samedi 27 mars 2010
Key Findings of Workshop on Rebuilding for Resilience: How Science and Engineering Can Inform Haiti's Reconstruction
March 22-23, 2010
University of Miami, Coral Gables, Florida
The devastation caused by Haiti’s January 12 earthquake underscores the need to operationalize the principle of disaster risk reduction and to incorporate disaster mitigation into all aspects of reconstruction. Rebuilding efforts must not only focus on providing shelter and services but also on strengthening the resilience of the Haitian people and their communities to future earthquakes and other natural hazards.
What follows are key findings that will inform decisions of the March 31 International Donors’ Conference towards a New Future for Haiti. These messages emerged from two days of interdisciplinary dialogue at a workshop that brought together over 100 scientists, engineers, planners and policy makers drawn from government and non-governmental organizations, development agencies, the business, engineering and science communities, and academia. The deliberations benefited greatly from the active participation of a delegation comprised of Haitian government officials and academia.
The workshop identified key issues in four areas that are fundamental to the process of responsible reconstruction of Haiti: a) rebuilding requirements related to hazard assessment, b) adequate engineering of buildings and critical infrastructure, c) long-term data needs, and d) capacity building.
Convened by the U.S. National Science and Technology Council’s Subcommittee on Disaster Reduction, the workshop was co-sponsored by the U.S. Department of State, the U.S. Agency for International Development and the United Nations International Strategy for Disaster Reduction, and by the IRIS Consortium with support from NASA, the National Science Foundation, and the U.S. Geological Survey. Additional information on the workshop is available at
Hazard Assessment for Earthquakes, Inland Flooding, and Landslides
Earthquakes, inland flooding and landslides are the three greatest hazard concerns associated with resettlement, recovery, and initial reconstruction in Haiti. (Additional hazards are discussed elsewhere in this document.)
- Hazards, Vulnerability, Risk, Planning – Hazard assessment is the first step in improving lives through vulnerability and risk assessments, all of which need to incorporate locally-identified societal needs. Hazard maps are the point of departure for vulnerability assessments leading to risk assessments, which are to be used in land-use planning for development and reconstruction. Varying values of financial and social risk will result in planning for different levels of protection (hospitals require different standards than marketplaces).
- Maps of primary hazards exist and should be used – Preliminary maps for these three hazards have been developed, including probabilistic seismic hazard maps, and should be used to guide local standards of building and infrastructure. Haiti is also subject to hurricane and tropical-storm force winds, coastal subsidence and lateral spreading, tsunami, and drought, and preliminary maps for many of these hazards exist, or can be prepared.
- These maps will be refined, in partnership among Haitians and others – Long-term investment and development require the expansion and refinement of natural-hazard analysis in Haiti (and the region) as we move forward. For example, we need to improve the seismic hazard maps to incorporate amplification due to soil conditions and liquefaction potential. Refined versions of the current hazard maps will be created over the coming year, based on studies that should be done in partnership by foreign and Haitian experts, leading to long-term capacity for continuing improvement.
- Flooding and debris flows hazards are on the rise – Given the severity of human impacts to the Haitian landscape related to deforestation and soil degradation and erosion, the risks associated with flooding and mass movements (such as landslide and debris flow) are greater than would be expected from historical experience and are likely to increase more as a consequence of climate change. Temporary settlement and reconstruction along rapidly aggrading rivers and on unstable slopes should be avoided.
- Critical sites require additional studies – For the most critical sites, individual studies will be needed to locally refine these preliminary maps.
Engineering Issues for Buildings and Critical Infrastructure
The workshop identified four aspects of the rebuilding challenge from an engineering perspective:
Owner-built new construction
- Owner-built construction represents 80 to 90% of the construction within Haiti, and thus building back better in Haiti requires improvements to the owner-built construction process.
- Use better building materials – The construction materials and practices currently used in Haiti (i.e., reinforced concrete and concrete blocks) can be improved to build structures that are resistant to both earthquakes and hurricanes.
Improve construction methods – Specific improvements to construction methods should be identified (e.g., tamping of concrete to remove voids), as well as appropriate features of the structural details (e.g., reinforcement locations).
- Provide examples of home designs – Five to ten standard prescriptive designs should be developed, each of which includes engineering drawings and building instructions, so that owners do not need to develop specific building plans that incorporate appropriate detailing.
