Joana Guerrin
email: joana.guerrin@gmail.com

A floodplain restoration project on the River Rhône (France). Analyzing challenges to its implementation Regional Environmental Change, 2014

Keywords: Floodplain restoration, Rhône, Floods, Failure

Floodplain restoration projects are part of sustainable flood management model. However, in practice, they are rarely implemented. We analyze the failure of a floodplain restoration project that was supposed to be implemented on the River Rhône (France). Based on the analysis of floodplain restoration projects implementation literature, we identified several constraints on the implementation of the project. In accordance with the literature, institutional factors were found to have played a critical role in the failure of the project.

Other factors such as opposing representations between inhabitants and river managers were also important. Moreover, the strong involvement of the State alongside river managers proved to be a major constraint on implementation.

Introduction

In accordance with current concerns about climate change, European States are reorganizing their flood management policies to incorporate practices that are consistent with sustainable development [START_REF] Guerrin | Le développement durable comme légitimation de l'action publique. Le cas des inondations du Rhône[END_REF]).

At regional and international levels, institutions such as the European Commission [START_REF] Solutions | Analyse Coût/Bénéfice Schéma d'optimisation des zones d'expansion des crues du Rhône, en aval de Viviers[END_REF]), the OECD (2010), the United Nations or the [START_REF] Wwf | Living with floods: achieving ecologically sustainable flood management in Europe[END_REF] promote the concept of sustainable flood management [START_REF] Guerrin | Remparts ou menaces? Trajectoires politiques de l'endiguement en France, aux Pays-Bas et aux Etats-Unis[END_REF]. In several countries including France [START_REF] Solutions | Analyse Coût/Bénéfice Schéma d'optimisation des zones d'expansion des crues du Rhône, en aval de Viviers[END_REF], the UK [START_REF] Werritty | Sustainable flood management: oxymoron or new paradigm?[END_REF][START_REF] Gardiner | The River Thames Strategic Flood Defence Initiative. A new approach to flood control measures[END_REF], and the Netherlands [START_REF] Roth | Rural solutions for Threats to Urban Areas: The Contest over Calamity Polders[END_REF][START_REF] Warner | La mise en oeuvre de "plus d'espace pour le fleuve" : les discours positifs et négatifs à Kampen, aux Pays-Bas[END_REF]Warner et al. 2013;[START_REF] Wiering | When water management meets spatial planning:a policy-arrangements perspective[END_REF], current norms on flood management policies focus on the importance of managing floods rather than defending against them. Public policies focusing on promoting environmentally sound and integrated measures for managing floods combine the possibility of human activity and risk occurrence (Moss and Monstadt 2008). They promote measures that enable populations to live with floods instead of tackling flood risk by heightening dikes. Floodplain restoration projects form part of this approach [START_REF] Ververk | Space for the River: a condensed state of the art[END_REF].

When accompanied by the construction of dikes, the development of floodplains for agricultural or housing purposes had hydrological effects (Pigeon 2012; [START_REF] Maltby | Managing riverine environments in the context of new water policy in Europe[END_REF]. Water storage areas used in the case of floods became reduced, accelerating water runoff, and increasing the risk of dike failure (Moss and Monstadt 2008). Floodplain restoration projects have been designed across Europe, especially since the 1990s, with the aim of tackling this issue. Floodplain restoration projects in general refer to "the creation of ecosystems typical of floodplains on low-lying land which exhibit a hydrological link between river and land" (Moss and Monstadt 2008). In practice, floodplain restoration projects consist of facilitating the return of water (in the case of floods) to an area that was flood prone in the past. However, two kinds of floodplain restoration project can be distinguished: i) projects whose primary aim is to recreate or enhance the ecological functions of the floodplain.

These kinds of project are labeled 'environmental restoration' or 'ecological restoration'; and ii) projects whose primary aim is to store water by causing the flood to flow to a protected plain, e.g. by reducing existing flood protection infrastructures, such as the dikes located upstream, to allow the expansion and storage of water in the case of flooding. These kinds of project used to be labeled 'calamity polders' and 'emergency storage areas' in the Netherlands [START_REF] Roth | Dealing with flood risk in an urban setting: Calamity polders and the politics of knowledge[END_REF] or 'washlands' in the UK [START_REF] Morris | A Framework for Integrating Flood Defence and Biodiversity in Washland in England[END_REF]. In our case study, we focus on the challenges involved in a project that consisted of restoring a floodplain for hydraulic purposes, called in French 'restauration de zone d'expansion de crues' (or ZEC).

The principle behind restoring a floodplain for hydraulic purposes is the idea of transferring flood flows from areas considered to be "highly vulnerable" (such as urban areas) to areas that are considered to be "less vulnerable" (as they are natural land and farmland) [START_REF] Solutions | Analyse Coût/Bénéfice Schéma d'optimisation des zones d'expansion des crues du Rhône, en aval de Viviers[END_REF]). Indeed, this transfer of risk may enable highly vulnerable areas to benefit from protection when natural or agricultural land is used for water storage (usually located upstream from a vulnerable area in order to reduce the water flow). In France, the State is currently reviewing existing flood risk policies on the River Rhône. This is being achieved through a series of projects including one that aimed to lower existing dikes to guarantee more protection for towns located downstream. However, even if floodplain restoration measures are promoted in flood risk literature, in practice they are rarely implemented (Moss and Monstadt 2008).

In this paper, we intend to contribute to understand this low implementation. We examine the challenges to the implementation of a particular floodplain restoration project on the River Rhône. After seven years of negotiations and conflicts between state engineers and riverbank inhabitants, the implementation of the project was abandoned. The aim of this paper is to understand the reasons for this failure. Beyond denouncing the low social acceptance of a challenging environmental policy, we seek deeper causes of failure, which are structural as well as situational, and therefore comparable with failures of other projects in Europe.

This article builds on an in-depth study of flood strategy on the River Rhône that has been implemented since major floods occurred in 2002 and 2003. We analyzed the creation of an institution ("Plan Rhône") that provided a new model for flood risk governance at the level of the river. In particular, we focused our analysis on a project designed by the Plan Rhône partners to restore a floodplain in the Lower Rhône river basin. We analyzed both the local and national controversies surrounding this project involving inhabitants, elected representatives, the public administration and scientists. In this research context, we collected empirical data from several sources. We conducted 62 semi-structured interviews between 2010 and 2012 with different kinds of actor: Plan Rhône participants, central and local State officials and elected representatives, opponents of the floodplain restoration project (inhabitants, associations, local authorities). We reviewed the gray literature produced by Plan Rhône (experts' reports, information provided to the public) and other institutions on floods in general and on the River Rhône in particular. We consulted the scientific literature and experts' reports on floods. We analyzed letters exchanged between Plan Rhône and public officials and local governments about the floodplain restoration project. We consulted archives on the history of the Lower Rhône and the construction of its infrastructure as well as French historical literature on flood management of the River Rhône. We then conducted a qualitative analysis of this empirical material to propose an interpretation of the failure of the floodplain restoration project.

The paper is organized as follows: In the first section, we review the literature on floodplain restoration policy and the potential driving forces behind, and constraints on, implementation. In section two, we present the case study. In section three we analyze the challenges faced by engineers who supported the floodplain restoration project by comparing the literature and the case study.

Identifying the driving forces behind, and constraints on implementation of floodplain restoration projects

In this section we present the scientific literature dealing with the implementation of floodplain restoration projects. We analyzed this literature in order to identify the main driving forces behind the implementation of such projects, and their constraints.

