Brague DEMO: Flash flood and wildfire hazards in a Mediterranean catchment

Locations of the Brague river and other catchments and municipalities heavily touched by the Oct. 2015 flood disaster © NAIAD D6.1
Area characterisation: 

The Brague catchment region is located along the Mediterranean coast. A quite dense urban belt is located aside the shore, where all hilly catchments finish their way to the sea.

On 3rd, Oct. 2015, severe rainfalls triggered dramatic floods. Twenty peoples died, 550-650M€ of losses were observed, as well as cascading complications on transportation, communication and energy networks. This event will be used as a calibration case to study torrential flood hazards and risks and the effects of ecosystems on it.

NAIAD will concentrate the investigation effort on the Brague (61 km², 4 dead peoples in 2015, rural headwaters, forested central part and urban lowlands, numerous data on the event features, key impact of large wood jams).

Slideshow:

Land use in the Brague catchment: mixed suburban and forest cover © NAIAD D6.1 October 2015 flood extension and location of large wood jams which aggravated the flooding extension © NAIAD D6.1 Large wood jammed bridges and culverts and induced ecosystems dis-benefits © copyrights on each pictures
Objective: 

The public perception of ecosystems (e.g. forests, including possibly protecting ones) is strongly worsened following floods with massive wood jams. This case study aims at performing a comprehensive and in-depth analysis of a Mediterranean catchment to assess NBS benefits, dis-benefits and co-benefits and ways to optimize them.

Actions: 

The NAIAD project will help to better understand what occurred in details and in which extend Nature-Based Solutions may help to improve the situation. Among others, the three NAIAD partners mainly involved in the DEMO study will in particular:

  • Study risk and ecosystem perception through interviews and workshops,
  • Assimilate current initiatives and projects to optimize their NBS aspects,
  • Analyze the hydrological, hydraulics and related damages of management scenarios and highlight NBS pro and cons,
  • Analyze the cascading effects of wildfire and urban sprawling on hydrology,
  • Assess the flood risk on the case study accounting for climate change and cascading hazards,
  • Provide updated methods to valuate damages in flash floods contexts,
  • Provide methods to evaluate the co-benefit of NBS.
Potential impacts/benefits: 

A better knowledge of ecosystem mere, dis- and co- benefits should enable more comprehensive and integrated forest management in the both the riparian and hillslope areas. This will enhance:

  • Increase stakeholder awareness & knowledge about NBS.
  • Increase willingness to invest in NBS.
  • Increase awareness of NBS solution & their effectiveness and co benefits.

The better understanding of the catchment will also enable to tailor the protection system maximizing both green and grey solution effectiveness and efficiency for the aims of :

  • Increase quality and quantity of green and blue infrastructures.
  • Improve connectivity and functionality of green and blue infrastructures.
  • Increase Biodiversity.
  • Flood peak reduction.
  • Reduce flood risk.
Transferability of the result: 

The Brague catchment analysis can likely be transferred at various scales depending on the topics:

Topic

Scale

Effects of large wood on flood hazard aggravation

Global

Links between wildfire, urban sprawling and hydrology   Mediterranean

Damage curves for flash flood damage valuation

Mediterranean

NBS co-benefit analysis

French coast

Lessons learned: 

The case study is particularly rich in data on flash floods and related issues. The in-depth analysis will enhance our understanding of large wood-related flood aggravation. More lessons will emerge within the live time of the case study.

Contacts: 

Jean-Marc TACNET  (ThinkNature id :      jean-marc.tacnet)