D6.2 from Hazard to Risk: Models for the Demos - Part 6 -France -Brague Catchment Guillaume Piton, S
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D6.2 From hazard to risk: models for the DEMOs - Part 6 -France -Brague catchment Guillaume Piton, S. Dupire, Alexandre Mas, Roxane Marchal, David Moncoulon, Thomas Curt, Z.X. Wang, T. Onfroy, Jean-Marc Tacnet To cite this version: Guillaume Piton, S. Dupire, Alexandre Mas, Roxane Marchal, David Moncoulon, et al.. D6.2 From hazard to risk: models for the DEMOs - Part 6 -France -Brague catchment. 2018, pp.476. hal- 03026632 HAL Id: hal-03026632 https://hal.inrae.fr/hal-03026632 Submitted on 26 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Deliverable 6.2 From hazard to risk: models for the DEMOs PART 6 France – Brague catchment Pages: 215 – 344 Should you wish to use or refer to it, please cite as follows: Piton, G., Dupire, S., Arnaud, P., Mas, A., Marchal, R., Moncoulon, D., Curt, T., Wang, Z-X., Onfroy T., & Tacnet, JM. (2018): “DELIVERABLE 6.2 From hazards to risk: models for the DEMOs - Part 3: France: Brague catchment DEMO”. EU Horizon 2020 NAIAD Project, Grant Agreement N°730497 D6.2 From hazard to risk: models for the DEMOs NAIAD GA nº 730497 Part 6 - France – Brague catchment CONTENTS LIST OF FIGURES ........................................................................................................................ 216 LIST OF TABLES .......................................................................................................................... 219 Abstract ..................................................................................................................................... 221 1 Introduction ...................................................................................................................... 222 1.1 General information .................................................................................................. 222 1.2 Wildfire hazards ........................................................................................................ 222 1.3 General information on flood risks ........................................................................... 223 1.4 Hydrological modelling .............................................................................................. 224 1.5 Hydraulics .................................................................................................................. 225 1.6 Protection strategies ................................................................................................. 225 2 Wildfires assessment methods ......................................................................................... 227 2.1 Time and spatial scales .............................................................................................. 227 2.2 Vegetation types and fire history .............................................................................. 228 2.3 Fire weather hazard modelling ................................................................................. 232 2.4 Fire scenarios for cascading effect assessment on hydrological processes .............. 238 3 Hydrology .......................................................................................................................... 240 3.1 Rainfall modelling ...................................................................................................... 240 3.2 Surface runoff methods ............................................................................................ 244 3.3 River discharges......................................................................................................... 248 4 Hydraulics .......................................................................................................................... 259 4.1 Existing reports .......................................................................................................... 260 4.2 Simplified direct analysis: The Flood Excess Volume (FEV) ....................................... 261 4.3 Advanced modelling: IBERwood 2D model ............................................................... 272 5 Exposition to flood and runoff risks results ...................................................................... 295 5.1 CCR flood claim database .......................................................................................... 295 5.2 Exposition to flood and surface runoff from the 2015 event CCR ............................ 295 5.3 Runoff model results ................................................................................................. 301 D6.2, Part 6 - Brague catchment 215 D6.2 From hazard to risk: models for the DEMOs NAIAD GA nº 730497 Part 6 - France – Brague catchment 6 Integrated flood protection schemes................................................................................ 309 6.1 Highlighting forest influence on hydrology through post-wildfire hydrological changes: an exploratory study of the France southern region ............................................................ 309 6.2 Lowlands’ flood protection strategies: Three options .............................................. 314 7 Conclusions ....................................................................................................................... 332 References ................................................................................................................................. 335 Appendix 1. Rainfall and discharge data ............................................................................... 340 LIST OF FIGURES Figure 1 : Map of the Brague catchment .................................................................................. 222 Figure 2 : Controls on fire at different scales of space and time. This framework adds a fire regime triangle (upper right) to the traditional triangles used to characterize combustion (lower left) and the fire environment (middle). Arrows represent feedbacks between fire and the forces controlling fire at different scales. ............................................................................................ 227 Figure 3 : Map of the land cover on the DEMO site (extracted from Corine Land Cover and the IGN BDForet) ............................................................................................................................. 229 Figure 4 : Brague wildfire on the period 1976-2016: monthly distribution of (a) the number of fires, (b) burned surfaces and (c) distribution of burned surfaces in numbers. ....................... 231 Figure 5 : Annual fire frequency and burned surface ratio for each square of the 2x2 km Prométhée grid during the period 1981-2016. ......................................................................... 232 Figure 6 : Structure of the Canadian Fire Weather Danger Rating System (CFFDRS) indices ... 233 Figure 7 : Empirical cumulated distribution function curves of the (a) Fire Weather Index (FWI) and (b) Fine Fuel Moisture Code (FFMC) values encountered on the days of fire recorded in the Prométhée database. Figures in brackets represent the different thresholds defining the fire weather danger levels. .............................................................................................................. 234 Figure 8 : Annual number of days with Fire Weather Index (FWI) and Fine Fuel Moisture Code (FFMC) exceeding thresholds, number of fires and burned surface on Brague catchment DEMO over the period 1973-2015. The temporal linear trend is shown with a dashed line if significant (the sum of all days of moderate to extreme fire weather is taken into account for FFMC and FWI temporal trends). ............................................................................................................... 236 Figure 9 : Spatio-temporal evolution of Fire Weather Index (FWI) and Fine Fuel Moisture Code (FFMC) in Brague catchment DEMO ......................................................................................... 237 Figure 10 : Map of the two biggest continuous forest entities within the Brague DEMO catchment ................................................................................................................................. 239 D6.2, Part 6 - Brague catchment 216 D6.2 From hazard to risk: models for the DEMOs NAIAD GA nº 730497 Part 6 - France – Brague catchment Figure 11 : The October 2015 isohyets for the related thunderstorm, the Brague catchment is displayed in red ......................................................................................................................... 241 Figure 12 : Rainfall height on Oct. 3rd between 20:00 and 23:00, location of sub-catchments, taken from Cabinet Merlin (2016b) .......................................................................................... 242 Figure 13 : Regional parameter of the rainfall generator in the Brague DEMO area, example of the PJMAX-Summer parameter ................................................................................................ 243 Figure 14 : Maps of the rainfall generator parameters in the Brague DEMO area................... 243