Charlotte Heinzlef

Damien Serre

Urban resilience: From a limited urban engineering vision to a more global comprehensive and long-term implementation

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

In a context of climate change, urban areas are facing an increase in the recurrence and intensity of disasters. Among these disasters, floods have impacted up to 2 billion people over the period 1998[START_REF] Loireau | Co-construction du concept d'observatoire scientifique en appui aux gestionnaires de territoire: OSAGE[END_REF](European Environment Agency, 2017). Faced with these challenges and related uncertainties, urban areas are increasingly vulnerable to urban networks disruption risks. These disruptions can therefore produce cascading effects, impacting areas that were originally not at risk or vulnerable (Boin and MacConnell, 2007). These service disruptions weaken urban areas and activities and raise questions about risk management. Risk management in itself has had to evolve in order to adapt to these "new" risks and uncertainties related to climate change and the concentration of issues (economic dynamics, buildings, infrastructure, assets, social dynamics, political trends, etc.) in urban areas. The concept of resilience has therefore been gradually integrated into risk management in order to prepare territories and populations for the increasing hazards and their consequences to relaunch an activity. Resilience has been integrated into risk management since the 2000s [START_REF] Campanella | Urban Resilience and the Recovery of New Orleans[END_REF], but it is still an unclear concept today and poorly integrated into risk management strategies. A variety of definitions exist today in hopes of clarifying the concept of resilience [START_REF] Meerow | Defining urban resilience: A review[END_REF]. Belonging to multiple disciplines [START_REF] Alexander | Resilience and disaster risk reduction: an etymological journey[END_REF], resilience in risk management can at the same time be related to capacities of resistance to shock [START_REF] Serre | DS3 Model Testing: Assessing Critical Infrastructure Network Flood Resilience at the Neighbourhood Scale[END_REF], absorption [START_REF] Cardona | The Need for Rethinking the Concepts of Vulnerability and Risk from a Holistic Perspective: A Necessary Review and Criticism for Effective Risk Management1[END_REF], adaptation [START_REF] Pelling | The vulnerability of cities: natural disasters and social resilience[END_REF], reactivity [START_REF] Pickett | Resilient cities: meaning, models, and metaphor for integrating the ecological, socio-economic, and planning realms[END_REF], reconstruction [START_REF] Walker | Resilience, Adaptability and Transformability in Social-ecologial Systems[END_REF], learning [START_REF] Carpenter | From Metaphor to Measurement: Resilience of What to What?[END_REF][START_REF] Klein | Resilience to natural hazards: How useful is this concept?[END_REF], rebound [START_REF] Davoudi | Resilience: A Bridging Concept or a Dead End? "Reframing" Resilience: Challenges for Planning Theory and Practice Interacting Traps: Resilience Assessment of a Pasture Management System in Northern Afghanistan Urban Resilience: What Does it Mean in Planning Practice? Resilience as a Useful Concept for Climate Change Adaptation? The Politics of Resilience for Planning: A Cautionary Note: Edited by Simin Davoudi and Libby Porter[END_REF], etc. The main idea is that a system [START_REF] Sayers | Flood Risk Management, A strategic Approach[END_REF] is resilient if it recovers from a shock by limiting the negative impacts [START_REF] Butler | A New Approach to Urban Water Management: Safe and Sure[END_REF] and subsequently restarts activities. Defined as the capacity of a territory and its population to plan for, adapt, absorb, recover from, learn and evolve (UNISDR, 2009;[START_REF] Cardona | The Need for Rethinking the Concepts of Vulnerability and Risk from a Holistic Perspective: A Necessary Review and Criticism for Effective Risk Management1[END_REF]Pelling, 2011, Walker and[START_REF] Walker | Resilience thinking: sustaining ecosystems and people in a changing world[END_REF][START_REF] Carpenter | From Metaphor to Measurement: Resilience of What to What?[END_REF][START_REF] Klein | Resilience to natural hazards: How useful is this concept?[END_REF][START_REF] Davoudi | Resilience: A Bridging Concept or a Dead End? "Reframing" Resilience: Challenges for Planning Theory and Practice Interacting Traps: Resilience Assessment of a Pasture Management System in Northern Afghanistan Urban Resilience: What Does it Mean in Planning Practice? Resilience as a Useful Concept for Climate Change Adaptation? The Politics of Resilience for Planning: A Cautionary Note: Edited by Simin Davoudi and Libby Porter[END_REF], resilience has to address all territory components in order to analyze its risk reaction. However, the current understanding and operationalizing of the concept of resilience is 2 limited and remains an important issue which must be addressed. This research is principally divided into two approaches, a technical-functional approach and a more organizational approach [START_REF] Serre | DS3 Model Testing: Assessing Critical Infrastructure Network Flood Resilience at the Neighbourhood Scale[END_REF][START_REF] Serre | Assessing and Mapping Urban Resilience to Floods with Respect to Cascading Effects through Critical Infrastructure Networks[END_REF][START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF].

The technical-functional approach focuses on assessing the resilience of critical infrastructure, which concentrate all urban functions [START_REF] Escarameia | Technologies for Flood Protection of the Built Environment -Guidance based on findings from EU-funded project FloodProBE[END_REF][START_REF] Kunz | Investigation of superstorm Sandy 2012 in a multi-disciplinary approach[END_REF][START_REF] Pescaroli | How Critical Infrastructure Orients International Relief in Cascading Disasters[END_REF][START_REF] Pescaroli | Cascading Events, Technology and the Floods Directive: future challenges[END_REF] and their ability to withstand and recover from a disruption. These critical infrastructure are considered essential for the political territory well-being and territorial dynamics. It includes infrastructure such as telecommunication, energy transport networks, emergency services, critical buildings (hospitals, defense institutions, etc.), water and food supply, cyber or economic interactions, etc. Among these critical infrastructure, urban networks illustrate and concentrate several issues. In order to improve the resilience of cities, technical networks have already been identified as entry points for failures [START_REF] Serre | DS3 Model Testing: Assessing Critical Infrastructure Network Flood Resilience at the Neighbourhood Scale[END_REF][START_REF] Lhomme | Analyzing Resilience of Urban Networks: A Preliminary Step towards More Flood Resilient Cities[END_REF] and therefore constitute the systems on which technical and management measures will focus. Indeed, networks behave both as propagators of failure through their geographical extension and interdependencies, and are at the same time essential for reconstruction [START_REF] Serre | Advanced methodology for risk and vulnerability assessment of interdependency of critical infrastructure in respect to urban floods[END_REF]. Networks are thus the nervous system of the city in which the slightest failure can have significant consequences on the entire urban system [START_REF] Gonzva | Modeling disruptions causing domino effects in urban guided transport systems faced by flood hazards[END_REF]. Assessing the urban technical networks resilience therefore appears to be a critical step to increase cities' resilience, to guide the responses to reduce the effects of floods such as network improvements, evacuation recommendations, prioritization of interventions, etc. [START_REF] Robert | Réduire la vulnérabilité des infrastructures essentielles guide méthodologique[END_REF]: Macnally et al., 2007).

The organizational approach seeks to approach resilience from a more general analyse perspective than technical-functional resilience [START_REF] Toubin | Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services[END_REF][START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF]Heinzlef et al., 2020a). Resilience is a comprehensive and multidisciplinary approach that integrates many social and territorial elements, both tangible, such as critical infrastructure, buildings and so on, and intangible, such as cultural aspects [START_REF] Asprone | Urban network resilience analysis in case of earthquakes[END_REF]Heinzlef et al., 2019). Assessing the resilience potential of an organization or territory is necessary to mobilize managers in order to lead to the anticipation of disruptive events and the planning of management measures. The idea is to understand all the elements that promote resilience, namely, a better response from critical infrastructures, the built environment, managers, local actors and residents in order to cope with a disruption and restart an activity and a dynamic in response to it [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF].

The objective of this article is to present the methodologies and results coming from these two main approaches, namely the technical-functional and organizational approaches, leading to a clearer urban resilience operationalization . Faced with various limitations raised by current studies, this article proposes to develop the contribution of new techniques and research perspectives, in particular through the development of spatial decision support systems under the form of a Resilience Observatory. The first portion of this article presents the challenges of urban flood risks and the vulnerability of critical infrastructures. While the second and third portions describe different approaches based on the technical-functional analysis of resilience and the advantages and limits of organizational approaches, respectively. The final portion presents the perspectives of authors focused on the Resilience Observatory project in order to respond to the challenges of planning and decision-making processes in risk management strategies.