In selecting the literature, we considered floodplain restoration in its broad sense. However, we limited our selection to scientific articles and book chapters dealing with the implementation of floodplain projects in Europe and written in French or in English. We chose articles that tackled social and political aspects of project implementation (i.e. we did not focus on technical aspects). We selected documents using the snowballing method starting with core articles and using the list of references to identify others. We stopped our search when the information we were finding in the articles appeared to be covered by those we had already read. We finally selected 14 articles. The small number of articles is due to our strict selection criteria.

The literature analysis revealed five categories of driving forces behind, and constraints on the implementation of floodplain restoration projects: institutions, participation, science and policy, socio-physical features, and economics. The results of this analysis are summarized in table 1.

Floodplain restoration, from Europe to the Rhône

The River Rhône has been considerably modified throughout history. After major floods in 1856 the Emperor Napoleon III constructed large dikes along the delta [START_REF] Picon | Gestion du risque inondation et changement social dans le delta du Rhône[END_REF]). More recently, after World War II, the government undertook an extensive river taming project with the aim of promoting river transport and generating hydraulic power [START_REF] Pritchard | Reconstructing the Rhône: The Cultural Politics of Nature and Nation in Contemporary France, 1945-1997[END_REF]). The public National Rhône Company CNR (Compagnie Nationale du Rhône), partly privatized in 2001, was dedicated to the development of the River Rhône. It received specific missions of public interest: developing navigation, hydroelectric power and irrigation systems in the Rhône river basin (Giandou 1999). The CNR undertook major works on the river and constructed several dams and levees [START_REF] Pritchard | Confluence. The Nature of Technology and the Remaking of the Rhône[END_REF]. Later nuclear power plants were built on the banks of the newly channeled river. These works deeply changed the river landscape, and influenced its hydraulic regime [START_REF] Pritchard | Confluence. The Nature of Technology and the Remaking of the Rhône[END_REF]), but the inhabitants only noticed many years after the works were completed.

Between the 1950s and the 1990s, no major flood event occurred on the Rhône [START_REF] Picon | Gestion du risque inondation et changement social dans le delta du Rhône[END_REF]). Based on these forty years, one could have concluded that the CNR works had a beneficial impact in terms of flood protection. However, following the first major flood event in 1993, floods found their way back onto the political agenda. In fact, CNR infrastructures, including levees, were not intended to protect riverbank inhabitants from floods but to channel the river for hydropower and navigation purposes. Where hydropower plants were built, houses located behind the levees were protected de facto against 1000-year flood events. But other houses, located in areas that were not concerned by hydroelectric power, were subject to intense flooding events.

Since the 1990s, several dramatic floods have occurred on the Rhône: in 1993Rhône: in , 1994Rhône: in , 2002Rhône: in , and 2003. Hundreds of houses were impacted by the Rhône and its tributaries and sometimes even lives were lost. This troubled period obliged the State to take measures. In 2003, a major study on the Rhône floods was released in an attempt to understand the river basin system and make proposals for policies (Territoire Rhône 2003). In 2004, the Prime Minister asked the Prefect (the State's representative in the Rhône-Alpes Region whose responsibility covers the whole Rhone river basin) to design a new flood management strategy for the River Rhône. In collaboration with the Prefect, State representatives, and the elected presidents of the administrative Regions, a contract called "Plan Rhône" was drawn up. This contract, which concerns the period 2007 to 2013, financially linked the French State, the European Union, the CNR and the main towns concerned as well as the Regions bordering the Rhône in order to address flood issues at the level of the river basin. This contract entailed a multilevel and multi-sector policy on the scale of the River Rhône. Indeed, Plan Rhône combined policies concerned with flood management but also with tourism, culture, energy, water quality and transport.

One of the main aims of Plan Rhône was to produce a new strategy for flood management. Part of this plan, namely the flood theme, was piloted by a team called "Mission Rhône" comprised of State engineers. Mission Rhône is part of the Ministry of the Environment's decentralized regional services (called the Regional Direction of the Environment, Planning and Housing or DREAL). Between 2005 and 2013, Mission Rhône engineers proposed and started to implement a flood management strategy. To that end, Mission Rhône separated the river into three geographical entities: Upper Rhône, Middle Rhône and Lower Rhône (Figure 1). For each sector, public consultations took place and a local strategy was created. Here we focus on the strategy designed for the Lower Rhône, that included floodplain restoration projects. The strategy proposed by Mission Rhône for the Lower Rhône followed a particular rationale. It aimed to address the risk of dike failure (which had happened in the Rhône delta in 1993, 1994 and 2003) by modifying the distribution of risk they considered unequal. Some plains were frequently flooded whereas others were protected behind CNR dikes. What is more, several towns of high economic and demographic importance located downstream were deemed overly vulnerable, and under too much water pressure in the event of flooding.

The strategy consisted of several actions aimed at "controlling the overflow"(DREAL Rhône Alpes 2009; Territoire Rhône 2003) in the case of flooding through a Floodplains Optimization program. This program was planning on one hand, to improve flood protection of certain rural floodplains subject to frequent flooding (on average once every ten years, highlighted in blue in Figure 1), and on the other hand, to increase the water storage capacity in two floodplains by lowering existing flood-defense infrastructure (highlighted in red in Figure 1). The larger is a 1,300 ha plain located behind a major CNR dike and therefore protected against Rhône floods up to 1,000 year return period. Land use is agricultural plus residential areas (40 farms and homesteads as well as residential houses) (BRL Ingénierie 2008). This project also provided for the reinforcement of dikes around the Rhone river delta and around major towns. This program was justified by the need to improve solidarity among the sections of the river, between upstream and downstream inhabitants, as well as between the two banks (DREAL Rhône Alpes 2009).

The floodplain restoration project met with the disapproval of local representatives. In 2012, after seven years of public consultation, negotiation, and production of experts' reports, the floodplain restoration project was abandoned. Was this failure due to local resistance or to other constraints? In the next section we compare the driving forces cited in the literature and failures of project implementation with our case study.

Constraints on the implementation of the floodplain restoration project on the Rhône

Institutions

The floodplain restoration project was led by a young institution (Plan Rhône) that lacked power and legitimacy.

Plan Rhône was created in 2007 to design a new flood management strategy. It brought together actors who previously had conflicting relationships and opposing interests, in particular the Regions, the State, and the CNR [START_REF] Bethemont | Le Rhône entre nation et région Revue de géographie de Lyon[END_REF]. The team supporting the project, Mission Rhône, had no power to decide whether to raise or to lower a dike (since this is subject to State regulation and concerned the CNR). Therefore it was obliged to negotiate with the CNR and local authorities. The CNR and Mission Rhône had conflicting priorities: electricity production versus flood management. Mission Rhône had limited power to negotiate with the local inhabitants since neither urban planning nor property rights issues fell within its authority. Moreover, it was not responsible for project implementation nor could it pay financial compensation to the local stakeholders. Mission Rhône could only encourage local authorities to implement the project and negotiate compensation between territories at the local level. This absence of leadership was combined with little support from local stakeholders, local authorities, the central State and the CNR. In particular, the representatives of the two local municipalities of the floodplain supposed to be restored were concerned with the project's impact on economic development of the area. The two mayors raised concerns about the impact of floods on farms and houses. They firmly opposed the project's implementation. Although they belonged to opposing political parties (right-wing and left-wing), they joined forces to oppose the project. This union was illustrated by newspaper articles entitled "The Rhône battle" or "A mayoral coalition against Plan Rhône", picturing the two mayors standing side by side next to the river (Dauphiné Libéré, June 12, 2008). In addition, together they hired the services of a hydrologist and an urbanplanner to produce a counter evaluation.

As well as meeting opposition from the local municipalities, the project also raised concerns among inhabitants and elected representatives of other floodplains. Associations, inhabitants and representatives expressed their fears concerning the consequences of future Rhône floods at public meetings. The Lower Rhône flood management strategy revealed that the flood-prone character of rural floodplains was beneficial for urban areas.

