingston Metropolitan Area which is a part of the Kingston Multi-hazard Assessment Project of the Caribbean Disaster Mitigation Project funded by the USAID and administered by the Organization of the American States. Landslide Susceptibility maps for deep and shallow landslides for the Kingston Metropolitan area at 1:50K have been prepared( Ahmad and McCalpin,1999). We decided to take advantage of this occasion in order to document how well landslide information was understood by an array of staff support personnel for decision makers. The questions and responses that follow are anecdotal in nature and limited in number. A more comprehensive survey is surely warranted, but we believe that what is captured here reflects the general attitude about this subject that prevails, not only in Jamaica but seemingly everywhere else in the world.
Fifty people, 40 Jamaicans and five from the U.S. were split into eight groups based on their professional involvement. The general categories included geology, engineering, water and transportation, disaster response, development and urban planning, and environmental management. These groups were asked to comment on several topics about landslide and land-use issues. The topics and questions and an edited summary of their answers are included below:
What is not immediately obvious from this list is the role, if any, that landslides would play in these land-use issues. But what is evident, however, is the array of other problems with which the landslide issue competes.
Perhaps all of these entities do have a role in monitoring landslide activities but it seems to us that a central clearing house is needed. Additionally, the Town and Country Planning Department and the Kingston and St.Andrew Corporation do not posses an in-house expertise to assess the vulnerability of proposed developments to natural hazards. Therefore, they routinely forward applications to other "responsible" agencies for comments. Many of the above agencies may be queried depending on the nature of the proposed development. This process may take a long time before an OK is given to proceed with the development.
The range in answers covers about two orders of magnitude. Estimating costs of landslide damage is always problematic as the direct and indirect costs are rarely collected by a central agency. This condition was emphasized as a seeming fact of life for the 120 countries discussed in the book edited by Brabb and Harrod (1989). From the above range it is understandable why the disparity of opinions exist regarding the severity of the landslide-hazard issue.
All Jamaicans answered YES. The reason for the YES responses include:
Three of the foreign consultants responded NO, without explanation.
Interestingly, unlike California where the population is expanding, the population in Jamaica is reasonably stable. However, the segment of the population that is gaining wealth is moving into hillside settings. Thus, the number of new mountain roads and terraced slopes is increasing, and it is easy to understand why there is a perception that landslide damage would be increasing.
Jamaica has a preliminary 1:250,000 scale map of natural hazards in which information on; the landslide hazard is also included, but the City of Kingston, like the San Francisco Bay, has a far richer data set involving many aspects of the landslide problem. It would also seem evident that at least part of the community of staffers and decision makers have HEARD, UNDERSTOOD AND BELIEVED the information. How much is PERSONALIZED (i.e. factored into the mandate of an agency) and what ACTIONS were taken as a result seem less certain.
Clearly the staffers are cognizant of the kinds of information that are needed. This list of "tools" would certainly help provide a better understanding of the landslide hazard and how to deal with it. But these are costly items, and in the competition for scarce federal dollars these needs are not winning budgetary support. In Jamaica, vehicular congestion and pot-holes in city streets are likely to be more popular issues than unstable slopes. In this regard, the members from the government agency for water and transportation indicated "NONE" for the question above.
These responses are similar but not identical to those for the second question above that asks who is responsible for tracking landslide activity. The absence of a central clearing house surely contributes to the confusion. Confusion is also enhanced by the absence of any clear linkage between agencies that collect landslide damage and those that dispense information about landslides.
This list of maps reflects a sophisticated understanding of the base cartographic information that is needed to effectively deal with the landslide problem. The requested scales are particularly noteworthy. However, it may not always be possible to prepare hazard maps at small scales. There are several reasons for this. To start with, there is no central digital data bank from where digitized topographic information may be purchased. The copyright for all the original topographic maps in Jamaica rests with the Survey Department, Government of Jamaica. In order to digitize the topographic data, Survey Departments permission must be obtained. It is preferable to digitize topographic data using the original mylar separates. Because the original films should not be taken out of the Survey Department, these must be copied within the Survey Department. It may turn out to be a lengthy processes requiring photographic materials and preparing prints. In summary, the practical experience is that it is very costly and time consuming to digitize topographic base maps and prepare a DEM. While the user agencies would like to have the data and the scales they need to facilitate their work, they may not be in a position to share the costs of map preparation.