Vulnerable infrastructure: a critical issue for flood risk management

Urban areas concentrate economic, political, human, technical and urban challenges on increasingly limited geographical areas. Areas that are becoming increasingly vulnerable to the climate disasters. Among these urban areas, some infrastructure are more or less essential to the functioning of the territory. These critical infrastructure (CI) concentrate all the main functions which are necessary for the proper functioning of a territory [START_REF] Serre | Assessing and Mapping Urban Resilience to Floods with Respect to Cascading Effects through Critical Infrastructure Networks[END_REF]. These CI can represent systems, facilities, technologies, networks, assets and services essential to the health, safety, security or economic well-being of inhabitants and the effective functioning of government (Fig 1). [START_REF] Serre | Modelling Critical Infrastructure Network Interdependencies: A Preliminary Step to Designing Urban Resilience[END_REF] Critical infrastructure can be stand-alone or interconnected and interdependent. Most of these critical infrastructure interact, however, these interactions are often complex and unrecognized because they transcend the geographic, political, cultural and organizational boundaries of the systems [START_REF] Fekete | Critical Data Source; Tool or Even Infrastructure? Challenges of Geographic Information Systems and Remote Sensing for Disaster Risk Governance[END_REF]. For example, the fall of the World Trade Center towers in New York in 2001 caused, among other things, a breakdown of the web in South Africa, Germany, Italy and Romania. Disruptions of critical infrastructure could result in catastrophic loss of life, adverse economic effects and significant harm to public confidence. These interdependencies then play the role of a risk diffusion factor [START_REF] Lhomme | Analyzing Resilience of Urban Networks: A Preliminary Step towards More Flood Resilient Cities[END_REF]. According to the concept of the domino effects (Bach et al, 2013;[START_REF] Galland | Critique de la notion d'infrastructure critique[END_REF][START_REF] Nones | Implications of Cascading Effects for the EU Floods Directive[END_REF][START_REF] Pescaroli | Cascading Events, Technology and the Floods Directive: future challenges[END_REF], i.e. a chain reaction causing changes in a territory, some areas come to be impacted by the disaster, even if they were not located in the same area directly in the flood hazard extension zone. Among these CI, urban networks are a good example. In an interconnected world, urban networks connect more and more people and territories and offer a wide variety of resources and opportunities. However, they also create complex situations of interdependence. Public transport, electricity, gas, telephone, heating, waste, etc. make the management of the urban system more complex [START_REF] Serre | Assessing and Mapping Urban Resilience to Floods with Respect to Cascading Effects through Critical Infrastructure Networks[END_REF]. While they are essential for creating dynamics, relationships, economies, these networks are also extremely vulnerable in the event of a crisis. On account of their interconnectivity, all urban operations depend on them [START_REF] Serre | DS3 Model Testing: Assessing Critical Infrastructure Network Flood Resilience at the Neighbourhood Scale[END_REF]. A single failure can have cascading effects and disturb the entire network, and because of the reticular aspects of urban systems, the whole city [START_REF] Serre | Advanced methodology for risk and vulnerability assessment of interdependency of critical infrastructure in respect to urban floods[END_REF]. Therefore, some damages are not caused by direct physical damage, but by the interruption of activities supported by critical infrastructure (Heinzlef et al., 2020a). A distinction is made between direct and indirect impacts [START_REF] Nones | Implications of Cascading Effects for the EU Floods Directive[END_REF]. Direct impacts are directly caused by the disaster and may refer for example to damages to physical elements (furniture, buildings, stocks, equipment, etc.). Impacts become indirect when they are not caused by the disaster itself. Indirect impacts can be related to the interruption or damage of critical infrastructure service.

The dependencies of a city which relies on critical infrastructure increases the vulnerability of cities to risks aggravated by the emergence of "new" risks and uncertainties. To face such a challenge, risk management is beginning to evolve, especially in integrating the concept of resilience. As a concept with multiple interpretations, resilience remains complex to operationalize and integrate into risk management strategies, at least at local scales. Several methodological approaches have emerged in order to respond to these limits of appropriation. Among these approaches, critical infrastructure interdependencies were useful to first increase knowledge in this area.

This part is partly based on an approach we designed within a European FP7 project namely FloodProBE and described in this report [START_REF] Floodprobe | Identification and analysis of most vulnerable infrastructure in respect to floods. D 2.1 -Deliverable for Task 2[END_REF]: http://www.floodprobe.eu/partner/assets/documents/Floodprobe-Deliverable-Report_task21_4March2013.pdf

We invite the interested reader to read this report for a full presentation of the step wise approach we developed. Below we present only the most advanced step to integrate critical infrastructure networks interdependencies unpublished in scientific journals at this time. This corresponds to step 4 only of the figure 3.

Most critical infrastructure systems interact [START_REF] Peerenboom | Infrastructure interdependencies: Overview of concepts and terminology[END_REF] through direct connectivity, policies and procedures, or geospatial proximity [START_REF] Floodprobe | Identification and analysis of most vulnerable infrastructure in respect to floods. D 2.1 -Deliverable for Task 2[END_REF]. The modelling and analysis of interdependencies between critical infrastructure elements is a relatively new and very important field of study [START_REF] Pederson | Critical Infrastructure Interdependency Modeling: A Survey of U[END_REF]. It illustrates common representations of infrastructures based on the scenario of a flooding event and the subsequent response. There are ties and dependencies within each infrastructure and between the different sectors. The solid lines in crossing sectors and connecting nodes represent internal dependencies (Fig. 2), while the dashed lines represent dependencies that also exist between different infrastructures (infrastructure interdependencies) [START_REF] Floodprobe | Identification and analysis of most vulnerable infrastructure in respect to floods. D 2.1 -Deliverable for Task 2[END_REF]. [START_REF] Pederson | Critical Infrastructure Interdependency Modeling: A Survey of U[END_REF] The failure of one CI may cause disruption in others. For instance, the utility of traffic control in a municipality is generally provided by a system of three CIs -power grid, telecommunication network, and traffic control boxes. However, the proper functioning of the three CI system components is only a necessary condition for the normal operation of the traffic control system. It alone is not sufficient. The criteria for the connections between the three ICs, such as the nature and extent of their bonding or the self-regulating and management mechanisms, are essential elements for the proper functioning of the traffic control system, but only exist when the three ICs are interconnected [START_REF] Mcnally | Learning the critical infrastructure interdependencies through an ontologybased information system[END_REF].

CI can be considered as complex systems which can be defined as follows: ''Traditionally, a system is said to be complex if its attributes are commonly out of the norm, as compared with other systems. Complex systems are characterized by having a large number of dimensions, nonlinear or nonexistent models, strong interactions, unknown or inherently random plant parameters, time delays in the dynamical structure, etc.'' [START_REF] Jamshidi | Large-Scale Systems: Modeling and Control[END_REF]. Additional characteristics of complex systems are an adaptive emergent behavior and feedback loops.

CIs can be described as a ''system-of-systems''. 'A system-of-systems (SoS) consists of "multiple, heterogeneous, distributed, occasionally independently operating systems embedded in networks at multiple levels, which evolve over time' ' (DeLaurentis, 2003). Alternatively, system-of-systems can be defined using the term ''complex systems'': ''Systems-of-systems are large scale concurrent and distributed systems that are comprised of complex systems'' [START_REF] Kotov | Systems-of-systems as communicating structures[END_REF]. The questions are: how to deal with the complexity? And how to model such systems?

Consequently, it is important to draw distinctions between two related but different concepts -a CI system, and a system of CIs [START_REF] Hall | Systems-of-systems analysis of national infrastructure[END_REF]. A CI system is an assemblage of functional objects [START_REF] Fratini | Three Points Approach (3PA) for urban flood risk management: A tool to support climate change adaptation through transdisciplinarity and multifunctionality[END_REF]) that provides a certain essential good or service. A power supply system, for example, provides electrical service through the synergistic interactions among its components -the power plant, substations, transformers, and transmission and distribution lines. At the same time, a CI system is also a part of an even larger system -a system of CIs, which offers a range of public goods and services through the collaborative operations of (or interdependencies among) its individual CI system components. The behavior of a system of CIs, as a manifestation of the usually complex interdependencies, cannot be fully described and understood by the behaviors of its CI system components [START_REF] Rinaldi | Identifying, understanding, and analyzing critical infrastructure interdependencies[END_REF].

In the case of flooding [START_REF] Hoang | System interactions of stormwater management using sustainable urban drainage systems and green infrastructure[END_REF] it is essential for the functioning of the society to know where are the weak points in urban infrastructure networks [START_REF] Floodprobe | Identification and analysis of most vulnerable infrastructure in respect to floods. D 2.1 -Deliverable for Task 2[END_REF]. This knowledge is essential for flood risk management and mitigation measures. Some municipalities and other local governments are already well prepared and have a running flood risk management plan; others have not even started the dialogue between the many people and institutions which are responsible in the case of flood events. The stepwise approach provides a guide for risk assessment from a basic to an advanced assessment process (Fig. 3).