As a result, inhabitants raised concerns about insurance cover, arguing that flooding triggered by human activities might not be covered by insurance policies, since it was not comparable to a natural flood. Inhabitants of several floodplains along the Lower Rhone felt concerned by the situation of the floodplain intended for restoration. They grouped together, along with flood victim associations, to claim for the recognition of a special status for inhabitants living in areas allowing for flood expansion. This claim was later endorsed by elected representatives at the regional and departmental levels. In 2005 and in 2010 a group of deputies presented two legislative proposals before the French National Assembly to grant particular benefits to inhabitants in "flood expansion" areas, in particular through tax exemption (Law proposal N° 2739(Law proposal N° (2005) ) and Law proposal N° 2596 (2010): « visant à accorder un statut particulier aux communes et aux administrés situés dans les champs d'expansion de crues »).

However, these claims were refused by the Ministry of the Environment. A letter from the Ministry to a Deputy (April 24, 2007) stated that the Rhône River floodplains called "ZECs" were "naturally" flood prone, and as such, were not eligible for compensation since the dikes did not worsen their flood character in comparison to a natural situation. In 2010, a meeting was organized between elected representatives from the Lower Rhône and the Office director of the Ministry of the Environment in which the latter declared that granting a particular status to all the ZECs would be excessive since, in general, floodplains were naturally flood prone (from the minutes of this meeting, June 17, 2010). Granting a particular status to the inhabitants of restored floodplains could have facilitated local acceptance of the floodplain restoration project, as a local newspaper pointed out: "Rhône. Flooding, okay, but only with a particular status" (Midi Libre, June 19, 2010).

In addition, only limited support for the project came from the water institution, the CNR. Restoring the floodplain meant modifying a CNR dike by lowering it. Since the flood events in the 1990s, the CNR had been constantly accused by flood victims' associations and inhabitants of being responsible for the floods. Even though such responsibility has never been acknowledged by experts [START_REF] Picon | Gestion du risque inondation et changement social dans le delta du Rhône[END_REF], the CNR position regarding flood management was not proactive, but rather defensive. Since flood management is not part of its mandate, the company was not particularly willing to modify its dikes not only for financial reasons but also because of the political stakes involved.

In addition, little support came from the central government. As part of the Ministry of the Environment regional office, Mission Rhone depends on decisions made by the central government. In 2009, the Ministry expressed doubts about the feasibility of the project, in particular from the result of an expert evaluation made by Central State engineers criticizing the feasibility of the floodplain restoration project (Creuchet et al. 2009). Mission Rhône conducted many feasibility studies for the floodplain restoration project but had no power of decision regarding its implementation. Even if Mission Rhône was in favor of its implementation, as civil servants and State administrators, they did not have the right to implement the project as commissioners. Local authorities (an association of towns, or Departments) could have been commissioners but they did not wish to take responsibility for the project. Just before the decision to abandon the project was made public (in 2012), the last chance the project had of being implemented depended on the drawing up of a new law enabling the State either to take responsibility for the project or to oblige actors such as the CNR to take over project implementation. The Ministry did not choose this regulatory path and the project was officially abandoned in 2012 (a letter from the Prefect, dated 17th April 2012, announced the decision by the Plan Rhône partners to abandon the floodplain restoration project).

Plan Rhône was defined at the level of the river but was led by the State. In the discourses of local representatives as well as inhabitants, the State did not have the legitimacy to organize implementation of a floodplain restoration project. Moreover Plan Rhône and Mission Rhône were young institutions with no proven record of expertise. However the case of the Rhône is particular in the sense that a major part of the river is managed by the CNR, as the company is in charge of hydropower production but also deals with channels and dikes. The CNR had an interest in following a path of dependency. No formal association at the level of the river links local authorities or municipalities together (Pigeon 2012). This kind of association could have enabled a real decentralized flood policy at the level of the river and overcome local opposition. Such an institution existed on the River Rhone but was never recognized officially by the State. The State did not leave room for truly decentralized flood management.

Participation

On the Rhône, the participation of local representatives and inhabitants was organized through consultation committees. However, the extent of participation was limited. This participatory approach was introduced quite early in the process, but the idea of restoring a floodplain came from an expert evaluation that was commissioned by the State before the participation committees started (Territoire Rhône 2003). Sites had already been selected when local representatives learned about the project. The committees were organized by the institution in charge of the project implementation: Mission Rhône itself. In the participation committees, experts and representatives who supported the project presented their ideas to the public who generally raised concerns. Experts gave usually technical answers aimed at convincing the public of the project's advantages. But views and values regarding the project were also conflicting. Inhabitants and local representatives denounced power and territorial inequities (urban and downstream interests over rural upstream interests), and the responsibility of the State and the CNR year flood) on the whole river and its tributaries (DREAL Rhône Alpes et CNR 2010). This 3.75 meter water level was considered to be socially and politically unacceptable by the central State engineers. To reduce the impact of the flood, the following scenario reduced water storage capacity to 32 million cubic meters (under 2.2 meters of water). For this kind of flood, the decrease in the water level downstream would be 10 to 15 centimeters, whereas with the previous scenario it was 20 to 25 cm (DREAL Rhône Alpes et CNR 2010).

Although the hydraulic benefits were limited, interviews with the Mission Rhône engineers revealed that the floodplain restoration project was advantageous for other reasons. Indeed, the flood management activities of Plan Rhône were partially funded by the European Union through the European Regional Development Funds (ERDF), which could be used for flood prevention but only under certain conditions: to implement measures consistent with the approach of the European Directive, i.e. environment-friendly measures and not dike heightening. Moreover, an existing water planning document on the Rhône prevented the construction of dikes when no hydraulic compensation was planned to store the extra water (SDAGE 2010(SDAGE -2015)). As such, the floodplain restoration project was a necessary condition to allow the heightening of dikes on the River Rhône.

Socio-physical features

Another problem with project implementation was defining a natural flood. Restoring the flood-prone character of a plain implies referring to a time when the plain used to be flood prone. In the Lower Rhône flood management strategy, the reference used for floodplains to be restored is the 'ZEC". Plan Rhône participated in the publication of a book in which the ZEC concept is defined thus: "A ZEC (…) is a floodplain subjected to natural floods. This expression is used to designate 'areas with little or no urbanization and development, where a flood can store a large amount of water, such as natural areas, farmlands, urban and peripheral green areas, sports fields, car parks" (Bravard, J.-P. and A. Clémens, Eds. (2008). Le Rhône en 100 Questions Behind this acronym are entangled ideas about the naturalness of a risk as well as the utility of a flood, expressed by the idea that a ZEC is supposed to be undeveloped and is useful to store water in the case of flood.

. Lyon, GRAIE).

Several rural areas were identified as ZECs on the Lower Rhône by the hydrological study (Territoire Rhône 2003). This study reported that the CNR constructed 150 km of dikes on the Rhône banks (or 35% of its course), transforming 120 km² of floodplains into flood protected areas, which represented 18% of the land that was impacted by the 1856 flood. The study underlined the artificial nature of flooding due to the CNR hydraulic infrastructure, and distinguished between the current flood-prone areas, called "natural flood expansion fields" and the former floodplains now protected by CNR dikes. However, under the Lower Rhône river flood management strategy, even the former floodplains were labeled ZECs.

