Pilot Sites - Orleans
Due to the extent of the Loire flood plain, the Ville d’Orleans has established Flood Risk Management as one of its top priorities. Today, Orleans is committed to reducing its vulnerability by taking new adaptive approaches to sustainable flood risk management and flood risk management planning. During the recent years, the City of Orleans has been working on flood issues through information campaigns, spreading knowledge about floods in the communities and raising awareness. It is also putting in place rescue and recovery plans for the population and public services. The aim is to minimise damages and enable the City to recover as quickly as possible after flood events.
The three organisations which are working together have the following aims:
The Conseil Général de Loiret started a preliminary investigation of flood risk and its management in the “Middle Loire” shortly after the turn of the century. This preliminary stage which scopes and quantifies the work associated with flood risk management has also identified the organisational requirements within the Conseil Général de Loiret which employes over 2,000 people. The second, operational stage of the project is now under way. This work is being carried out in parallel with the Agglomération d’Orléans” and Ville D’Orleans which work at different scales. The State (Prefecture) is also carrying out similar work and the “Etablissement Public Loire” which works over all the Loire river basin and which includes 19 “départements”, has included actions in its priorities which financially and technically support the resilience of public infrastructure networks. The aim is to develop the emerging dynamic at all grades of the administration to address this issue of resiliency within the public services, utility organisations and the wider public.
The work with the wider public aims to increase their awareness of flood risk and how to reduce their vulnerability to flooding. This will be achieved by means of modelling to identify the probability and consequences of flooding within flood plains within which some 48,000 people lived and work. Other work will help to speed the process of restore normal life once a flood occurs, including the resumption of sewerage services by reduction of their vulnerability.
It is also intended to raise awareness and resilience through the promotion of a civil defence reserve that will be integrated with the Local Flood Rescue Authority.
In addition to the risk associated with river flooding, there are also concerns about the impact of rising ground water levels. Therefore it is intended to carry out ground water modelling to help assess the joint probability of flooding from both sources. Finally, a communication strategy will be developed to raise the awareness of the politicians, professionals and the general public to take adaptive measures in association with the spatial planning and development of the city.
The main aspects of relevance to the FloodProBE work programme are:
Conseil Général du Loiret, Agglomération of Orleans and City of Orleans are involved in a policy of vulnerability assessment and reduction. They focus their activity in reducing vulnerability of:
- Buildings(houses, flats, companies...);
- Networks(energy supply, drinking water, sewer, roads...);
- Public services like waste management.
FloodProBE WP2 is focused on such activities and these three stakeholders are very interested in the deliverable that will be produced. Testing and assessing the results of WP2 on Orleans Region is wished by the three stakeholders.
Also, due to the extent of the Loire flood area, the three stakeholders would like to test the deliverable of task 4.2 dealing with concepts and technologies for damage mitigation and improved flood resilience and for integrated shelter functions in the urban built environment.
DREAL Centre is managing the flood defence assets in the Orleans Region. Most of the flood defences are earth embankments, with a lot of particular infrastructures integrated in the embankments and creating weak spots at the interfaces.
Under WP3, the development of improved understanding of failure processes, the piloting of the use of geophysical methods and the development of integrated assessment methods can all be trialled on the Orleans Region embankments and provide feedback as to their usefulness/appropriateness, particularly in regard to understanding fragility and breach.
In 2003, the Loire upstream of Orleans partly overflowed some urban and countryside areas with different impacts on buildings, levees and networks. The 2003 flood event was a medium return period: 1/20 (3200 m3/s). In terms of flood risk management, actors were totally surprised and disorganised. Since that event, politicians start to be aware of the possibility of a major flood.
As a consequence of the flood in 2003, the crucial challenges cover mainly:
- Analysis of the vulnerability of critical infrastructures;
- Detailed assessment of levee performance
Objectives & Actions
The objectives of the research realised at the pilot site were identified to cover the challenges. The related actions performed at the pilot site were as follows:
- Analysis of the most vulnerable infrastructures with respect to floods: The objective was to analyse road network vulnerability. In this way, new graph theory indicator has been designed and implemented.
- Analysis of the flood embankment structure transitions: The research work on transitions focused on identification of different types of flood defence structure transitions, their weaknesses and potential remedial measures.
- Rapid, non-intrusive geophysical methods for dike performance assessment: Within this action cross tests of different geophysical methods were performed by two partners on two sections of levees, one in an urban context and the other in a semi-rural context.
- Using Helicopter-Borne LiDAR to Contribute to Levee Assessment: With the financial support of two local partners (DREAL Centre and SNCF), this action tested the very high resolution helicopter-borne laser remote sensing technology as suitable for contributing to the assessment process of urban and suburban levees.
- Combination of information sources for dike diagnosis in a GIS: The research under this activity looked at how different types of data and information may be combined to improve the performance assessment of levees. Some examples were drawn from Loire levees and associated tools in use by the local levee manager (DREAL Centre)
Concerning analysis of critical infrastructures, the FloodProBE project confirmed the specific interest of Orleans for road networks vulnerability analysis. Using the method of redundancy indicators developed in FloodProBE new vulnerable areas have been identified. All technical methodologies developed within the other performed activities of FloodProBE project have been directly implemented in the practice of the DREAL Centre, the organisation in charge of managing Loire levees. The timing of the project was in concordance with the new mandatory needs of producing hazard studies for classes A and B levees before end of year 2012 and 2014 respectively. Maps of global breach probabilities such as follows are the basic tool for prioritising reinforcement work programs in the coming years, keeping funding to be the only limiting aspect.
For further information take a look at the following links:
Identification and analysis of most vulnerable infrastructure in respect to floods
Reliability of Urban Flood Defences
Rapid and cost-effective dike condition assessment methods: geophysics and remote sensing