RISK ASSESSMENT METHODOLOGIES FOR LANDSLIDES

Transcription

1 RISK ASSESSMENT METHODOLOGIES FOR LANDSLIDES Jean-Philippe MALET Olivier MAQUAIRE CNRS & CERG. Welcome to Paris! 1

2 Landslide RAMs Landslide RAM A method based on the use of available information to estimate the risk to individuals, property or the environment, from landslide hazards. A landslide RAMs generally contain the following steps: 1/ definition of threat (danger) 2/ estimation of probability of spatial occurrence (susceptibility) 3/ estimation of temporal probability of an event of a given magnitude (hazard) 4/ evaluation of the vulnerability of the element(s) at risk 5/ consequence identification 6/ risk estimation. It includes also the process of making a decision recommendation based on criteria/thresholds (tolerable/acceptable risks). Source: ISSMGE-ISRM-IAEG JTC-1 Joint Technical Committee on Landslides and Engineered Slopes, 2006

3 Example of a landslide RAM: French PPR methodology PPR: Plan de Prévention des Risques (1995) Philosophy: Qualitative approach Based on expert judgment of the scientist Use of available data & reports; no specific investigation Scale of work:1/ (or 1/5000 in urban zones) Procedure: Inventory of processes (type, activity, age, magnitude) Inventory of exposed elements & major stakes Hazard map = analysis of the type of processes, their activity, magnitude and frequency Risk map = hazard map x inventory of major stakes Criteria: reference event of 100 years Hazard & risk maps G3: high hazard / risk G2: moderate hazard / risk G: low hazard / risk Landuse planning regulation R3: Area with specific restrictions R2: Area with low restrictions R1: Area without specific restrictions

4 Example of a landslide RAM: French PPR methodology Hazard & risk mapping : debris flow & shallow slides Hazard map Risk zoning map G3: high hazard G2: moderate hazard G1: low hazard R3: Area with specific restrictions R2: Area with low restrictions R1: Area without specific restrictions

5 Example of a landslide RAM: French PPR methodology Hazard & risk mapping: coastal slides G3: high hazard G2: moderate hazard G1: low hazard Hazard map R3: Area with specific restrictions R2: Area with low restrictions R1: Area without specific restrictions Risk zoning map

6 Review of current landslide RAMs for EU27 Questionnaire and litterature review 27 questions, 4 themes 1. General information about risk assessment 71 questionnaires / 30 answers success rate: 43% 3. Description of the RAM 2. Data: Landslide inventory, conditioning factors, triggering factors, damages 4. Output documents

7 Review of current landslide RAMs for EU27 Landslide RAMs available for 18 EU Member States + Switzerland - Official RAM: 5 countries (France, Italy, Sweden, Switzerland, Austria) - RAM in development: 9 countries (Belgium, Cyprus, Czech Republic, Hungaria, Ireland, Slovakia, Slovenia, Spain, and United- Kingdom) - RAM used by R&D institutes / private companies: 4 countries (Germany, Greece, Poland, and Portugal) - No RAM: 6 countries (Denmark, Germany, Latvia, Lituania, Malta, Netherlands) - Information missing: Luxembourg, Finland

8 Review of current landslide RAMs for EU27 RAMSOIL Report: fact sheet describing the status of landslide RAMs per country Countries with an official RAM used in practice Countries with an official RAM in development Countries with local RAMs used by research institutes or private companies

9 Common characteristics of each landslide RAMs Indicators & spider graphs approach Input data: Topography & derived slope classes Soil map, Bedrock map (eg. lithology) Landcover Occurrence density of landslides Data processing: qual. approach Field geomorphologic analysis Combination of index maps Output information (documents): Geomorphological map S / H / R map (often, 3 classes of H / R) FRANCE ITALY SWITZERLAND SWEDEN Techniques: Inventory (historical archives, field observations, aerial photointerpretation, remote-sensing) GIS-based models Perception: Criteria / Threshold / Value judgment Common principles in landslide RAMs: - Data collection - Use of available data - Scale for risk zoning (1:10,000) - Data processing - Expert heuristic method - Based on principle of causality - Use of cost efficient methods

10 Objectives of the CERG Project - Update the information obtained in the RAMSOIL Project ended in Extent the information to the CoE Member States (47 MS) - Active role of ISPU / Florival - to contact different representatives in the MS (ISPU is used by EC & CoE for such activities) - to host the questionnaire on-line on their website, and store the data - to analyse the answers

11 THANKS FOR YOUR ATTENTION. Welcome to Paris! 11

12 Common characteristics of the landslide RAMs All RAMs: susceptibility zoning - Location, volume and classification of existing landslides - Location, volume and classification of potential landslides - Areas with a potential to experience landsliding in the future (travel distance head retreat) Landslide inventory map Landslide susceptibility map Some RAMs: hazard zoning Estimated temporal frequency (annual probability) Intensity frequency relationships Landslide hazard map All RAMs: risk zoning Elements at risk Vulnerabillity Spatial and temporal probability Potential damage Landslide risk map