Designating former floodplains as ZECs actually refers to natural flooding. However, the Rhône hydrological regime was modified by CNR works. The term ZEC today designates plains that are considered to be flood prone based on the modeling of a past event in a currently urbanized context. This fuzzy definition of a ZEC led to discontent among the inhabitants of those areas. Some inhabitants realized that their area's flood-prone character was useful to downstream towns, and consequently claimed compensation or at least the recognition of a particular status. Others (who lived in the floodplain that was supposed to be restored) discovered that after fifty years of being protected they might again become flood prone. Given the urban development that has occurred in the last fifty years in rural areas, as well as changes in agricultural practices, restoring flooding in the territory led to a considerable degree of local discontent.

Economics

The floodplain restoration project was not a "low-cost project". The cost of the works to allow the restoration of the floodplain was estimated at 10.4 million Euros, not including the cost of the downstream floodplains whose protection was supposed to be enhanced. In total, the cost of the project was estimated at 54 million Euros (Egeo Solutions and Ledoux 2011).

Locally, no economic incentive was available to local stakeholders. No direct financial compensation was proposed to the inhabitants of the plain for the water storage its restoration would allow. This was because of the idea that the Rhône floodplain is naturally flood prone. Indeed, the law does not permit the payment of compensation to inhabitants for reducing flood protection but only for an increase in flood risk. Since Rhône floodplains were considered naturally flood prone, the floodplain restoration project was still improving the situation in comparison with a no-dike situation. As such, State officials were not allowed to pay compensation. Such financial incentives could have been funded by downstream plains that were supposed to benefit from the project. However, the downstream plains did not consider the potential benefit high enough to take responsibility for implementing the project and organizing compensation locally. This is also explained by the scientific uncertainties surrounding the project findings that were expressed in public meetings. Mission Rhône had no power to suggest purchasing the land belonging to farmers and inhabitants or to pay them direct financial compensation. Farmers were consequently not economically motivated to accept a project that as far as they were concerned, above all represented constraints. Mission Rhône was proposing to let the flood enter a plain where land was particularly good for growing crops, where houses were built and where life had developed behind large dykes for 40 years, with no financial compensation in return. Farmers -more than anyone elserecall the times when the plain used to be flood prone. They believe that farming techniques and life style have changed too much for agriculture to be adapted to flooding.

Conclusion

Restoring a floodplain of a modified and channeled river such as the Rhône proved to be a challenge. The project we analyzed came up against a number of difficulties and was finally abandoned. To understand the reasons for this failure, the indicators identified in the literature proved to be particularly accurate. However, some could be added to the list. The literature recognizes that above all institutional factors explain the failure or success of floodplain restoration projects. On the Rhône, the leading institution in charge of the project implementation was created at the river-basin level, supposed to be the right scale to tackle 'wicked problems' such as flood risk [START_REF] Varone | Functional regulatory spaces[END_REF]). However, this institution was not legitimate and sufficiently powerful support the project.

Moreover, it impeded local elected representatives from organizing and taking over the implementation process.

The lack of legislative flexibility impeded negotiation with the inhabitants who claimed their special status should be recognized. The artificial character of a flood provoked by a floodplain restoration project created insecurity among the inhabitants who feared losing insurance cover. Regarding participation, the project did not empower local actors sufficiently to reinforce the legitimacy of the leading institution and to enable local support. The fact that the participative committees were organized by the institution in charge of the project implementation was not adequate. As regards science and policy indicators, the project suffered from hydraulic uncertainty that provoked concerns among the local actors, largely because the interactions between state engineers and local actors were mainly technical. Other institutional reasons lay behind the reasons for restoring the floodplain, but hidden by hydraulic narratives that suffered from scientific uncertainty. The proponents of the floodplain restoration project committed to its implementation before carrying out detailed studies. We did not observe opposing representations regarding restoration between local actors and Mission Rhône engineers, but rather, opposing representations about the objectives to be pursued: the engineers gave greater importance to flood-risk sharing whereas local actors gave greater importance to keeping their flood security standards.

Another difference of standpoint concerned local actors' view of the correct reference to use when considering the flood-prone character of a plain: proponents of the project, along with the central administration, considered the time when the plain was not protected by dikes, whereas the local actors took as a reference the 'protected' situation. No social science study had been carried out at the design stage of the project to identify those differences of standpoint. Physical and sociological features identified in the literature did not play a large role in the project failure, except the fact that the floodplain intended for restoration had in the past benefited from a high flood defense strategy that proved, indeed, difficult to challenge. Regarding the economic indicators, what played a role in the failure of the project was the absence of compensation funds granted to the local actors. This is linked to what the law considers to be a natural flood, and is another illustration of opposing terms of reference between project proponents and local actors. Maybe those conflicting representations could have been identified, and tackled, through a sociological study.

Author-produced version of the article published in Regional Environmental Change, 2015, N°15(3), p.559-568 The original publication is available at http://link.springer.com Doi: 10.1007/s10113-014-0650-8

Figure 1 :

 1 Figure 1: Map of Plan Rhône territory. It represents the River Rhône, the administrative Regions surrounding the River (Plan Rhône partners), the sub-basin areas (Upper, Middle and Lower Rhône) as well as the area concerned with the floodplain restoration project.

Table 1 : Potential constraints on and driving forces behind implementation of floodplain restoration projects according to the literature Potential driving forces for implementation Potential constraints on implementation Institutional Strong

 1 , legitimate, large, well-funded lead organization, with clear remits and proven ability to work with other stakeholders and with charismatic individuals (Adams et al. 2005) Small or young lead organization with lack of secure core funding, no proven track record in project management or substantial planning capacity, weak leadership (Adams et al. 2005) Institutional structure appropriate for the multiple objectives of floodplain restoration (Hodge and McNally 2000), concerning not only water but also property right issues (Roth and Winnubst 2009) Small number of partners (Adams et al. 2005) Issues of coordination between sector-based public agencies and between administrative levels ; conflicting priorities between partners (Turner et al. 2000; Adams et al. 2005; Moss and Monstadt 2008; Adams and Perrow 1999); Support from and/or partnership with NGOs and local associations (Adams et al. 2005; Pedroli et al. 2002) Design not led by grassroots local needs (Adams et al. 2005) Local communities value the environment (Adams et al. 2005) Water institutions that participate in the implementation are friendly to environmental issues (Hodge and McNally 2000)Local communities value flood defense goals over environmental concerns(Adams et al. 2005; Moss and Monstadt 2008; van der Werff 2004). Restoration interests opposed to flood defense goals of planning organizations ; inertia of the traditional flood defense and river regulation regimes(Adams et al. 2005; Moss and Monstadt 2008) Policy and planning controls unable to limit urbanization of floodplains(Moss and Monstadt 2008)

Author-produced version of the article published in Regional Environmental Change, 2015, N°15(3), p.559-568 The original publication is available at http://link.springer.com Doi: 10.1007/s10113-014-0650-8

Author-produced version of the article published in Regional Environmental Change, 2015, N°15(3), p.559-568 The original publication is available at http://link.springer.com Doi: 10.1007/s10113-014-0650-8 regarding the last floods. But this kind of participation was not considered to be constructive or legitimate by Mission Rhône.

The organizers were not obliged to take public participation into account since the assembly had no decisionmaking power. Moreover since 'the public' represented a broad, heterogeneous audience, it was difficult to consider that it carried a clear message and unified interests. In practice, inputs from the public did not help build the project design.

What is more, the two mayors concerned by the floodplain restoration project proposed an alternative project, which consisted of creating several water storage tanks in many plains along the Lower Rhône, in order to distribute the burden of water storage among more municipalities. The idea was to turn the calamity polders, which were considered to be 'passive', into 'active' polders. However, according to Mission Rhône engineers, this project was not feasible since it would not deliver sufficient storage capacity.