Figure 3: Framework for risk assessment (Lhomme et al.,2012) Starting with simple generic risk analyses, continuing with a computer based tool showing the weakest infrastructure asset in a municipality, including existing urban flood simulation and risk mapping and concluding with GIS based numerical model and risk mapping provides the framework support in the entire assessment process [START_REF] Floodprobe | Identification and analysis of most vulnerable infrastructure in respect to floods. D 2.1 -Deliverable for Task 2[END_REF]. The first two general approaches increase the awareness of the driving forces for flood risk management and mitigation.

Step three; flood risk mapping, previously referred to as the "classical" risk assessment methodology until today, is an essential input for step 4 which shows the interdependencies between critical infrastructures, the weak nodes in the system and subsystem, and the cascading effects. All four steps can be run independently. Indeed, these steps are adapted according to the risk data of the different municipalities. Depending on their knowledge, skills, advances, tools, the analysis can either implement the 4 steps or develop some of them according to the needs. These steps do not depend on a chronological order but on expressed and observed needs. Deciding which steps are required depends on the aim of the user and of the outcomes of the first steps. However, if the first steps show that there are CIs at risk from flooding, the latter two steps are needed to provide a full picture of the flood risks for CIs. It is an essential and crucial part, and its success mainly depends on the good will of the stakeholders. The last step can be difficult to understand and used by managers due to the over-technicality which complicates the urban managers' appropriation. Furthermore, an urban territory is composed by several components, integrating social dimensions (age of population, professional situation, habits, etc.), economic dynamics, land uses, etc.

Analyzing and understanding urban resilience needs to consider all these characteristics and elements in order to study the complexity of urban risks. Therefore, this primarily urban engineering approach must be processed with a more organizational and participative approaches to operationalize the concept of resilience (Heinzlef et al 2020a). To answer this issue, recent research on critical infrastructure interdependencies is taking three main directions:

-An engineering path leading to direct collaboration between experts and operators. This comes in the form of performance engineering, civil engineering and complex project engineering [START_REF] Robert | Réduire la vulnérabilité des infrastructures essentielles guide méthodologique[END_REF]; -The second path consists in developing collaborative approaches mixing modelling sciences and social sciences to better involve the majority of important stakeholders localized on specific territories [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF].

Finally, the methods we developed to model critical infrastructure networks interdependencies [START_REF] Lhomme | Analyzing Resilience of Urban Networks: A Preliminary Step towards More Flood Resilient Cities[END_REF] was a way to model the effects of flood propagation in cities as well as their consequences on a specific network and its cascading effects on others. Such a result is based on an urban complex analysis. Interested readers can consult [START_REF] Serre | Levee performance assessment: development of a GIS tool to support planning maintenance actions[END_REF][START_REF] Bambara | Developing a functional model for cities impacted by a natural hazard: application to a city affected by flooding[END_REF].

Achieving flood resilience through organizational answers: a more comprehensive approach

Faced with the limitations of a network-centric and technical-functional approach, a more global and comprehensive approach has been developed. This approach sought to address several pitfalls, namely the measurement and mapping of resilience, the visualization and understanding of the concept, and the appropriation of the concept by local stakeholders [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF].

Assessing resilience

A large part of operationalization consists in determining how a concept can be measured and selecting which indicators will be used to measure the concept in order to generate data about it [START_REF] Adger | New indicators of vulnerability and adaptive capacity[END_REF]. The assessment of resilience is therefore a matter of measurement and the designing of indicators [START_REF] Dauphiné | La résilience : un concept pour la gestion des risques[END_REF]. The use of indicators has spread in the field of risk, the measurement of territories and populations vulnerability, and resilience to risks. One of the first arguments to build indicators is that by defining and characterizing a fuzzy concept, indicators raise awareness of complex issues among the scientific community, as well as the general public [START_REF] Prior | Measuring Resilience: Methodological and Political Challenges of a Trend Security Concept[END_REF]. Furthermore, resilience indicators can make major contributions to assessing community needs and objectives while aiding to set up resilience strategies [START_REF] Cutter | The Landscape of Disaster Resilience Indicators in the USA[END_REF]. By providing information on the territory, the risks and the level of resilience, these indicators make it possible to build new knowledge by raising the awareness of the populations and by accompanying the actors towards a transition towards more resilient risk management. These indicators, which are useful when designing a strategy, are also valuable for monitoring the progress of work, decision-making and progress made by a community. Measuring resilience has therefore become an international priority in order to build strategies to risk management [START_REF] Winderl | Disaster Resilience Measurements[END_REF]. The question of how resilience is measured is as old and important as the concept itself [START_REF] Prior | Measuring Resilience: Methodological and Political Challenges of a Trend Security Concept[END_REF]. Numerous indices and indicators of resilience have been developed in various disciplines (Freudenberg,2003). While some research has established global indicators (physical, economical and social indicators) on a national scale, others have favored a local scale at the infrastructure level by focusing on technical-functional indicators. Few researches have managed to reconcile the issue of decision support with a comprehensive approach to the concept of "local" infrastructure (Cuter et al., 2010).

In this context of organizational resilience, we developed three indicators in order to measure urban, technical and social resilience at a local urban scale [START_REF] Serre | Assessing and Mapping Urban Resilience to Floods with Respect to Cascading Effects through Critical Infrastructure Networks[END_REF].

To address the issue of risks in urban areas, the choice was made to analyze resilience over a long period of time (before, during and after a crisis), and no longer by only following a shock [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF]. This article has made it possible to understand the determining components useful for a resilience strategy design. This positioning has allowed for a deeper, more thorough conceptual framework for resilience. Thanks to the identification of these components, three indicators were designed as below (Fig 4 .): • An urban resilience indicator: urban resilience embraces all urban dynamics -physical such as buildings (age of the building, elevation,… for example) and critical infrastructure -or virtual such as economic dynamics. We have analyzed the influence zones of critical infrastructure within a 100m radius, access to medical infrastructure (in ten minutes), tourism and economic dynamics (business creation and disappearance) ;

• A social resilience indicator: social resilience is defined here as the ability of a population to adapt and recover from a disturbance. Several factors enable a population to act proactively, react and redevelop activities and interactions during and after a crisis. These factors may include age (calculation made, for example, on the ratio of the elderly to the total population), socio-economic status, education level, habits, government support, etc. In this analysis, social resilience is approached as a community resilience, not individual resilience; • A technical resilience indicator: as previously established, urban networks are essential in the analysis of resilience. In this analysis, we integrate both the diversity of networks (the number of different networks within a 100 m radius and the accessibility of these networks (the length in meters of public roads to access these networks in the area).

The data for each indicator was 90% open source. After selecting the raw data, the data was transformed and normalized. In order to understand the frequency of each variable, each raw data item was transformed into percentages (Heinzlef et al., 2020). Each variable had a weight of 1. This unique weighting is explained by the desire to avoid disparities between variables [START_REF] Fekete | Validation of a social vulnerability index in context to river-floods in Germany[END_REF], as some of them are sensitive and subjective. Following this process, it was necessary to determine the normalization. Normalization allows a series of values (usually representing a set of measures) to be adjusted according to a transformation function in order to make them comparable at specific reference points. A min-max normalization was performed to illustrate variable which have a positive resilience impact (such as working people and young people) and variable which have a negative resilience impact (such as the very old or very young), where each variable is decomposed into an identical range between zero (worst rank) and 1 (best rank), to create indicators with similar measurement scales, and to compare them with the same set of measures. (Heinzlef et al., 2020). This research answered the local challenges of defining and measuring resilience [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF]. This research has been developed, tested and applied on the city of Avignon (France). A collaborative approach has enabled the results of the indicators to be put in place and led to long-term thinking to implement resilient risk management strategies. As the research had previously focused on technical-functional resilience, this part allows for the understanding of resilience through a more exhaustive prism including urban, social and technical characteristics in order to analyze territorial resilience in all its complexity. The challenge now is to work on the accessibility of these indicators in order to make them understandable, usable and reusable by different local actors in order to be able to produce a broader resilience index [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF].

