Commentary on Characteristics and Implementation of a National Landslide Hazards Mitigation Strategy

Landslides are widely distributed geographically, and pose differing types of hazards depending on geologic setting and terrain type. Landslide problems involve a wide range of issues that are of concern to government agencies at all levels—federal, state, and local. Addressing landslide hazard mitigation issues will require a substantial outreach effort to achieve effective integration and coordination amongst these agencies, with their differing responsibilities and capabilities. The diversity of landslide problems, and the breadth of the needed elements of a national landslide hazard reduction program, can be illustrated by examples:

  • Debris flows triggered by extreme rainfall events have had devastating effects in mountainous regions of the United States. Improved understanding of the initiation and propagation of these flow events is needed in order to reduce the hazard they pose.

  • Rock falls pose severe hazards, particularly along transportation corridors, in many mountainous states. The science related to rock falls is relatively well understood, but improvement is needed in standards of risk management in many areas, and this can be achieved by encouraging more widespread adoption of established techniques through technology transfer.

  • Bedrock slides occur in many locations throughout the United States. Although bedrock slides can be mapped readily if the needed resources are available, they nevertheless continue to cause extensive economic losses due to ineffective regulatory controls on development in slide-prone areas.

Prioritizing Landslide Hazard Mitigation Activities

In general, improved risk assessment is needed for all types of landslide hazards, as are advances in methods of cost-effective mitigation that might include hazard insurance and other financial instruments. More specifically, the establishment of priorities should take existing knowledge and the potential for cost-effective results into consideration. A matrix illustrating some of the major activities that would be embraced in an effective national strategy to address the diversity of landslide hazard problems is shown below, evaluating five typical landslide types against five activities that could be applied to address landslide problems:

  • Adequate understanding of landslide triggering and landslide movement mechanisms are a fundamental requirement for other activities, and improvement of the science base is an essential first step to fill gaps in the current understanding.

  • Technology integration and transfer is important for both dissemination of scientific understanding of the hazard and the identification of appropriate mitigation methods.

  • Mapping provides the fundamental database for identification and delineation of landslide hazards.



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Assessment of Proposed Partnerships to Implement a National Landslide Hazards Mitigation Strategy: Interim Report Commentary on Characteristics and Implementation of a National Landslide Hazards Mitigation Strategy Landslides are widely distributed geographically, and pose differing types of hazards depending on geologic setting and terrain type. Landslide problems involve a wide range of issues that are of concern to government agencies at all levels—federal, state, and local. Addressing landslide hazard mitigation issues will require a substantial outreach effort to achieve effective integration and coordination amongst these agencies, with their differing responsibilities and capabilities. The diversity of landslide problems, and the breadth of the needed elements of a national landslide hazard reduction program, can be illustrated by examples: Debris flows triggered by extreme rainfall events have had devastating effects in mountainous regions of the United States. Improved understanding of the initiation and propagation of these flow events is needed in order to reduce the hazard they pose. Rock falls pose severe hazards, particularly along transportation corridors, in many mountainous states. The science related to rock falls is relatively well understood, but improvement is needed in standards of risk management in many areas, and this can be achieved by encouraging more widespread adoption of established techniques through technology transfer. Bedrock slides occur in many locations throughout the United States. Although bedrock slides can be mapped readily if the needed resources are available, they nevertheless continue to cause extensive economic losses due to ineffective regulatory controls on development in slide-prone areas. Prioritizing Landslide Hazard Mitigation Activities In general, improved risk assessment is needed for all types of landslide hazards, as are advances in methods of cost-effective mitigation that might include hazard insurance and other financial instruments. More specifically, the establishment of priorities should take existing knowledge and the potential for cost-effective results into consideration. A matrix illustrating some of the major activities that would be embraced in an effective national strategy to address the diversity of landslide hazard problems is shown below, evaluating five typical landslide types against five activities that could be applied to address landslide problems: Adequate understanding of landslide triggering and landslide movement mechanisms are a fundamental requirement for other activities, and improvement of the science base is an essential first step to fill gaps in the current understanding. Technology integration and transfer is important for both dissemination of scientific understanding of the hazard and the identification of appropriate mitigation methods. Mapping provides the fundamental database for identification and delineation of landslide hazards.

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Assessment of Proposed Partnerships to Implement a National Landslide Hazards Mitigation Strategy: Interim Report Risk assessment integrates the many factors relating to slide occurrence and consequence. It can be applied at various levels, ranging from qualitative to quantitative. Mitigation takes many forms, with land use regulation being the most important. Other mitigation activities include stabilization through engineering activities and construction of diversion works. Shaded boxes indicate activities with the highest payoff potential. Debris Flow Investment in basic research to improve understanding of debris flow initiation and movement has a high payoff potential, and should precede additional efforts in technology integration and transfer. The basic scientific advances will also contribute to improved mapping, which is a priority requirement. In addition, clarification of magnitude-frequency-runout characteristics can be anticipated, and these are important for risk assessment and mitigation (including regulation). Improved mitigation methods and the establishment of appropriate risk assessment techniques are needed. Rock Fall Rock fall processes are relatively simple and reasonably well understood. The FHWA (Federal Highway Administration) and some state highway departments have made substantial progress in technology integration and transfer. It appears that widespread dissemination of this information would encourage implementation and have a high payoff potential. At the same time, improved mitigation methods and the establishment of appropriate risk assessment techniques are needed. Bedrock Slides There is reasonable understanding of the mechanics of bedrock slide initiation, although additional case histories would add significantly to the body of knowledge. Post-failure deformations are less understood. Bedrock slides can be identified with current technology and there is high payoff potential associated with mapping them in areas of high risk, in order to assist regulation. Improved mitigation methods and the establishment of appropriate risk assessment techniques are needed.