A real communication strategy was developed by Mission Rhône. A full-time post in Mission Rhône is dedicated to communication. Before each public committee meeting, invitations and summaries of previous meetings were sent to the participants. Workshops and conferences were organized by Plan Rhône about several of their projects. However regarding the negotiations about the floodplain restoration project, nothing really constructive was achieved. Mission Rhône engineers did not have enough power to respond to the stakeholders' demands. In addition, they tried to educate the inhabitants and political representatives rather than to construct a shared view of the project. They did not incorporate public inputs in the project; they were not powerful enough to negotiate with the local representatives, and their decision-making process was not sufficiently transparent.

Science and Policy

In this project, few links were created between science and policy. Expert evaluation was produced by research consultancy and studies were commissioned and coordinated by Mission Rhône. The results were presented in consultative meetings but there was a knowledge gap between the experts and the public. No particular social science expert evaluation was commissioned in order to include social and political issues in the project design.

Mission Rhône did regularly consult a "scientific committee", however this was mainly limited to technical issues, and did not grant the committee decision support.

Scientific uncertainty was high regarding the water storage capacity of the floodplain as well as the potential water level in the plain in the case of floods. This uncertainty about the behavior of water flow, along with the uncertainty about the impact of the project on downstream water levels, contributed to the prevention of support among local stakeholders.

The reason used to justify the restoration of the floodplain was primarily hydrological. However, detailed hydrological studies concluded that this narrative was questionable. Indeed, the rationale of the Lower Rhône flood management strategy was constructed on a study that included the whole Rhône (Territoire Rhône 2003).

In this study, the principle of restoring a floodplain was considered to have potentially positive hydrological effects on downstream plains and towns. However, later, more detailed studies revealed that the water storage capacity was not as high as planned. A micro-scale study revealed that, due to the slope of the land and the existence of an urban neighborhood, the floodplain could store less water than originally envisaged (BRL Ingénierie 2008). Indeed, one of the first scenarios planned to achieve a water storage capacity of 67 million cubic meters (under 3.75 meters of water) in the case of an 'generalized exceptional flood' (greater than the 400-

Participation

Participation organized at an early stage of the implementation process (Eden and Tunstall 2006), active (Maltby 1991), including all stakeholders [START_REF] Morris | A Framework for Integrating Flood Defence and Biodiversity in Washland in England[END_REF], enabling open discussion of a range of views and values (Warner 2010).

Implementation models that develop a 'deficit model' of public understanding (i.e. technocratic environmental management, top-down approaches, expertise monopolized by the scientific community and policymakers) are more likely to fail (Eden and Tunstall 2006;Roth and Warner 2007;Adams et al. 2005;Roth and Winnubst 2009) Identification of local people's aspirations and priorities for a river site and incorporate them in the design of the project (Eden and Tunstall 2006) Consider alternatives to the project proposed by local actors (Warner 2010) Mismatch between the expectations of restoration and policy workers and those of their local publics (Eden and Tunstall 2006) Concerned population learns about the project plans when the sites have already been selected (Roth and Warner 2007) No link between participation and decision-making (Warner 2010) Negotiation skills of river managers (Adams et al. 2005;Roth and Warner 2007;Maltby 1991). Education programs, management training within water management institutions (Maltby 1991) Identify the needs and aspirations of local inhabitants and link the restoration project to their interests, in particular regarding flood risk concerns (Adams et al. 2005;Nedelcu et al. 2007;Eden and Tunstall 2006).

Science and Policy

Incorporating social science at the design stage of the project (Eden and Tunstall 2006;Brouwer and van Ek 2004;Turner et al. 2000) Failing to consider the sociopolitical issues at play can exacerbate conflicts (Eden and Tunstall 2006).

Making complex issues comprehensible to stakeholders (Adams et al. 2005) Shared vision of flood storage objectives (Moss and Monstadt 2008) Scientific uncertainties, e.g. behavior of flood waters (Adams and Perrow 1999;Turner et al. 2000). Opposing representations of restoration that can lead to misunderstandings and conflicting interests (Eden and Tunstall 2006;Adams and Perrow 1999;[START_REF] Morris | A Framework for Integrating Flood Defence and Biodiversity in Washland in England[END_REF].

Socio-physical features


Marisol Carrillo-Solano

Smaranda Leu-Semenescu

Jean-Louis Golmard

Elisabeth Groos

Isabelle Arnulf

Sleepiness in sleepwalking and sleep terrors: a higher sleep pressure?

Keywords: Parasomnia, Sleepwalking, Sleep terrors, Sleepiness, Sleep pressure

Introduction

Sleepwalking (SW) and sleep terrors (ST) are inappropriate, mostly amnestic, behaviors occurring upon a partial arousal from N3 sleep [START_REF]The international Classification of Sleep Disorders[END_REF]. These non-REM sleep parasomnias are common in children but may persist (and sometimes appear) in up to 2-4% adults [START_REF] Ohayon | Night terrors, sleepwalking, and confusional arousals in the general population: their frequency and relationship to other sleep and mental disorders[END_REF][START_REF] Ohayon | Prevalence and comorbidity of nocturnal wandering in the U.S. adult general population[END_REF]. Sleep terrors commonly overlap with sleepwalking in adults, either at the same moment (e.g., fear behavior and shouting, followed by a frenzied escape from the bed) or at different periods during the night. In addition to causing injuries to self and others, these nocturnal parasomnias impact upon daytime functioning, as recently shown by several clinical works [START_REF] Zadra | Somnambulism: clinical aspects and pathophysiological hypotheses[END_REF]. Adults with SW/ST often feel ashamed and anxious about their disorder, and they report lower quality of life, more difficulties in initiating and maintaining sleep, higher levels of anxiety, and daytime fatigue than healthy controls [START_REF] Lopez | Functional impairment in adult sleepwalkers: a case-control study[END_REF]. Excessive daytime sleepiness is in particular a recent matter of concern in sleepwalking. Indeed, a score greater than 10 on the Epworth sleepiness scale is reported by 47% of 43 patients with SW/ST in Paris, France [START_REF] Oudiette | Dreamlike mentations during sleepwalking and sleep terrors in adults[END_REF], 42% of 100 adult sleepwalkers in Montpellier, France [START_REF] Lopez | Functional impairment in adult sleepwalkers: a case-control study[END_REF], 41% of 71 patients with SW/ST in Paris, France [START_REF] Arnulf | A scale for assessing the severity of arousal disorders[END_REF], 46% of 70 adult sleepwalkers in Montreal, Canada [START_REF] Desautels | Daytime somnolence in adult sleepwalkers[END_REF], but only 15% of 32 young subjects with sleepwalking in Prague, Czech Republic [START_REF] Bušková | The course and character of sleepwalking in adulthood: a clinical and polysomnographic study[END_REF]. This increased feeling of sleepiness is substantiated by a mean daytime sleep onset latency shorter than 8 min on multiple sleep latencies in 7/10 sleepwalkers in a small series [START_REF] Montplaisir | Does sleepwalking impair daytime vigilance?[END_REF], whereas only the first morning nap of 4 naps occurred more rapidly in patients than in controls in a larger series [START_REF] Lopez | Objective daytime sleepiness in patients with somnambulism or sleep terrors[END_REF].

Why are nearly half of adult sleepwalkers feeling abnormally sleepy during the daytime? Is excessive sleepiness a consequence of fragmented sleep (especially fragmented N3), of nonrestorative sleep properties, or of the clinical severity of the disorder? Recently, some of these questions were examined in 70 patients with SW studied during a single night. No common sleep characteristics, including the intensity of slow wave activity (a marker of sleep restorative properties that may be altered in sleepwalking/sleep terrors) or the number of N3 awakenings, predicted the daytime level of sleepiness [START_REF] Desautels | Daytime somnolence in adult sleepwalkers[END_REF]. We aimed to replicate this study in a larger sample, taking advantage of retrospective analysis of routine patients charts in our unit, who underwent not one but two consecutive nights of polysomnography (a routine procedure which increases the chance of findings markers of SW/ST, and could allow to avoid first night effects and post-deprivation sleep rebound), and to examine, in addition, whether the characteristics and severity of SW/ST, measured using the Paris Arousal Disorder Severity Scale [START_REF] Arnulf | A scale for assessing the severity of arousal disorders[END_REF], would determine the level of daytime sleepiness in adults with SW/ST.