- Provide training and demonstration projects – Improvements to construction practice will require hands-on training sessions and demonstration projects at vocational schools (e.g., masons school) and local communities, as well as follow up visits to ensure that the improvements are being implemented.
- Provide incentives for proper implementation – Incentives for implementing the developed improvements must be identified.
- Study improved designs for future development – In the long term, considerations should be given to alternative types of structures and more sustainable solutions, using partnerships of Haitian and foreign designers.
New engineered infrastructure
Infrastructure represents a wide range of facilities, including civic buildings (e.g. schools, hospitals, government buildings), bridges, ports, water distribution systems, power generation and distribution systems, drainage systems, waste-water collections systems, and solid waste management systems.
- Use seismic engineering – Due to the importance of infrastructure facilities, they should be seismically engineered using appropriate design codes.
- Adopt and/or modify existing design codes – This process requires adoption/modification of existing design codes for the unique setting in Haiti, and the adopted design code must use appropriate hazard estimates (e.g., ground-shaking design levels derived from seismic hazard maps) as the basis for design.
- Work within regulatory framework with trained personnel – The design code needs to be implemented within an appropriate regulatory framework that includes certification, inspection, and enforcement. Enforcement of building codes will require capacity building of municipal engineers, and public works department engineers and construction industry workers such as masons, carpenters, and contractors.
- Encourage sustainable practices – Sustainable practices should be used whenever possible.
Rehabilitation of existing buildings and infrastructure
Throughout the country (both within and beyond the earthquake affected area), buildings and infrastructure are at risk of collapsing in the next earthquake. Buildings that survived the Jan. 12 earthquake are not necessarily earthquake-resistant.
- Assess buildings and infrastructure – An assessment of the seismic vulnerability of existing buildings and infrastructure must be undertaken, and structures found to be deficient must be rehabilitated. These assessments should initially target essential facilities (e.g., civic buildings, institutional infrastructure, historic buildings) that are important to the population as a whole.
- Identify retrofitting methods applicable to Haiti – Cost-effective rehabilitation strategies should be identified that are appropriate for the structural conditions in Haiti.
- Provide demonstrations of rehabilitation effectiveness – Demonstrations should be developed (e.g., videos of shaking table tests that compare the responses of non-rehabilitated and rehabilitated structures) that illustrate the effectiveness of rehabilitation.
- Identify and implement incentives for compliance – Incentives for rehabilitating existing buildings should be identified and implemented, in order to encourage participation in resilient reconstruction.
Landslide and liquefaction mitigation
Landslides and liquefaction represent hazards in which the ground fails, generating significant damage. Landslides are a concern in steeper terrain and can be triggered by various mechanisms including rainfall and earthquakes. Liquefaction occurs in saturated, loose sand when earthquake shaking is large enough to temporarily transform the soil into a liquid-like state.
- Identify susceptible areas – Areas prone to landslides and liquefaction should be identified through the integration of geologic data, soil data, and topographic data, and measures should be taken to minimize the risk posed by these hazards, either through enforced zoning or mitigation measures.
- Improve soil in reclaimed land – Reclaimed land, such as the area around the port, is particularly prone to liquefaction, and measures should be taken to improve the soils in these areas.
- Improve embankments and other structures – Soil fill materials used in road embankments and bridge approaches, as well as soft soils underlying roadbeds, may move considerably during an earthquake, resulting in roads that are impassible. These embankments and fill materials should be seismically engineered to perform better during earthquakes.
The value of international investments in hazard-resistant structures will be greater if investments are also used to strengthen the country’s social and institutional capacity in order to endow broad cross-sections of Haitian society with the knowledge and resources to continually reduce the country’s vulnerability to natural hazards well into the future. Build communities, not just houses.
- Provide direct financial support for education and training – Capacity building should be promoted with direct financial support for education, training and outreach, including programs for local masons, other vocational training, adult literacy, primary and secondary education, universities, and development of the Haitian science and engineering communities.
- Preserve cultural heritage and social strengths – Haiti’s cultural heritage should be preserved throughout the rebuilding process, but the country’s recovery should also be transformative. Recognizing that widespread internal displacement has weakened many communities, perform assessments of social capital to determine needs at the local level.
