Sediment and woody debris transport regulation in torrential catchments: case study of an alpine torrent

Transcription

1 EFC-FAO WP MMW - Working Group II Practitioners workshop #3 Sediment and woody debris transport regulation in torrential catchments: case study of an alpine torrent Argentine (Savoie) France - June 7th to 9th, 2017

2 Welcome to Savoie! Administrative Region of Auvergne-Rhône-Alpes Department of Savoie: 90% of mountainous area Chamousset Argentine Saint Jean de Maurienne inhabitants km² Wikipedia Le Dauphiné Libéré

3 Framework of the workshop Working group 2 has been created in 2013 within the WP MMW to improve cooperation between European practitioners in the field of natural hazard management in mountain areas Objective is to build capacities of technical human resources (especially practitioners) through a joint analysis/discussion of practices and techniques related to natural hazards in mountain areas Led by Austria (Federal Ministry Of Agriculture, Forestry, Environment And Water Management) and France (ONF RTM) First Phase ( ): 2 workshops + extra activities Second phase ( ): 2 workshops foreseen News and products are published at:

4 Lesson learned from Salzburg (Austria May 2016) Workshop 2: Woody Debris Questions and answers Joint identification of challenges and potential solutions in the context of woody debris Country presentations related to WD management Field trip Discussion/recommendations Main findings: Comparison of national contexts/regulations/ methods related to WD management allowed to observe similarities as well as substantial differences between alpine countries different types/groups of catchments that require different approaches regarding woody debris management Various processes leading to woody debris require different measures in managing it (riverbank erosional, landslides, debris flows, avalanches )

5 Lesson learned from Salzburg (Austria May 2016) Non- technical recommendations Forestry measures have a more sustainable and ecological effect on watercourse stability. More research on the particular influence (positive or negative) of trees and vegetation on the stability of watercourse plus embankment and of dead wood within the immediate discharge section should be conducted Efficacy of regular inspection of torrents has been proven Risk of bridges or other obstacles clogging has to be taken into account in hazard zone mapping Give back space to rivers and torrents

6 Lesson learned from Salzburg (Austria May 2016) Technical recommendations keep in mind possible negative influences of technical measures (erosion, river bed level, sediment transport, ecological permeability) when planning and designing technical structures When designing discharge profiles, take into account possible higher impacts or an increase of the design event discharge Regulations on construction and designing elements of technical structures related to woody debris should be elaborated Work on regulations, technical guidelines or estimation formulas to calculate/estimate the amount and volumes of woody debris Possibilities and capabilities of net or cable based structures for woody debris retention should be investigated. Best by analyzing the functionality of existing structures (e.g. Rienza gorge, Italy)

7 3 rd workshop Sediment and woody debris transport regulation in torrential catchments: case study of an alpine torrent > Visit of an existing structure for sediment/woody debris regulation > Case study of the torrent of La Balme Put into practice general and technical recommendations elaborated during Salzburg Workshop Compare approaches, methodologies and structures implemented by the countries for the addressed issue Develop a common proposal of a technical structure

8 Program of the 3 rd workshop Day 1 (June 7th) 14:00 Workshop opening Presentation of the detailed program and objectives of the workshop General presentation of the region and overview of the studied watersheds Introduction to the visit (Arvan structure) 15:00 - Visit of a recent structure designed to control sediment transport and woody debris deposit on Arvan River, upstream of the confluence with the Arc River. 19:30 - Dinner at hotel

9 Program of the 3 rd workshop Day 2 (June 8 th ) 8:00 Country presentations of Albania and Turkey (Hotel conference room) 9:00 Introduction to the case study: Presentation of the characteristics of the Torrent de la Balme catchment, Overview of the results of achieved studies: 1) Assessment of natural hazards and 2) hydraulic study, 10:00 Definition of the groups and departure to field work (Argentine) 16:00-17:00 Debriefing by group at the hotel 18:00 Visit of the medieval city of Conflans and dinner

10 Program of the 3 rd workshop Day 3 (June 9 th ) - hotel conference room 8:00 Technical measure developed in similar contexts (Austria, Bavaria) 8:45 Proposals of technical measures for the case study of La Balme Torrent: Preparation of proposals (in groups) Presentation of the results of each group 11:00 Discussion and elaboration of common recommendations 11:30 Conclusion Discussion on valorization/diffusion of results 12:00 Closing of the workshop Route to Airport

11 RTM department : Within the National Forest Office, a specialized department for the prevention and protection against natural hazards in mountain areas Origin : 1860 : law on afforestation of mountainous areas (1,4 M ha ) 1882 : law on restoration and conservation of mountainous areas Organization At the beginning, a special afforestation department within the Water and Forestry Administration 1965 : National Forest Office (ONF) manages French public forests (State or local communities), 1972 : a special RTM department is created within the ONF with the task of surveying and maintaining the public structures related to natural risks prevention.

12 RTM organization : Since 01/01/2017, 3 RTM agencies (Northern Alps, Southern Alps, Pyrenees), covering 11 departments A national technical direction on natural hazards, 104 professionals (technicians & engineers) ha of RTM public forests (managed by the ONF department) individual structures displayed in sites

13 RTM department missions : National missions of general interest Maintenance of structures in public RTM forests (Ministry of Agriculture) Monitoring, maintenance, strengthening ( structures) watershed risks studies Management database

14 National missions of general interest Phenomena knowledge (Ministry of Environment) Snow avalanche observations Event records and database ( events for sites): Technical support to Prefects and local municipalities (Ministries of Environment, Interior) Land-use planning taking into account natural hazards, Crisis management, Technical support for Ministries (Agriculture, Environment) Expertise Methodological guidelines International actions

15 Private engineering Project management for local municipalities Protective structures Expertise and studies Risk analysis (torrential, geological, snow avalanche hazards) Field expertise

16 Thanks for your attention