Mapping and visualizing resilience

Faced with a lack of integration of resilience models in risk management plans, we looked for a possible approach where the concept of resilience could better integrate future plans. After having constructed a conceptual model of resilience and three measurement indicators, it was decided to use geo-visualization techniques to operationalize the resilience concept [START_REF] Kwan | Geovisualization of Human Activity Patterns Using 3D GIS: A Time-Geographic Approach[END_REF][START_REF] Marzouki | The Relevance of Geovisualization in Citizen Participation Processes[END_REF][START_REF] Kurwakumire | Geographic Information and Geo-Visualisation in Support of Disaster Resilience[END_REF]. Geo-visualization techniques group together visualization practices, mapping, data analysis and production, etc. in order to participate in decision-making [START_REF] Nöllenburg | Geographic Visualization[END_REF]. The processing tool (Feature Manipulation Engine) uses an interface instead of code lines, which makes the computer script more accessible and understandable (Heinzlef et al., 2020a). In addition, the accessibility, updating and reuse of data is promoted by 90% use of open access data (National Institute of Statistics and Economic Studies) (Heinzlef et al., 2020a). This willingness to "transmit" research beyond the study itself was reflected in the choice of open data and open access tools. In addition, this willingness to promote the results is explained by the fact that urban managers do not fully understand how to use the concept of resilience in their plans [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF]. Using known, free and accessible data helps to promote understanding and use of the established methodology. Open data and open access tools "liberate" knowledge and construct knowledge [START_REF] Goëta | L'open data peut-il (encore) servir les citoyens ?[END_REF][START_REF] Janssen | Benefits, Adoption Barriers and Myths of Open Data and OpenGovernment[END_REF]. The interest of the method is expressed by the local scale modelling of the elements of urban, technical and social resilience, and the collaborative approach with local actors. (Heinzlef et al., 2019). This collaboration did not take place a posteriori to the design of the spatial decision support system but at each stage. Moreover, each step of the script, data used and results are easily understandable and accessible thanks to the choice of tools and data.

Most models do not make their processing or databases accessible. Resilience is also limited to a technical-functional analysis by integrating the impacts of domino effects. This research led to designing a spatial decision support system that enables the visualization, understanding and accessibility of treatments and results for local stakeholders (Heinzlef et al., 2019;[START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF]. The design was carried out in collaboration, allowing local actors to integrate the methodology, but also to share their expertise. The spatial decisionsupport system makes it possible to assess and map urban, technical, social and environmental resilience.

The challenge now consists in making these models accessible by changing the scales of analysis and the study area (sub-district, neighbourhood, city, networks, etc.). The idea is to think about a tool that allows for the confrontation of different scales thanks to a visualization that is easy and accessible for local actors.

Operationalize the concept of resilience through collaborative approaches

Involving "local" people or people directly concerned by the issues studied does not seem to be new and even less original [START_REF] Toubin | Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services[END_REF]. The richness of having people from all walks of life interact allows for "exploring the world of possibilities" [START_REF] Callon | Agir dans un monde incertain: essai sur la démocratie technique[END_REF], enriching discussions, encouraging cross-fertilization of views on the same subject, to be both more measured and more incisive in a specific field. Resilience, a social and tricky concept, is therefore a subject that requires a confrontation of views, knowledge, scientific and practical knowledge, perceptions and interpretations. Nevertheless, despite the population being often the first impacted by natural hazards and their difficult management, the inhabitants [START_REF] Kuhlicke | Perspectives on Social Capacity Building for Natural Hazards: Outlining an Emerging Field of Research and Practice in Europe[END_REF] as well as the urban services (Toubin et al.2015), which are nonetheless actors most directly impacted, are not sufficiently involved. We defend the idea that the conception of a hybrid knowledge allowing the involvement of all actors of the territory, from inhabitants to managers via scientists and or facilitators, would allow the operationalization of urban resilience thanks to an appropriation of the concept and stakes of urban risks [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF].

It would therefore be beneficial to build this shared vision and commitment around the concept of resilience, an approach that would also allow a transition in the ways of conceiving the city and understanding risks in urban environments [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF]. We therefore propose to develop strategies for integrating resilience in a co-designed manner with city's stakeholders. This would allow their direct involvement, as well as the application of this strategy before or during a crisis [START_REF] Serre | Modelling Critical Infrastructure Network Interdependencies: A Preliminary Step to Designing Urban Resilience[END_REF]. Involvement at the level of conception may guarantee the sustainable use of the resilience concept in flood risk management strategies [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF]. 4.3.1. Parisian case study [START_REF] Toubin | Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services[END_REF] developed a methodology to contribute to improving conditions of urban resilience and more particularly resilience of Parisian urban networks face to urban floods, based on the 1910 case study. Indeed, the Paris conurbation is exposed to the risk of major but infrequent floods. The inevitable occurrence of flooding is all the more worrying for the authorities as they see other major world cities hit hard, sometimes a few years apart, by similar events (New York or Prague, for example). The flood of 1910 is the focus of attention because it is rich in lessons for the modern Paris that was already taking shape at the time. It is also interesting to note that Paris' status as a world city (embodied notably by the 1900 Universal Exhibition) was not called into question after the 1910 flood. However prospective studies show that such a flood today would be much more critical for the metropolis with its major economic and political stakes, supported by complex urban services. This analysis of interactions and interdependencies of urban networks allowed highlighting intrinsic fragilities of urban systems and their management in the event of a crisis [START_REF] Toubin | An auto-diagnosis to highlight interdependencies between urban systems[END_REF]. In the context of the issues observed, the objective of the research was therefore to develop approaches and tools to help urban service managers to identify and implement the most appropriate characterize technical and organizational interdependencies to ensure the continuity of service despite disruption propagations in such critical infrastructure networks. The approach was built by integrating urban managers of the services areas of the City of Paris. This research draws up and analyzes the interdependencies of Parisian urban networks. It highlights certain dependencies, particularly those on electricity, telecommunications and transportation. The collaborative approach involved managers and forced them to think about strategies to mitigate or at least manage these interdependencies together. In addition, the collaborative process illustrated the need to move beyond isolated approaches (Fig. 5) but rather to foster a common vision [START_REF] Toubin | Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services[END_REF]. The collaborative approach can, for example, be used to illustrate the interdependencies between networks (Fig. 5), the compartmentalized risk management between public and private actors in the city's services (Fig. 5), and shed light on the major obstacles to the implementation of adaptation of the urban system to improve its overall resilience. The interweaving of scales as well of services, makes cooperation and transparency between operators and decision-makers indispensable for the construction of a more resilient city [START_REF] Toubin | Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services[END_REF].

Avignon case study

Seeking to analyze resilience through the three measurement indicators previously identified, a study in Avignon put forward the collaborative approach from a more exhaustive angle [START_REF] Serre | Assessing and Mapping Urban Resilience to Floods with Respect to Cascading Effects through Critical Infrastructure Networks[END_REF]. The approach developed emphasized collaboration between scientific experts and local actors. Building a common approach has made it possible to clarify the concept of resilience and translate it into a risk management strategy. This collaboration was carried out with the GIS service of the city of Avignon.

The collaboration crystallized at several stages of the research [START_REF] Heinzlef | Operating urban resilience strategies to face climate change and associated risks: some advances from theory to application in Canada and France[END_REF]. After an analysis of the concept of resilience via a study of the scientific literature, a confrontation between scientific positioning and the knowledge of local actors took place. Indeed, it was necessary to reassess the envisaged indicators in light of the data used by the GIS department. After establishing the conceptual model of resilience with the indicators, the choice of processing tools was based on those used and known by the actors. The data processing and analysis was carried out at a regular frequency with the GIS department. As the spatial decision-support system is being built, a number of meetings with managers of critical infrastructures were held to test and validate the results. Thus, each stage was confronted with the reality of the actors, their understanding and their future use of the tool. This collaborative approach questioned the operationalization of the resilience and proposed an approach to meet these challenges. It appeared necessary to involve local knowledge, habits and practices in the construction of the tool to ensure its usefulness and subsequent use [START_REF] Vanderlinden | Coastal Flooding, Uncertainty and Climate Change: Science as a Solution to (Mis) Perceptions? A Qualitative Enquiry in Three Coastal European Settings[END_REF]. Collaborative strategies allow for a common knowledge to be built around a complex concept. This allows fuzzy concepts to be debated, dissected and operationalized. A spatial decision support system was designed with and for urban managers [START_REF] Heinzlef | Operationalizing urban resilience to floods in embanked territories -Application in Avignon, Provence Alpes Côte d'azur region[END_REF]. The challenge is to deepen this collaborative dimension by offering a platform for meetings, exchanges and local scientific-expert collaboration in order to promote the operationalization of resilience in risk management strategies.