Yes, by all participants
However, there was concern voiced by many that low-income people probably could not afford insurance. A number of the participants suggested that the central government should provide funding for such an insurance programme; yet, to have a long-term positive effect, such a government program must not encourage or reward bad planning by reimbursing with public funds loss-damages in areas known to have a high landslide susceptibility. This is a lesson that has been learned with the U.S. National Flood Insurance Program.
By interrogating a cross section of staffers and decision makers in Jamaica a number of universal truths may have surfaced. Clearly, landslides are affecting the functions of many different agencies, housing: transportation, water quality, safety, and forest management to name the most obvious. Nonetheless, in spite of this broad interest and the array of scientific information that already existin Jamaica, in San Francisco Bay region, and many other placesland-use decisions are often made absent the benefit of landslide information. Perhaps three factors are contributing to this: (1) no single agency is recognized as the principal authority on landslide hazard issues, (2) the landslide information that is available is dispersed across a morass of agencies and it is often packaged in cartographic scales that are too regional (too broad) to be useful for single-site evaluation, and (3) the events that trigger significant landslide events are too infrequent to capture and sustain the interest of the public and responsible government agencies.
The squeak from landslide wheels is drummed out by the din of other societal woes such as crime, traffic, education, and health. Thus, the challenge is clear. We must demonstrate the real savings in both public and private funds that follow prudent land-use planning and mitigation measures. We must communicate this message all the way through the decision-making process. And we must provide the information that is being requested, e.g. large-scale hazard maps. To communicate and implement our understanding of landslides will necessarily involve a host of disciplines, in both government agencies and in the private sector. There are many niches to fill and an understanding of our various roles and responsibilities is critical if we are to be successful. Perhaps a good objective would be the formulation of national landslide insurance programs (Olshansky and Rogers, 1987). These could provide financial safety nets that in turn encourage wise land-use investments, but not reimbursements for reckless development in highly vulnerable areas. To formulate an effective program, however, the geologic and engineering communities will need to assemble credible Earth-science maps and data that characterize in detail the vulnerabilities of a whole variety of hillside environments.
Lessons learned from the Kingston study, reported here, are relevant to other sustainable development project involving use of the landslide hazard information in development planning, e.g. the South Coast Sustainable Development Study in Jamaica . Our conclusions and approach may benefit many such programmes worldwide.
Ahmad, R., Scatena, F.N. and Gupta, A., 1993, Morphology and sedimentation in Caribbean montane streams: examples from Jamaica and Puerto Rico, Sedimentary Geology, v.85, p.157-169.
Ahmad, R., and McCalpin, J.P., in press, Landslide susceptibility maps for Kingston Metropolitan Area, Jamaica, Publication No.5, Unit for Disaster Studies, University of the West Indies, Mona, Kingston 7, Jamaica, 1999.
Atwater, T., 1970, Implication of plate tectonics for the Cenozoic tectonic evolution of western North America: Geol. Soc. America Bull., v. 81, p. 3513- 3536.
Brabb, E.E. and Harrod, B.L., eds., 1989, Landslides: Extent and economic significance, in International Geological Congress, 28th, Washington, 1989, Proceedings: Rotterdam, Balkema, 349 p.
Halcrow, 1998, Technical Report 4 Geology and Natural Hazards, October 1998, Multisectoral Preinvestment Programme South Coast Sustainable Development Study, Prepared for Government of Jamaica by Sir William Halcrow and Partners Ltd., 115p.and Appendices A1 to C4.
Mann, P. and Burke, K., 1990, Transverse intra-arc rifting: Paleogene Wagwater Belt, Jamaica, Marine and Petroleum Geology, v.7, p. 410-427.
Mann,P., Schubert, C. and Burke, K., 1990, Review of Caribbean neotectonics, In Dengo, G.and Case, J.E.(eds), The Caribbean Region, chapter 12, v.H, The Geology of North America, Geological Society of America, Boulder, Colorado,p. 307-338.
Olshansky, R. B. and Rogers, J.D., 1997, Unstable Ground: Landslide Policy in the United States; Ecology Law Quarterly, v.13, no.4, p. 939-1006.
San Francisco Bay Landslide Mapping Team, 1997, San Francisco Bay Region, California, Landslide Folio: U.S. Geological survey open-file 97-745 A-F
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