Methods

Patients

All consecutive patients with confirmed SW and ST seen in the adult sleep disorder unit of the Pitie-Salpetriere university hospital were included from January 2012 to June 2014. They had to meet the international criteria for SW and ST, including the following: [START_REF]The international Classification of Sleep Disorders[END_REF] a history of SW defined by complex behaviors that are usually initiated during arousals from slow-wave sleep and culminating in walking around with an altered state of consciousness and impaired judgment; or (2) a history of ST defined by autonomic nervous system responses of confusional arousal episodes, sitting up in bed, perhaps thrashing about or crying or screaming inconsolably, with a fast heart rate and rapid breathing, and all of these episodes were accompanied by misperceptions of the environment, impaired judgment, and frequent retrograde amnesia as assessed by the patient and bed partner or parents [START_REF]The international Classification of Sleep Disorders[END_REF]. Patients with parasomnia overlap disorders (wherein sleepwalking/sleep terrors are combined with REM sleep behavior disorders), nocturnal epilepsy, sleep sex or sleep-related eating disorders (as the exclusive symptoms) and patients with psychosis or concomitant severe psychiatric disorders (including current depression) were excluded. The clinical diagnosis of ST and SW was, in addition, supported by measures from videopolysomnography, performed to exclude other diagnoses and to document either confusional arousals, frequent (more than 3) awakenings from N3 or dissociated arousals (coexistence of markers of local sleep and local waking, either in the same or in different EEG channels), as a clinical routine in the sleep unit.

Because this study was a retrospective collection of clinical and polysomnographical measures from chart review, the local ethics committee (CPP Paris IDF 6) waived written consent from the patients, provided that they had given their oral consent for their data to be anonymously collected, which was the case here.

Clinical investigations

All patients were interviewed by a sleep physician (neurologist or psychiatrist), including the screening for any concomitant anxiety or mood disorder. They routinely completed the Epworth sleepiness scale (ESS) at time of the videopolysomnography [START_REF] Johns | A new method for measuring daytime sleepiness: the Epworth Sleepiness Scale[END_REF]. One hundred and eighteen patients (20 having spent one night and 98 having spent two consecutive nights) completed the Paris Arousal Disorders Severity Scale (PADSS) composed of three parts. The PADSS-A is an inventory of 17 abnormal amnestic behaviors scored as never (0), sometimes (1) and often (2) and yields a maximum score of 26; PADSS-B evaluates the frequency of behavioural episodes from 0 (never) to 34 (several times per night); PADSS-C evaluates the general consequences of the disorder, including injury to oneself (0 to 2) or others (0 to 2), disturbance of others' sleep (0 to 2), morning tiredness (0 to 2), and psychological (shame, anxiety) consequences (0 to 2), yielding a maximum of 10 [START_REF] Arnulf | A scale for assessing the severity of arousal disorders[END_REF]. The total of the scale is 50 and a score greater than 13 has a high sensitivity and specificity for separating patients with SW/ST from healthy controls and from patients with REM parasomnias.

Video and sleep monitoring

The videopolysomnography was performed over two consecutive nights in 124 patients and a single night in 34 additional patients (mostly because they could not stay for a second night or because we could not rapidly offer them a second night). It included 10 electroencephalography (EEG) leads (A1; A2; Fp1; C3; T3; O1; Fp2; C4; T4, O2) acquired in a monopolar referential montage and displayed on screen as bipolar, with sleep stages scored on the Fp1-C3, C3-A2 and C3-O1 channels, two electro-oculograms (EOG) (left inferior epicanthus/right mastoid; right superior epicanthus/right mastoid), three surface electromyographs (EMG) levator menti and right and left tibialis anterior. The patients were recommended to keep regular sleep-wake schedules with no sleep deprivation during the week preceding the sleep monitoring, but they did not complete any sleep log. Almost all of them did not take any psychotropic drugs, and the rare patients on psychotropic drug stopped them for at least 7 drug half-lives before the sleep tests. Patients arrived between 4 PM and 7 PM, were hooked, and had diner in the unit. Sleep was monitored from lights off (ad libitum, but no later than 11 PM) to lights on (ad libitum) during both nights. Patients stayed in the unit between Night 1 and Night 2, performing quiet activities including answering physicians interviews, examination and questionnaires, reading, phoning, working on their computer, or walking in the hospital garden, but were not allowed to sleep, as checked by the nurses. The slow wave activity was measured on Fp1-C3, which was not conventional but collected EEG activity of amplitude similar to the conventional F3-A2 and was exactly measured in the same way in all patients, whatever their group. Nasal pressure, tracheal sounds, chest and abdomen movements via contention belts, electrocardiogram (EKG), pulse oximeter, position, as well as synchronized ambiance sounds and infrared video. The scoring of the sleep stages was performed by trained neurologists according to standard methods [START_REF] Iber | The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications[END_REF]. The analysis of videopolysomnography included in addition the number of awakenings from stage N3 sleep over the 2 nights, as well as the corresponding observed behaviors on the video, scored by two scorers. Any abnormal behavior upon awakening in the N3 stage (opening eyes, raising head, exploring the environment with an anxious gaze, raising trunk, standing up, walking, being violent, speaking, shouting) was scored as a confusional behavior. All respiratory events were measured, including apnea, hypopnea, and flow limitation (defined as a plateau on nasal pressure lasting at least 10 sec and followed by an arousal).

Statistical analysis

Data are presented as means ± SD, unless otherwise specified. The comparisons between the patients with and without daytime sleepiness (defined as an ESS score greater than 10) were performed using Student's t-tests (quantitative measures) and chi-squared tests (qualitative measures). Pearson correlations were performed between quantitative or ordinal measures and the ESS score. All tests were two-sided and a p-value below 0.05 was considered statistically significant. All variables which achieved a p-value less than 0.15 were entered into a stepwise regression model. The computations were performed by the statistician using the SAS-V9 statistical package (SAS Institute Inc, Cary, NC, USA).

Results

Demographic and clinical characteristics of the patients

There were 158 patients (53.2% women and 46.8% men) with SW/ST, aged 32 ± 10 years (mean ± SD) at the time of the videopolysomnography, of whom 45% had frequent sleep terrors (Table 1). Among them, 74 (46.8%) had an ESS greater than 10, and 26 (16.4%) had an ESS greater than 15. There were no differences in age, sex, presence of sleep terrors, or the global severity of the parasomnia. In terms of behaviors, monthly frequency and consequences (as evaluated with the PADSS) did not differ between the groups with and without excessive daytime sleepiness (Table 1). The exclusion of item C-22 ("I am tired on the morning") from the PADSS total score and PADSS-C sub-score did not change these negative results.

- ----------------------------------------Table 1 -----------------------------------------In addition, none of the individual items of the PADSS-A and PADSS-C were different between groups, except for Item A-11 ("I handled or moved heavy objects"), which was scored more frequently in the group with vs. without sleepiness (Table 2). Item 16 ("eating food") tended to be more frequent in the patients with vs. without sleepiness.