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Assessment of Proposed Partnerships to Implement a National Landslide Hazards Mitigation Strategy: Interim Report Liquefaction Flow This refers to seismically-induced ground failure. The basic science of this process has received considerable attention in recent years, and liquefaction susceptibility criteria have been established and tested in the field. A high payoff potential can be expected from mapping this hazard. As above, improved mitigation methods and the establishment of appropriate risk assessment techniques are needed. Soft Clay Slides Geotechnical engineers have devoted substantial effort to understanding the mechanics of soft clays, and as a consequence the initiation and movement of landslides in these deposits are the best understood of all landslide types. Mapping is straight-forward. Improved mitigation methods and the establishment of appropriate risk assessment techniques are needed. The development of a national strategy to reduce landslide hazards does not mean that all geographic areas need mapping, that all areas mapped need to be mapped at the same level of detail, or that all research topics need to be pursued. Rather, the strategy should be selective in its approach, and devised so as to concentrate efforts on geographic areas and topics for which mapping and research will have the greatest payoffs in reducing vulnerability and losses. One fundamental question that must be answered in a national strategy is the balance between research and mapping. The strategy should identify those topics most in need of research that have the highest probability of being applied to reduce the risk from landslides. The strategy should also call for mapping areas where hazards are high and the risks to infrastructure and population are great. National Strategy Participants and Roles The overall effort needed to mitigate the effects of landslides is extremely large and of necessity requires the cooperation of federal, state and local governments as well as the private sector (NRC, 2001). The different parties should have their individual interests expressed in the strategy so that a clear picture of the total needs of the nation is obtained. It is critical to arrive at a division of responsibilities for implementing the strategy. As a national program, this translates into defining the federal role in the allocation of funds in order to achieve the overall objectives of the program. An appropriate federal role would address the following topics: funding or undertaking critical research that would not otherwise be undertaken; stimulating and coordinating federal agencies in their missions; providing financial and technical assistance to state governments for mapping projects or assisting in mapping; and assisting selected local governments to develop innovative landslide risk-reduction demonstration programs. In the research area, funding and collaboration among the government labs and with universities should be a part of the strategy. The success of the strategy will be no greater than the quality of the earth science, engineering, and social science components of the program. The best and most recent advances in these fields need to be employed. This can only be achieved when there is a full and open flow of information between participants, requiring a coordinated system for information storage and communication. Public and private decisions with respect to land use and development must of necessity take into account the existing landslide hazard and potential risk to development, as well as the potential for landslide risk to be exacerbated by human activities. Risk is inherent in virtually all decisions made by society, whether consciously stated and understood or not. Recent advances in risk analysis that

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Assessment of Proposed Partnerships to Implement a National Landslide Hazards Mitigation Strategy: Interim Report incorporate an understanding of the hazard, the range of risks, and the uncertainties associated with both need to be a central part of a national landslide strategy in order to guide appropriate decisions by public and private sectors. Risk analysis tools have value at all levels of government as well as in the private sector. Provisions should be included in a national strategy to support the development and application of appropriate risk analysis techniques for the range of landslide situations. In most cases, land use and development decisions that affect the vast urban development occurring throughout the country are made locally, normally at city or county level. Most of the population will have the level of risk that they may be exposed to established by decisions of city councils and boards of supervisors, or their equivalents. These officials do not and cannot be expected to have a sophisticated knowledge of the risks of landslides. The strategy must therefore include the information, tools, and training that will help ensure enlightened local decisions that adequately reflect the desires of relevant stakeholders In many instances, informed local decisions can only be made when state levels of government encourage and require local actions that seek to reduce landslide risk. Responses to landslide and other hazards are usually conditioned by the financial implications of decisions. The financing industry can determine what properties to insure if they have reliable and useable information concerning landslide hazards and risks. The insurance industry can also potentially play a critical role if the risks from landslides are known and conveyed. Both the lending and insurance industries have only been marginally involved in the landslide hazard area, but the potential for these sectors to have a more significant role in addressing landslide risks should be explored. Implementation of a National Strategy In order to implement a national strategy, the goals of the program need to be clearly stated and justified. They also need to be translated into specific targets against which progress can be measured. This should serve not only to measure the degree of success, as assessed by the usefulness and effectiveness of the strategy, but also would provide a basis for course corrections as needed. The implementation plan for a national landslide hazards mitigation strategy must recognize the capabilities of ongoing programs within the federal, state, university, and local structures. A primary objective must be to develop a cohesive program from these individual distributed components, with specific assignments, funding, and scheduling. The lead federal agency must accept this responsibility unequivocally, and provide the administrative structure, guidance, and funding. Funding for each sector or unit of work can be established using existing interagency procedures to establish formalized cooperative programs between federal, state, and local entities (e.g. cooperative water resources agreements and mapping programs between the USGS and state geological surveys). A national mitigation strategy should recognize the need for an inter-agency organizational structure to ensure that the broad spectrum of needed activities is implemented effectively.