These previous studies have helped to address some of the challenges of operationalizing resilience. Nevertheless, the obvious weakness of these studies is its multitude and the difficulty of local actors to integrate and understand it easily. The objective of this long-term work on the integration of the concept of resilience into risk management strategies is to envisage a living laboratory and an Information System Software structure that would bring together advances in the field and provide support for awkward resilience strategies and technical advances for scientists and local experts.

An observatory design: a long term and inclusive resilience monitoring and planning

The operationalization of resilience faces two major limitations:

• the difficult understanding of the concept itself;

• its application to the risk management dimension.

The challenge of integrating resilience into risk management is part of a complex and constantly evolving context: climate change and associated uncertainties. Faced with this climatic context, and with political, social, economic and territorial elements that evolve, there is an ever-increasing need for understanding and observation [START_REF] Serre | Observatories, long term resilience monitoring, a review[END_REF][START_REF] Heinzlef | Thinking urban flood resilience through observatory design[END_REF]. It is therefore a question of understanding territorial systems in all their complexity by bringing together data and information produced by and for stakeholders. As a result, local actors are able to come together around issues that will require the implementation of development or management actions.

Observatories are tools whose objective is to observe (monitor, analyze, understand) on a portion of space representative of a territorial entity, the socio-environmental dynamics resulting from dynamic interactions of socio-economic and biophysical systems. They are a place of production, exchange, and sharing of information and knowledge that is sustainable. Observatories, at the interface between complex reality and knowledge (de Sède-Marceau and Moine, 2012), are therefore effective decision-making tools [START_REF] Gayte | Conception des systèmes d'information sur l'environnement[END_REF]Heinzlef and Serre, 2020). Territorial dynamics and structures are changing very rapidly, due to political, environmental, demographic [START_REF] Montgomery | The Urban Transformation of the Developing World[END_REF], spatial, organizational, governance [START_REF] Mendizabal | Stimulating urban transition and transformation to achieve sustainable and resilient cities[END_REF] transformations and other factors. These rapid changes lead to a growing need for information and observation in order to understand these complex territorial systems (de [START_REF] De Sède-Marceau | Développement d'observatoires territoriaux, entre complexité et pragmatisme[END_REF]. Observatories are therefore beneficial tools for understanding, decision support tools for planners and elected officials, and a place for producing, exchanging and sharing information and knowledge over the long term (Heinzlef and Serre, 2020). To support territorial management, this observatory has to provide diagnostic functions to perform the evaluation of implemented actions. For instance, it may help to have a global perception of different issues on an urban project to measure positive and negative impacts on flood risk territories. It should also be associated with prognostic functions, in order to have the capacity to alert and guide managers in their decision-making process in the short and medium term. In addition, spatial decision support tools are often dependent on a specific territory and actors. An observatory is a spatial decision support tool on a larger scale, which can compare and confront several case studies, actors, experts, methodologies. There are currently various active observatories dedicated to the observation of the territory and space phenomena. They exist in the form of a virtual structure such as for the National Observatory of Natural Risks and the Territorial Observatory, etc. Their objective is to gather, analyze and disseminate data relating to territorial dynamics and disparities, and to allow everyone, professionals and individuals, to easily access data relating to natural risks produced by organizations for a better understanding of these phenomena and their impacts. However, these observatories combine neither scientific advances nor local knowledge, do not propose a double entity (virtual structure + living laboratory), and stop at the data acquisition part.

The future observatory would be a toolbox; developing, refining, and applying various methodologies to operationalize resilience. Initially conceived as a spatial decision support system, an evolution towards a living laboratory would be an essential transition. Composed of a university team and local actors, the human dimension of the observatory could enable in situ testing of resilience strategies and foster collaborative approaches (Fig. 6). A test site will therefore be chosen according to the issues related to risks, and will serve as a crucible for innovation and as a prototype observatory. It is then a necessity to develop an observatory for reflection and action around the concept of resilience in the face of risk management. It is one important step to prepare territories, populations and local actors for climate disruption.

Increasing risk knowledge

The primary objective of this observatory is to produce, condense, multiply and transmit knowledge on risks and resilience. To this end, defining and assessing resilience at the local level is required in order to drive a decision support process. This step is built on previous research on the design of resilience indicators dealing with, urban, social and technical aspects. The challenge is to make them generic and reusable on different case studies and for various local actors in various contexts. The objective is to develop and deepen the preexisting indicators in order to nuance the analysis with, in particular, a governance indicator (community investment of populations, action policies, dissemination of information concerning risks, land use planning policies, risk management, etc.).

Collecting data and mapping

Beyond enhancing the value of pre-existing open-access data, the observatory would be a key tool for producing new forms of data. Tools such as UAVs (Unmanned Aerial Vehicle) would contribute to improving knowledge on territories at risk in a very precise manner and in particular to define the adaptive potential of these territories. Moreover, the data acquired via UAVs would be processed by the Resilience Observatory and could provide a valuable decision-making aid for many decision-makers.

The interest of UAVs in risk management is manifold. Their low-cost use ensures the widespread adoption of these tools [START_REF] Serre | Observatories, long term resilience monitoring, a review[END_REF]. In addition, the automation of the tool can allow a repeatability of measurement which would be valuable in the monitoring of space evolutions leading to a more accurate and complete spatio-temporal monitoring. Finally, such tools are advantageous for accessing territories that are difficult for individuals to access. In addition to data acquisition, data processing and visualization will be an important area of development, particularly with geo-visualization techniques.

Resilience Observatory

Interactions Interactions Living Laboratory

Engaging stakeholders

Since the 1990s, there has been a growing interest in the geospatial dimension of data, particularly in reason of the dissemination of geographic information systems and technologies [START_REF] Andrienko | Geovisual analytics for spatial decision support: Setting the research agenda[END_REF]. These technologies include geographic information systems (GIS), low-cost GPS equipment and satellite imagery, among others [START_REF] Appeaning Addo | Drone as a tool for coastal flood monitoring in the Volta Delta, Ghana[END_REF]. Recently, software for the collection, storage and analysis of geo-referenced information is becoming increasingly user-friendly. Thus, development practitioners, activists and researchers are turning to GIS to increase the participation of local people in planning processes at the local or regional level, and to facilitate the dialogue between policymakers and communities on the ownership, use and control of natural resources. As a result, a growing number of community-based initiatives are emerging to collect, organize, visualize and geo-reference the knowledge of local people using what is generally referred to as participatory GIS. Participatory GIS is actually an approach born out of the combination of participatory learning and action methods and traditional GIS. It is based on the integrated use of tools, methods, technologies and systems ranging from simple map sketches to participatory three-dimensional modelling, common interpretation of aerial photos and the use of GPS and various GIS applications. Through participatory GIS, local people's knowledge is translated into two-or three-dimensional, physical, open-access maps and used as interactive tools for geospatial learning, information exchange, decision support, natural resource use planning and advocacy.

The observatory would therefore integrate a kind of participatory GIS for local actors to promote understanding (van de [START_REF] Van De Ven | Adaptation Planning Support Toolbox: Measurable performance information based tools for co-creation of resilient, ecosystem-based urban plans with urban designers, decisionmakers and stakeholders[END_REF], perception and integration of the concept of resilience into risk management strategies.

5.4.A Pacific resilience observatory

A research project led by the IRD and the CNRS has been set up in order to respond to the challenges of operationalizing resilience in French Polynesia. The objective of this Pacific Island Long Term reSilience (ILOTS) project is to initiate reflection on a Resilience Observatory in order to work on the limits and biases of the concept and its operationalization (Serre, 2019). Building a Resilience Observatory prototype in the Pacific islands makes sense in light of the risks to which they are exposed. The French overseas islands have a high level of hydrometeorological hazards and often inadequate risk management methods, tools and strategies. A 2014 interministerial report also highlights the difficultly of sharing responsibilities between national and local authorities with regard to poor risk management processes, with one crucial point in particular: the national risk observatory does not cover the overseas territories. At the same time, local authorities do not seem to be willing to fully engage in risk management, with the exception of hurricane-related issues, due to the cultural awareness of the population in the face of these hazards. A more critical problem is the lack of control of land and urban development by local authorities. The report also contains recommendations to improve risk management strategies in overseas regions such as the ambition to transform overseas territories into territories of innovation for risk management by engaging the scientific communities and to make urban planning a non-structural measure to reduce risks by taking into greater account of the impacts of climate change.