- Solicit community participation– Local communities should be engaged in a participatory planning process to promote buy-in for the reconstruction plan, a sense of ownership for rebuilding efforts, and build capacity through direct engagement with reconstruction issues.
- Communicate facts of hazards – Assistance projects should budget for communication and outreach that works to dispel rumors about hazard risk and promotes risk-wise behavior. Communication of the hazards is essential, and education of the people and development agencies should accompany widespread distribution of hazard maps and promulgation of construction standards.
- Use local markets – Leverage local markets for cost savings to avoid high international transaction costs, promote business continuity, and stimulate the local economy.
- Budget for hazard mitigation, reducing impacts of future events – Allocate a portion of the rebuilding budget for sustained hazard mitigation, recognizing that much of the future vulnerability to hazards is represented by structures and communities not immediately impacted by the last event.
Long-Term Data Needs
In addition to identifying the existing hazard assessment tools that can be used to inform
investments in rebuilding, the workshop also identified a number of areas where additional data acquisition is needed to refine hazard zonation, recurrence frequency, and city master planning based on identifying areas of significant risk from various hazards. Major data needs for improved risk and vulnerability assessments include:
- Improved topographic and bathymetric information – The currently available 90-meter resolution Shuttle Radar Topography Mission (SRTM) data are not sufficient. Higher-resolution SRTM data exist and should be released. There is an associated need for still higher-resolution light detection and ranging (LIDAR) acquisition in key hazard-prone areas.
- Remote-sensing data and studies – Continued and enhanced remote sensing observations are required to monitor and update hazard assessments. Satellite-based optical and synthetic aperture radar observations are needed to support field observations and to monitor surface deformation associated with strain accumulation and mass movements.
- Field surveys for geology and soil classifications – Soil type and texture information is essential for slope-stability studies, reforestation planning, determination of site-specific seismic shaking amplification, and flood modeling.
- Monitoring networks for multiple hazards – Reconstruction plans need to invest in a long-term program for development of monitoring capabilities, which must include a strong Haitian local capacity and infrastructure for long-term viability. In-situ networks of rain and river gauges are required for analysis and model verification for use in flooding and landslide hazard evaluation, as well as for agricultural and hydro power optimization. Seismograph and GPS networks are required for improving the assessment of earthquake and related hazards. Social tracking data are needed to improve vulnerability assessments and evaluate adoption of risk-wise behavior.
- Consideration of geophysical drivers of natural hazards – Scientific observations and analysis are inherently regional in scope; natural hazards know no borders. Targeted investment in a regional capability that incorporates and builds upon capacity developed in Haiti will improve the sustainability of monitoring activities. This is an important consideration for hazards that have long recurrence intervals in any one location but have devastating impacts when they strike. The regional approach should leverage existing networks, infrastructures, organizations and social capacity to the extent possible and should facilitate access to the information generated.
mercredi 17 mars 2010
vendredi 12 mars 2010
Voici un document qui ne manquera pas de vous intéresser. Il est issu de l'Association française du génie parasismique (AFPS):
Haïti-après séisme ---> CPSMI/Antilles/AFPS.
Visitez aussi le site Web de l'AFPS: afps-seisme.org.
L'AFPS a aussi a aussi un guide pour la protection parasismique des ponts, mais il faut le commander (AFPS 1992. Pour ce faire, se référer au site Web de l'AFPS.
mardi 9 mars 2010
February 23, 2010
A field reconnaissance in Haiti by a five-member team with expertise in seismology and earthquake engineering has revealed a number of factors that led to catastrophic losses of life and property during the January 12, 2010, Mw 7.0 earthquake. The field study was conducted from January 26 to February 3, 2010, and included investigations in Port-au-Prince and the heavily damaged communities to the west, including Léogâne, Grand Goâve, Petite Goâve, and Oliver.
Seismology: Despite recent seismic quiescence, Haiti has suffered similar devastating earthquakes in the historic past (1701, 1751, 1770 and 1860). Haiti had no seismograph stations during the main earthquake, so it is impossible to estimate accurately the intensity of ground motions. Nonetheless, the wide range of buildings damaged by the January 12, 2010 earthquake suggests that the ground motions contained seismic energy over a wide range of frequencies. Another earthquake of similar magnitude could strike at any time on the eastern end of the Enriquillo Fault, directly to the south of Port-au-Prince. Reconstruction must take this hazard into account.