- ----------------------------------------Table 2 -----------------------------------------

Sleep measures

During the first night, the 74 patients with excessive daytime sleepiness had shorter sleep onset latencies, and they tended to have a shorter latency to N3, and to have lower numbers of N3 awakenings than the 84 patients without excessive sleepiness (Table 3). There were no other differences in sleep measures, including markers of sleep continuity (total sleep time, sleep efficiency), architecture (percentages of sleep stages), and fragmentation (presence of any confusional behavior upon awakening from N3 sleep, number of N3 awakenings, arousal index, periodic leg movements or apnea-hypopnea). In the full group, 17 (10.7%) patients had between 5 and 15 apnea-hypopnea/h, 8 (5%) had more than 15 and less than 30 apnea-hypopnea/h, and 1 (0.06%) patient had an apnea-hypopnea index of 30.5. These percentages did not differ between groups with and without sleepiness. Only 3 patients (including 1 with sleepiness) had a periodic leg movement index greater than 15.

- ----------------------------------------Table 3 -----------------------------------------During the second night (Table 3), completed in 124/158 patients, the 57 patients with excessive daytime sleepiness had shorter sleep onsets and REM sleep latencies, longer total sleep times, higher REM sleep percentages, and a lower difference between total sleep time on Night 2 and Night 1 (a variable that we suggested to be linked to previous sleep debt) than the 67 patients without excessive daytime sleepiness. As expected by first night effects, the latencies to sleep onset, N3 and REM onsets were longer in the first than in the second night, whereas total sleep time as well as N2 and REM sleep percentages were shorter in the first than in the second night.

Determinants of daytime sleepiness

The ESS was higher when the sleep onset latency at night was shorter on Night 1 (r = -0.19; P = 0.02) and on Night 2 (r = -0.28; P = 0.002), when the latency from sleep onset to N3 sleep was shorter on Night 1 (r = -0.2; P = 0.012) and on Night 2 (r = -0.2; P = 0.03), when the latency to REM sleep was shorter on Night 2 (r = -0.19; P = 0.03) but not on Night - ----------------------------------------Table 4 ---------------------------------------- The high frequency (46.8%) of patients with excessive daytime sleepiness among adult sleepwalkers found here corroborates recent observations in large groups of sleepwalkers, which have also reported that 41-47% of patients had ESS greater than 10 [5, 6, 8]. This frequency was systematically higher than the frequency in age-matched healthy controls [START_REF] Lopez | Functional impairment in adult sleepwalkers: a case-control study[END_REF][START_REF] Oudiette | Dreamlike mentations during sleepwalking and sleep terrors in adults[END_REF][START_REF] Desautels | Daytime somnolence in adult sleepwalkers[END_REF]. Because it exceeds the 10% of naturally hypersomnolent subjects found in the generally healthy population [START_REF] Johns | Daytime sleepiness and sleep habits of Australian workers[END_REF][START_REF] Parkes | The clinical diagnosis of the narcoleptic syndrome[END_REF], this high frequency could not result from an overlap between natural hypersomnolence and sleepwalking. Sleepiness in our sleepwalkers group was not linked to age, gender, arousal index, wakefulness after sleep onset, periodic leg movements, or sleep-disordered breathing, as already observed in a smaller group [START_REF] Desautels | Daytime somnolence in adult sleepwalkers[END_REF]. More surprisingly, it was not associated either with more severe forms of the parasomnia (as measured by the frequency of SW/ST episodes, the complexity of nocturnal behaviors or their association with injuries), or to specific forms including some degrees of sleep terrors, sleep-related eating disorder or sexsomnia. Another group even finds that sleepiness is more frequent in sleepwalkers with infrequent than frequent episodes [START_REF] Lopez | Functional impairment in adult sleepwalkers: a case-control study[END_REF]. One may argue that patients with SW/ST have the greatest difficulty in evaluating the frequency of their episodes, because most of them are not recalled, making the correlation between SW/ST frequency and sleepiness less reliable. However, we do not find either a correlation between the number of awakenings in N3 sleep or the presence of confusional behaviors on videopolysomnography (which are more objective makers than selfevaluation of the number of parasomnia episodes, at least during here two nights), and the daytime sleepiness. The number of awakenings in N3 is one of the determinants of the level of sleepiness in the final statistical model, but in an inverse direction than expected (lower number, higher sleepiness). An exception is the behavior of handling heavy objects, which is more frequently reported by sleepy than non-sleepy sleepwalkers (with some difficulties in interpreting this finding) and a trend for sleepy patients to display more frequently sleepeating related behaviors. In our preceding study, we focused on 15 patients with sleep-eating related disorders; these patients were more sleepy than healthy controls and tended to be more sleepy than sleepwalkers [START_REF] Brion | Sleep-related eating disorder versus sleepwalking: a controlled study[END_REF]. However, these small differences between sleepy and nonsleepy sleepwalkers regarding amnestic handling and eating behaviors disappear in the general model, suggesting that they are dependent upon other sleep characteristics.

Several sleep measures were different here between the sleepy and non-sleepy groups, contrary to the preceding study performed in 70 French Canadian patients, which found no polygraphical markers associated with daytime sleepiness (even using spectral analysis, which was not performed here), but used a smaller sample [START_REF] Desautels | Daytime somnolence in adult sleepwalkers[END_REF]. These measures included shorter sleep onset latencies (a link repeated during the two nights), a shorter latency to REM sleep, a longer total sleep time and a higher REM sleep percentage in Night 2. If none of these measures are linked to the N3 sleep (the stage from which the parasomnia arises), they coherently indicate a propensity to fall asleep (more rapid sleep and REM sleep onsets) and to show prolonged sleep (as shown by longer sleep time, which is usually associated with longer REM sleep). Longer sleep time in sleepy patients during Night 2 does not result from previous sleep deprivation (a strong trigger of sleepwalking episodes) [START_REF] Zadra | Polysomnographic diagnosis of sleepwalking: effects of sleep deprivation[END_REF], because it is observed on the second and not on the first night, and because there are no differences between sleep times on Night 1 Night 2, in contrast to non-sleepy patients who exhibited a longer sleep time on Night 1 than on Night 2. All in all, these results suggest that sleepiness in sleepwalking is not caused by sleep deprivation or fragmented sleep (via arousals, upper airway resistance, or N3 awakenings), but is, on the contrary associated with a phenotype of "good sleeper" falling rapidly asleep, and sleeping for a long time. This phenotype suggests a higher sleep propensity in sleepwalkers with than without sleepiness (close to the hypersomnolence of central origin), which could be a genuine subtype of sleepwalking. One may even imagine that this higher sleep pressure and subsequent sleepiness is not a consequence but one of the causal mechanisms of SW/ST in vulnerable subjects. Indeed, subjects with higher sleep pressure would have more difficulties waking from N3, possibly resulting in a partial rather than a complete arousal from N3, leading to this hybrid state of half-wake/half-sleep which characterizes SW and ST [START_REF] Terzaghi | Evidence of dissociated arousal states during NREM parasomnia from an intracerebral neurophysiological study[END_REF]. Such hypotheses cannot explain why these people awake from N3, but rather how they awake. As we did not perform a spectral EEG analysis, it is not possible to evaluate whether the homeostatic sleep drive is intact or increased in sleepy vs. non-sleepy sleepwalkers. The heritability of sleepwalking is high, especially in adults [START_REF] Hublin | Prevalence and genetics of sleepwalking: a population-based twin study[END_REF], and a genetic locus for sleepwalking has been found at chromosome 20q12-q13.12 in a multiplex family [START_REF] Licis | Novel genetic findings in an extended family pedigree with sleepwalking[END_REF], suggesting that allelic variants may underlie the presence of sleepwalking and sleep terrors. Once these variants will be found, it will be interesting to study whether they are different in sleepy vs. non-sleepy patients.