The observatory project will therefore make it possible to design a framework to meet the needs in terms of scientific, technical, social and territorial advances. Thus, the observatory prototype is innovative at several levels; responding to an assessed need (intensity and recurrence of disasters) with a solution that does not yet exist, carrying out the observatory with new models to assess the level of resilience to floods in a multi-scale perspective (space and time) and using open source tools, data and solutions as much as possible in order to minimize the cost of the observatory and maximize its future use. This observatory project would therefore be justified from an economic point of view. The emphasis on open source tools and the use of existing data that is not very valuable or not cross-referenced in an enriching way to operationalize resilience makes the cost of the tool almost non-existent for local actors. The current costs are linked to the research teams but only financed by the scientific projects of the academic team. Subsequently, it will be a question of training local actors in the use of the tool. For these reasons, a prototype toolbox such as an observatory takes on its full meaning in the pacific island territories.

Conclusion

Faced with the challenges of climate change and the uncertainties related to risk management, the concept of resilience has emerged as an innovative and promising way to prepare territories, populations and territorial actors. However, this concept is still unclear and difficult for local actors to understand and operationalize.

This article highlights two methodologies aimed at addressing the limitations of integrating the concept of resilience into risk management strategies: a technical-functional methodology and a more organizational one. The technical approach has the advantage of responding to critical infrastructure issues and interdependencies that increase territorial vulnerability. However, this approach is limited because it reduces territorial complexity to critical infrastructures. The organizational approach tends to respond to these limitations by proposing to analyze the different elements that make up the territory and participate in increasing and/or reducing resilience. While these two approaches make it possible to advance in the clarification and use of the concept by local stakeholders, the multitude of tools, their temporal limitation of use and their very localized action make these methodologies limited and too localized.

On account of this observation, a global tool project has been envisaged; a resilience observatory. A resilience observatory would make it possible to develop a comprehensive human and computer-based tool to condense, compare, develop and bring out different methodologies for operationalizing resilience. Based on several pillars (defining and measuring resilience, acquiring, processing and visualizing data, promoting and developing the integration of local stakeholders in the process of cultivating resilience, etc.), the observatory would make it possible to reconcile local, international and scientific advances in order to provide a structure for reflection and action to operationalize resilience. In addition, such a structure would make it possible to develop tools and methodologies that address resilience in a comprehensive and exhaustive way, but also over a long period of time. Indeed, the monitoring, acquisition and use of past and current data would make it possible to apprehend the territory, the risks and the resilience over the long term in order to adapt risk management strategies in the face of a spatial but also social trend. This temporal dimension is essential in order to allow appropriation, to consider the concept of resilience and to promote decision support. Such a prototype has been launched and tested in the Pacific and more particularly in French Polynesia in order to serve as a reference case study to develop this kind of observatory on an international scale in the future.

Figure 1 .

 1 Figure 1. Critical infrastructure network as a support of urban life[START_REF] Serre | Modelling Critical Infrastructure Network Interdependencies: A Preliminary Step to Designing Urban Resilience[END_REF]

Figure 2 :

 2 Figure 2: Critical infrastructure interdependency modelling[START_REF] Pederson | Critical Infrastructure Interdependency Modeling: A Survey of U[END_REF]

Figure 4 :

 4 Figure 4: Resilience characteristics(Serre and Heinlef, 2018)

Figure 5 .

 5 Figure 5. From individual operator resilience infrastructure diagnosis to interdependency mapping for risk management

Figure 6 :

 6 Figure 6: A prototype observatory

Modelling critical infrastructure networks interdependencies: a partial view of urban resilience

Acknowledgement

This research has been supported by the region Provence-Alpes-Côte d'Azur (grant no. 2016_11877). This project has received financial support from the CNRS through the MITI interdisciplinary programs and from the IRD.


Marjolaine Le Gac

Clément Ferrier

Cyril Touboul

Clémentine Owen

Alexandra Arfi

Anne-Sophie Boudy

Aude Jayot

Sofiane Bendifallah

Professor Emile Daraï
email: emile.darai@aphp.fr

Comparison of robotic versus conventional laparoscopy for the treatment of colorectal endometriosis: Pilot study of an expert center

Keywords: Endometriosis, Colorectal endometriosis, Laparoscopy, Robotic surgical procedures

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Endometriosis is a chronic disease, characterised by the presence of glands and endometrial stroma outside the uterus, affecting up to 10% of women 1 2 3 . Deep endometriosis (DE) is defined by the infiltration of anatomical structures and organs beneath the peritoneal surface by endometriotic tissue. DE with colorectal involvement is considered one of the most severe and complex form with an impact on the quality of life and fertility 4 5 .

The rectum and the rectosigmoid junction are the most common locations representing over 80% of all bowel endometriosis 6 7 . Surgical management of DE with colorectal involvement remains an option after failure of medical treatments [START_REF] Daraï | Randomized trial of laparoscopically assisted versus open colorectal resection for endometriosis: morbidity, symptoms, quality of life, and fertility[END_REF][START_REF] Roman | Baseline severe constipation negatively impacts functional outcomes of surgery for deep endometriosis infiltrating the rectum: Results of the ENDORE randomized trial[END_REF][START_REF] Nezhat | Robotic-assisted laparoscopy in gynecological surgery[END_REF] . Colorectal resection for endometriosis has demonstrated its efficacy on gynecological, digestive and urinary symptoms, fertility, as well as on quality of life 8 9 . However, colorectal resection expose patients to the risk of severe complications such as rectovaginal fistula, anastomotic dehiscence, pelvic abscess and voiding dysfunction imposing a share making decision with the patients according to their priorities [START_REF] Nezhat | Robotic versus standard laparoscopy for the treatment of endometriosis[END_REF][START_REF] Chammas | Asymptomatic rectal and bladder endometriosis: a case for robotic-assisted surgery[END_REF][START_REF] Bazot | Deep pelvic endometriosis: MR imaging for diagnosis and prediction of extension of disease[END_REF][START_REF] Bazot | Diagnostic accuracy of physical examination, transvaginal sonography, rectal endoscopic sonography, and magnetic resonance imaging to diagnose deep infiltrating endometriosis[END_REF][START_REF] Daraï | Laparoscopic versus laparotomic radical en bloc hysterectomy and colorectal resection for endometriosis[END_REF][START_REF] Jayot | Comparison of Laparoscopic Discoid Resection and Segmental Resection for Colorectal Endometriosis Using a Propensity Score Matching Analysis[END_REF][START_REF] Jayot | Comparison of Laparoscopic Discoid Resection and Segmental Resection for Colorectal Endometriosis Using a Propensity Score Matching Analysis[END_REF] .

Conventional laparoscopy is currently considered the standard for endometriosis colorectal resection thanks to its advantages on intra and postoperative complications, hospital stay and short recovery compared to open surgery [START_REF] Gala | Systematic review of robotic surgery in gynecology: robotic techniques compared with laparoscopy and laparotomy[END_REF][START_REF] Vesale | Rectovaginal fistula prevention after enbloc colorectal resection and hysterectomy for deep endometriosis[END_REF][START_REF]Omentoplasty is effective in lowering the complications of ano-rectal resections[END_REF][START_REF] Haas | The rASRM score and the Enzian classification for endometriosis: their strengths and weaknesses[END_REF] . Recently, assisted-robotic laparoscopy emerged as an alternative to conventional laparoscopy although its superiority remains questionable in gynecological surgery [START_REF] Nezhat | Robotic-assisted laparoscopy in gynecological surgery[END_REF][START_REF] Gala | Systematic review of robotic surgery in gynecology: robotic techniques compared with laparoscopy and laparotomy[END_REF] . In the specific setting of colorectal endometriosis, few small studies and case reports have been published to compare assistedrobotic to conventional laparoscopy 12 13 . Therefore, the aims of the present pilot study from an expert center in endometriosis were to evaluate and to compare safety, intra and postoperative complications and short postoperative outcomes of robotic to conventional laparoscopy for endometriosis colorectal resection on a series of 48 patients operated on the short period of 6 months.

MATERIEL AND METHODS

From March 2019 to September 2019, we conducted a prospective cohort study of patients undergoing a colorectal resection for endometriosis at Tenon University Hospital, Expert Centre in Endometriosis (CE), Groupe de Recherche Clinique in endometriosis Sorbonne University (GRC-6 SU), Paris, France.

Patients

The inclusion criteria were patients over 18 years-old, after failure of medical treatment or with infertility; with a preoperative diagnosis of DE with colorectal involvement confirmed by transvaginal ultrasonography, magnetic resonance imaging (MRI), and rectal echo endoscopy (REE) using previously published criteria [START_REF] Bazot | Deep pelvic endometriosis: MR imaging for diagnosis and prediction of extension of disease[END_REF][START_REF] Bazot | Diagnostic accuracy of physical examination, transvaginal sonography, rectal endoscopic sonography, and magnetic resonance imaging to diagnose deep infiltrating endometriosis[END_REF] , schedule for colorectal resection. Patients with DE without proved colorectal endometriosis or requiring an Assisted Reproductive Technique (ART) and refusing bowel surgery were excluded of the study.