The four portable seismographs installed by the team recorded a series of small aftershocks. As expected, the ground motions recorded at a hard rock site contained a greater proportion of high frequencies than the motions recorded at a soil site. Two of the stations continue to monitor seismic activity.
A thorough field investigation led the team to conclude that this earthquake was unlikely to have produced any surface rupture.
Geotechnical Aspects: Soil liquefaction, landslides and rockslides in cut slopes, and road embankment failures contributed to extensive damage in Port-au-Prince and elsewhere. A lack of detailed knowledge of the physical conditions of the soils (e.g., lithology, stiffness, density, and thickness) made it difficult for us to quantitatively assess the role of ground-motion amplification in the widespread damage.
Buildings: The Haitian Ministry of Statistics and Infomatics reported that one-story buildings represent 73% of the building inventory. Most ordinary, one-story houses have roofs made of sheet metal (82%), whereas most multi-story houses and apartments have roofs made of concrete (71%). Walls made of concrete/block/stone predominate both in ordinary houses and apartments.
It appears that the widespread damage to residences, and commercial and government buildings was attributable to a great extent to the lack of attention in design and construction to the possibility of earthquakes. In many cases, the structural types, member dimensions, and detailing practices were inadequate to resist strong ground motions. These vulnerabilities may have been exacerbated by poor construction practices. Reinforced concrete frames with concrete block masonry infill appeared to perform particularly poorly. Structures with light (timber or sheet metal) roofs performed better compared with structures with concrete roofs and slabs.
The seismic performance of some buildings was adequate, and some of the damaged buildings appeared to have had low deformation demands. These observations suggest that structures designed and constructed with adequate stiffness and reinforcing details would have resisted the earthquake without being damaged severely.
A damage survey of 107 buildings in downtown Port-au-Prince indicated that 28% had collapsed and another 33% were damaged enough to require repairs. A similar survey of 52 buildings in Léogâne found that 62% had collapsed and another 31% required repairs.
Bridges: There was no evidence of bridge collapses attributable to the earthquake. Most bridges in Port-au-Prince are simple box culverts consisting of 2.0 to 2.5 meter (6 to 8 ft) deep box girders. However, in several cases the roadway settled differentially between the approaches and the section spanning the culvert. Multi-span bridges on primary routes are engineered structures that experienced some damage but are still serviceable.
Port Facilities: The main port in Port-au-Prince suffered extensive damage during the earthquake, inhibiting the delivery of relief supplies. The collapse of the North Wharf appears to have been caused by liquefaction-induced lateral spreading. The westernmost 120 meters (400 ft) of the South Pier collapsed, and approximately 85% of the vertical and batter piles supporting the remaining section were moderately damaged or broken. The remaining section of pier was shut down to vehicle traffic following additional damage that occurred during an aftershock. The collapse of a pile-supported pier at the Varreux Terminal resulted in the deaths of about 30 people working on the pier at the time of the earthquake. Less severe damage, including a small oil spill, occurred at a marine oil terminal located near Port-au-Prince.
Damage to Institutions: The functioning of the government and social infrastructure was seriously deteriorated by the loss of personnel, records and facilities. Such losses occurred in numerous clinics, hospitals, police stations, schools, universities, palaces, ministries and churches. These losses have compromised the recovery and reconstruction efforts.
Satellite Imagery: The use of remote sensing data, including satellite and aerial imagery, proved highly effective in assisting damage assessment, evaluating the extent of landslides, and guiding rescue and recovery efforts. Light Detection and Ranging (LIDAR) technology has been effective to create three-dimensional images for damage assessment and rebuilding operations.
Conclusions: The massive human losses can be attributed to a lack of attention to earthquake-resistant design and construction practices, and the poor quality of much of the construction. The historic pattern of earthquakes in Haiti indicates that an earthquake of magnitude 7 or larger could strike southern Haiti near Port-au-Prince at any time. Reconstruction must therefore be based on sound, simple and cost-effective engineering practice for all possible natural hazards. These principles must be clearly communicated to the citizens of Haiti. Additional fact gathering is needed, both to quantify the January 12th fault rupture and earthquake history (inputs to calculations of future earthquake probabilities), and to more comprehensively evaluate damage to buildings and infrastructure, so as to inform decisions about reconstruction.