Patients with prior colorectal surgery were also excluded.

Surgical Procedure

In February 2019, the hospital was equipped with the da Vinci Surgical System Si (Intuitive Surgery). The two surgeons began to perform colorectal procedures in March 2019, after being trained specifically in robotic surgery, between September 2018 and February 2019. The surgeons specific-procedure (conventional laparoscopy for rectal endometriosis) volume per year is 40-50 cases.

During the study period, the interventions were either performed by robotic or conventional laparoscopy depending on availability of robotic room without criterion to select patients according to the extent of the lesions neither prior surgery for endometriosis as the surgery was planned one year ago.

The surgery was performed under general anesthesia. An indwelling urinary catheter was placed and an intrauterine manipulator. For robotic surgery, an umbilical incision was done to create a pneumoperitoneum using a Veress needle. Then an 8 mm umbilical trocar was placed for endoscope. On the same horizontal line, a 12 mm trocar was placed at the right side for harmonic scapel or automatic stapler and an additional 8 mm trocar on right flank for grasping forceps. On the left side an 8 mm trocar was placed for bipolar forceps and an additional classic 5 mm trocar for suction/irrigator device. For conventional laparoscopy, surgery was performed as previously described [START_REF] Daraï | Laparoscopic versus laparotomic radical en bloc hysterectomy and colorectal resection for endometriosis[END_REF] .

All the robotic and conventional laparoscopic colorectal resections were performed by surgeons (ED, SB) with an experience of at least 150 laparoscopic colorectal resections. All the robotic and conventional laparoscopic colorectal resections were performed with the objective of complete resection, as previously described [START_REF] Daraï | Laparoscopic versus laparotomic radical en bloc hysterectomy and colorectal resection for endometriosis[END_REF][START_REF] Jayot | Comparison of Laparoscopic Discoid Resection and Segmental Resection for Colorectal Endometriosis Using a Propensity Score Matching Analysis[END_REF] . Procedures included adnexal surgery (ovarian cystectomy or salpingo-oophorectomy), uterosacral ligament, torus uterinum, parametrium, partial colpectomy, hysterectomy, ureterolysis; and ureteral reimplantation when required. The first step of the surgery consisted in exploring the abdomen, mobilizing the colorectum to evaluate the size and extension of the bowel endometriosis, identifying critical structures, and determining whether it was multicentric or multifocal. For segmental resection, the ureter was identified crossing the pelvic brim and mobilization was continued inferiorly to open the pararectal space. The mesocolon was then opened and dissection extended down to the pararectal space. The space posterior to the rectosigmoid mesocolon was opened. During this dissection the anterior branches of the hypogastric plexus were identified, allowing a nerve-sparing surgery.

Depending on the evaluation of the size and extension of the bowel endometriosis, three types of colorectal resection could be performed: rectal shaving, discoid excision or segmental resection. Rectal shaving was performed for lesions with superficial serosal rectal infiltration. A discoid excision was performed for lesions infiltrating the rectal muscularis less or equal to 3 cm in length and involving less than 90° of the bowel circumference. Performed either by standard laparoscopy or robotic surgery, the steps of a discoid excision procedure were identical. Segmental resection was performed for colorectal endometriosis over 3 cm or involving more than 90° of the bowel circumference or for multifocal lesions [START_REF] Jayot | Comparison of Laparoscopic Discoid Resection and Segmental Resection for Colorectal Endometriosis Using a Propensity Score Matching Analysis[END_REF] . Segmental resections require a laparotomy step. The bowel is extracted through a supra-pubic minilaparotomy incision, and resected. Then, a purse is created for the anvil and the colon is reintroduced inside the peritoneal cavity before closing the supra-pubic incision. Rectal anastomosis was performed by introducing an automatic stapler in the rectum. Except for the skin incisions, trocars localization and the docking procedure in the robotic group, the surgical steps were identical either performed by robotic or conventional laparoscopy.

Indication of laparotomic conversion were technical difficulties or major intraoperative complication. The creation of ileostomy was performed for patients requiring partial colpectomy when interposition of prevesical peritoneal was not feasible [START_REF] Vesale | Rectovaginal fistula prevention after enbloc colorectal resection and hysterectomy for deep endometriosis[END_REF][START_REF]Omentoplasty is effective in lowering the complications of ano-rectal resections[END_REF] .

Colorectal endometriosis was histologically confirmed in all the patients.

Statistical analysis

The following patient characteristics were recorded: age, body mass index (BMI), parity, previous surgery, details of surgical procedure performed and preoperative symptoms.

The American Society for Reproductive Medicine score and Enzian score were systematically calculated [START_REF] Haas | The rASRM score and the Enzian classification for endometriosis: their strengths and weaknesses[END_REF] .

Postoperative complications were classified according to the Dindo-Clavien classification system as minor (grade I-II) or major (grade IIIA and IIIB-IV), and compared between the two surgical groups. Voiding dysfunction was defined by the need of intermittent bladder self-catheterization when postvoid residual urine volume was greater than 100 millilitres.

Persistent voiding dysfunction is defined by urinary dysfunction lasting more than 1 month.

The population was divided into two groups according to the surgical route i.e. robotic or conventional laparoscopy group.

Univariate analysis was performed using the Student's t test for normally distributed data and Chi Square test for categorical data were used the Wilcoxon test for continuous variables and the Fisher exact test for categorical variables. All reported p values were 2-sided.

Significant difference was denoted when p<05. All statistical analysis was performed using commercially available software (Stata/IC 14.0).

10

RESULTS

Epidemiologic characteristics of the study population

During the study period, 48 patients were included, 25 in the conventional laparoscopy group and 23 in the robotic group.

No difference was found in epidemiologic characteristics between the groups Table 1.

The mean age was 36 ± 7 years in the robotic group and 37 ± 8 years in the conventional laparoscopy group (p=0.60). No difference in the rate of prior surgery was found between the groups (65% vs 52%, p=0. 35). No difference in the rate of prior surgery for endometriosis was found between the groups (43% vs 28%, p=0.26).

The mean ASRM score was 98 ± 49 in the robotic group and 86 (±49) in the conventional laparoscopy group, respectively (p=0.39). The mean Enzian score was 0.9 in the robotic group and 0.8 in the conventional laparoscopy group for the A classification, 2.1 and 1.9 for the B classification, and 1.5 and 1.4 respectively for the C classification.

Surgical findings and intra-operative complications.

Characteristics of the surgical procedures are presented in the Table 2. There was no difference between the groups regarding the type of rectal procedure. In the robotic group, 8 patients (35%) underwent a shaving, 6 patients (26%) a discoid excision, and 8 patients (35%) a segmental resection. In the conventional laparoscopy group, 10 patients (40%) underwent a shaving, 4 (16%) a discoid resection and 11 patients (44%) a segmental resection. In the robotic group 6 (26%) underwent a hysterectomy and 11 (44%) in the conventional laparoscopy group. A trend for a higher incidence of associated procedures was noted in the robotic group (p=0.06) (i.e. 2 (9%) partial bladder resection, 1 (4%) ureteral resection and 2 ileo caecal resection (9%)).

Anastomotic leakage diagnosed by leak test was observed in two patients (9%) in the robotic group requiring an immediate second rectal resection and anastomosis (none in the conventional laparoscopy group). Intraoperative complications occurred in two cases in the robotic group consisting in one vaginal opening and one incomplete resection by discoid excision requiring a segmental resection and one bladder injury in the conventional laparoscopy group (p=0.5).

An ileostomy was performed in three cases (13%) in the robotic group for colpectomy in two cases and rectal and ileocecal resection in one case. Ileostomy was required in six cases (24%) in the conventional laparoscopy group for low rectal anastomosis in two cases, colpectomy in two cases, excision of the Douglas pouch peritoneum and double resection in one case each. No difference in ileostomy was noted between the groups.

The mean total surgical room occupancy time were 281 ± 97 min in the robotic group and 208 ± 85 min in the conventional laparoscopy group (p=0.008). For the robotic group, mean docking time was 18 min. The mean total operating time were 221 ± 94 min in the robotic group and 163 ± 83 min in the laparoscopic group (p=0.03). The mean intra operative blood loss was 130 ± 86 ml and 108 ± 99 ml in the robotic and in the conventional laparoscopy group, respectively (p=0.43). None of the patients required transfusion during or after the surgery. No conversion to laparotomy was needed. In the robotic group, no conversion to conventional laparoscopy was needed.

Postoperative complications conventional laparoscopy group (p=0.18). Postoperative complications occurred in 6 cases in the robotic group, with three major complications requiring a radiological or surgical treatment (grade III complication according to Clavien-Dindo classification): one rectovaginal fistulae treated by ileostomy with spontaneous healing, one deep pelvic abscess and one parietal evisceration. No major complications occurred in the conventional laparoscopy group. Immediate postoperative voiding dysfunction was noticed in one case in the robotic group and four cases in the conventional laparoscopy group (p=0.22). Voiding dysfunction requiring a bladder self-catheterization more than 1 month after surgery was noticed in one case in each group. The proximal and distal margins of the resection were confirmed to be in sano in 14/15 patients (93%) in the robotic group and in 12/15 (80%) in the conventional laparoscopy group (p=0.27).

DISCUSSION

The results of the current pilot study support that robotic surgery is a reliable alternative to conventional laparoscopy for the surgical treatment of colorectal endometriosis.

Although no difference in intra and postoperative complications were noted between the groups, operating time was higher in the robotic group.

To our knowledges, no data comparing robotic to conventional laparoscopy for the surgical treatment of deep endometriosis with colorectal involvement are available. In the present pilot study, most patients underwent a conservative surgery consisting in a rectal shaving or discoid resection (58%) while a radical surgery consisting in a segmental resection was required in 42% of cases without difference between the groups. Although the current study is not randomized, it is important to note that no selection for robotic or conventional laparoscopy was done on preoperative characteristics as the route was based on the assess to the robotic room. Indeed, for the department of gynecology, robotic room was reserved once a week and twice a week every other week for the patients who were previously scheduled for colorectal surgery at one year. Finally, none of the patients refused a robotic approach.

Only few previous studies with small sample sizes, long periods of inclusion and high heterogeneity in endometriosis are available 3 22 23 24 25 . In a cohort of patients with severe endometriosis, Nezhat et al. observed longer operating time for robotic compared to conventional laparoscopy (251 min vs 173 min; p=0.0005) but without difference in intra and postoperative complications and in hospital stay [START_REF] Nezhat | Robotic-assisted laparoscopic treatment of bowel, bladder, and ureteral endometriosis[END_REF] . In our study, patients in the robotic and in the conventional laparoscopy groups had similar epidemiological characteristics (age, BMI, prior surgery for endometriosis) and similar extent in endometriosis as proved by the values of ASRM and ENZIAN scores. However, a trend for a higher rate of associated surgical procedures was noted in the robotic group (p=0.06) including ileocecal resection, partial bladder resection or ureteral resection.

As previous studies, we observed a higher operative time in the robotic group (281 min versus 208 min; p=0.008). Even when excluding the docking time (18 minutes on average), the robotic route was longer with a mean difference in operating time of 40 minutes.

Our results are in agreement with those of a Cochrane review showing that robotic gynecologic procedures (hysterectomy and sacrocolpopexy) were 40 minutes longer than conventional laparoscopy but including the docking time 12 27 . Therefore, a better criterion is probably the total surgical room occupancy time that was also higher for the robotic group (281 min vs 163 min, p=0.03). However, in the current study, the difference in both operating and surgical room occupancy time could be also explained by different parameters. First, a trend for a higher rate of associated surgery in the robotic group. Second, the initial experience of the two operators in robotic surgery. Indeed, using the CUSUM methods on operating time, a previous study on robotic rectal resection for cancer showed that the phase 3, representing the mastery phase, was achieved after 25 cases [START_REF] Bokhari | Learning curve for robotic-assisted laparoscopic colorectal surgery[END_REF] .

Except operating time, the crucial criterion to compare robotic and conventional laparoscopy is the incidence of complications. Using the Clavien-Dindo classification, the intra and postoperative complication rates were similar between the groups. However, a higher rate of grade III complication was found in the robotic group although not reaching significance (13% versus 0%). As for operating time, this could be explained by both the rate of associated procedures and the limited experience of surgeons in robotic with subsequent trend for a slight increase in hospital stay (8.0 versus 6.5 days) and in rehospitalization (9% versus 0%). Moreover, our complications rate is in agreement with those of a recent metaanalysis on laparoscopic colorectal resection for endometriosis involving 38 series with 3079 patients [START_REF] Balla | Outcomes after rectosigmoid resection for endometriosis: a systematic literature review[END_REF] . Finally, our rate of voiding dysfunction, that is one of the most frequent less than 8 procedures per year [START_REF] Bendifallah | Impact of hospital and surgeon case volume on morbidity in colorectal endometriosis management: a plea to define criteria for expert centers[END_REF] . Third, despite the small sample size, the advantage of the current study is offering data for power calculation for further trials. Finally, due to the short follow-up, it was not possible to evaluate according to the groups changes in symptoms, quality of life, sexual function and fertility outcomes.

Despite the limits of the present pilot study, our results support that robotic surgery is an adequate alternative to conventional laparoscopy for endometriosis colorectal resection.

Further studies are required to explore the non-inferiority of robotic surgery regarding postoperative complications. Moreover, potential benefit for the patient should be investigated.

Table 1 :

 1 Epidemiologic and imaging characteristics of the study population

	C	Robotic group (n=23)	Conventional	p-value
			Laparoscopy group
			(n=25)
	Age, years mean (± SD)	36 ± 7	37 ± 8	0.60
	BMI,kg/m2 mean (± SD)	25 ± 3	25 ± 4	0.91
	Prior abdominal surgery, n	15 (65%)	13 (52%)	0.35
	(%)
	Prior surgery for	10 (43%)	7 (28%)	0.26
	endometriosis, n (%)
	Pregnancy before surgery, n	9 (39%)	11 (44%)	0.73
	(%)
	Live birth before surgery, n	6 (26%)	9 (36%)	0.46
	(%)
	Infertility, n (%)	9 (39%)	9 (36%)	0.82
	-MRI	23 (100%)	25 (100%)	1
	-Rectal endoscopic sonography	13 (57%)	9 (38%)	0.19
	-Entero MRI	10 (43%)	8 (32%)	0.41
	-Cystoscopy	3 (13%)	1 (4%)	0.26
	MRI ENZIAN classification
	A, mean	0.9	0.8	0.92
	B, mean	2.1	1.9	0.51
	C, mean	1.5	1.4	0.75
	Indication for surgery, n (%)			0.77
	-Pain	14 (61%)	15 (60%)
	-Infertility	2 (9%)	1 (4%)
	-Pain and infertility	7 (30%)	9 (36%)

Table 2 :

 2 Surgical characteristics according to robotic and conventional laparoscopy groups

Table 3 :

 3 Intra operative and postoperative complications and voiding dysfunction according to robotic and conventional laparoscopy groups.

postoperative complication not taken into account by the Clavien-Dindo classification, was particularly low in the robotic group (4%) compared to previous studies affecting up to 20% of the patients underlying the feasibility of robotic nerve sparing surgery 16 30 31 .

Many advantages of the robotic techniques were already underlined: greater view with the three-dimensional visual system, motion range allowed by the articulated instruments, filtration of any natural tremor of the surgeon 32 33 . Then, we won't attribute the higher proportion of associated procedure in the robotic group to the better 3D visualisation.

Moreover, robotic procedure confers ergonomic advantages and the ability to sit. Robotic procedures appear to be associated with less fatigue for surgeons. However, advantages on intra-and postoperative complications, quality of life, patient's satisfaction on incisions and medico-economic have to be evaluated. In our population, all the associated procedures were planned before the surgery. Some limits of the current pilot study deserve to be underlined. First, our data corresponded to the initial experience in robotic of two experienced surgeons in laparoscopic colorectal resection for endometriosis that might be a source of bias especially concerning operating time and complication rate. Second, the number of patients included in the two groups was relatively low but on a short period reflecting the recruitment of an expert centre operating on severe forms as proved by the high rate of associated procedures to colorectal endometriosis. Graham et al reported their experience on robotic colorectal resection for endometriosis on 15 patients operated on a period of three year with an incidence of severe complications in one-third of the population [START_REF] Graham | A review of deep infiltrative colorectal endometriosis treated robotically at a single institution[END_REF] . Similarly, on a series of 10 cases of robotic colorectal resection for endometriosis on a period of two years, Morelli et al reported similar complication rate [START_REF] Morelli | Robot-assisted surgery for the radical treatment of deep infiltrating endometriosis with colorectal involvement: short-and mid-term surgical and functional outcomes[END_REF] . However, a recent study by Bendifallah and al underlined that the risk of complications after colorectal resection for endometriosis by conventional laparoscopy was