Conversely, it will be also interesting to observe whether the "sleepy" phenotype of SW/ST has a familial aggregation too.

This study contains several limitations inherent to any retrospective collections of clinical and polygraphical measures. Only 75% of patients completed the PADSS, but their number (n=118) was sufficient to provide robust analysis of correlation with ESS. Similarly, 78% of patients underwent two consecutive nights, but their number (n=124) was again sufficient to provide robust analysis. There were no specific questionnaires evaluating insomnia, depression (a frequent cause of sleepiness) or anxiety, but anxiety and mood disorders were screened by the physician in charge, and the answers on Item 23 of the PADSS-C (which evaluates the degree of shame, anxiety, fear to go to sleep or any psychological association with the parasomnia) were similar between patients with and without sleepiness. The level of sleep deprivation was not measured using sleep log or (even better) actigraphy during the week preceding the videopolysomnographies. Patients were however recommended to keep regular sleep-wake schedule before the test, and we used a surrogate measure of sleep deprivation, which indicated no sleep deprivation in the sleepy patients, in contrast to the non-sleepy patients. Eventually, sleepiness was measured using the ESS, and not with objective measures of sleepiness or alertness (including multiple sleep latency test, which may not be enough sensitive to capture the sleepiness problems in patients with SW/ST [START_REF] Lopez | Objective daytime sleepiness in patients with somnambulism or sleep terrors[END_REF], maintenance of wakefulness tests, attention tests). All these measures have their own interest and do not measure exactly the same thing [START_REF] Chervin | Epworth sleepiness scale?[END_REF]. The Epworth sleepiness scale remains a robust measure of self-perceived sleepiness, which is what disturbs the patient.

In conclusion, sleepiness in SW/ST is not the consequence of disturbed sleep but is, on the contrary, associated with a specific polygraphic phenotype (rapid sleep onset, long sleep time, lower awakenings in N3), suggestive of a higher sleep propensity, which may contribute to the imperfect awakenings from N3 characteristic of SW/ST. This frequent subtype of sleepwalking would be worth studying in terms of genetics.

1 ,

 1 and when the total sleep time on Night 2 was higher (r =0.22; P =0.014). The ESS did not significantly correlate with any other clinical variables (age, severity of parasomnia as assessed by each sub-score of the PADSS as well as the total score) or measures of sleep duration (total sleep time during the two nights, sleep efficacy, wakefulness after sleep onset), architecture (percentages and duration of sleep stages), fragmentation (number of arousals/awakenings in N3 sleep, arousal index, apnea-hypopnea index, periodic leg movements index) or an indirect marker of sleep deprivation (difference of N3 between Night 2 and Night 1). Similarly, categorical measures of demography (sex), clinical aspects (score at each descriptive item of PADSS-A, presence of sleep terror) and videopolygraphical aspects (presence of abnormal behavior during N3 awakening, presence of intense adrenergic reaction upon N3 awakening) did not predict any change in ESS.

-

  All measures with a P < 0.15 were entered into a stepwise regression model, including sleep onset latencies on Nights 1 and 2, N3 latencies on Nights 1 and 2, total sleep time on Night 2, plus sleep efficacy on Night 1 (r = 0.14; P =0.086), and the number of awakenings in N3 during Night 1 (r = -0.14, P = 0.09). The final model is indicated in Table3. The level of sleepiness was determined by the sleep onset latency on Night 1, the number of awakenings in N3 on Night 1 and the total sleep time on Night 2.4. DiscussionAlmosthalf of the 158 adult patients with sleepwalking and sleep terrors reported excessive daytime sleepiness. They had shorter sleep onset latencies (in Night 1 and Night 2), shorter REM sleep latencies, longer total sleep time and higher REM sleep percentages in Night 2 than patients without sleepiness. Similarly, the level of sleepiness correlated with the same measures (sleep onset latency in both nights, REM sleep onset latency and total sleep time in Night 2), plus the latency to N3. The final regression model indicated that the level of sleepiness was determined by the sleep onset latency on Night 1, the number of awakenings in N3 on Night 1 and the total sleep time on Night 2.

Table 1

 1 Clinical characteristics of patients with sleepwalking and sleep terrors, with and without

	excessive daytime sleepiness
		All patients	With	Without	P
			sleepiness	sleepiness
	N	158	74	84
	Age, y	32.8 ± 9.9	33.6 ± 9.8	32.2 ± 10.1	0.37
	Gender, % men	47.6	43.2	50	0.43
	ESS score, 0-24	9.8 ± 5.4	14.3 ± 3.1	5.8 ± 3.1	<0.0001
	Clinical severity of the parasomnia
	N	118	48	62
	Sleep terrors, %	45	46.9	43.4	0.73
	Total PADSS, 0-50	17.4 ± 5.3	18.1 ± 4.5	16.9 ± 5.8	0.26
	PADSS-A, 0-34	9.0 ± 5.0	9.8 ± 5.2	8.3 ± 4.7	0.09
	PADSS-B, 0-6	4.2 ± 1.1	4.3 ± 1.0	4.1 ± 1.1	0.32
	Number of	17.4 ± 21.8	20.1 ± 22.6	14.8 ± 20.7	0.21
	episodes/month
	PADSS-C, 0-10	3.7 ± 1.5	3.8 ± 1.4	3.7 ± 1.7	0.59

ESS: Epworth sleepiness scale; PADSS: Paris arousal disorder sleepiness scale.

Table 2

 2 Behaviors during sleepwalking and sleep terrors in patients with and without excessive

	daytime sleepiness
	PADSS-A, % patients with positive answer	With	Without	P value
		sleepiness	sleepiness
	I screamed	93.5	84.6	0.10
	I sat up in my bed	95.7	87.7	0.48
	I hit or kicked someone or something,	72.3	64.1	0.50
	I fell out of bed	38.3	41.3	0.76
	I went out of my room	72.3	69.2	0.40
	I went down or up the stairs	34.1	30.2	0.87
	I went out of my home	14.9	17.2	0.83
	I opened a window	42.6	30.8	0.23
	I climbed out a window	12.8	10.9	0.57
	I handled or moved light objects (slippers, small	61.7	58.5	0.26
	things)
	I handled or moved heavy objects (lamp, vase,	44.7	28.1	0.02
	furniture)
	I broke an object, window, or wall	23.4	30.8	0.48
	I picked up sharp objects (knife, tools)	6.3	6.4	0.97
	I manipulated objects that may set a fire (matches,	2.1	1.6	0.82
	lighter, gas stove, oven)
	I touched things around windows and openings	48.9	47.7	0.49
	(blinds, shutters, curtains, window/door handle)

Table 3

 3 Sleep characteristics in patients with sleepwalking/sleep terrors, with and without excessive

	daytime sleepiness
		All patients	With	Without	P
			sleepiness	sleepiness
	Night 1, n	158	74	84
	Latency to, min
	Sleep onset	33.8 ± 31.8	26 ± 21.1	41.1 ± 37.8	0.002
	N3 sleep	53.3 ± 38.5	46.8 ± 36.8	58.5 ± 39.7	0.06
	REM sleep	140.5 ± 78.7	142.3 ± 80.4	134.3 ± 74.5	0.47
	Total sleep time, min	469.1 ± 93.6	461.5 ± 96.5	477.5 ± 92	0.29
	Sleep efficiency, %	86.5 ± 8.5	87.6 ± 8.2	85.5 ± 8.8	0.13
	Duration of stages (% of
	total sleep time)
	N1	4.3 ± 3.5	4.2 ± 3.4	4.4 ± 3.6	0.73
	N2	51.1 ± 8.7	51.6 ± 8.2	50.3 ± 8.8	0.35
	N3	25.2 ± 9.1	25.4 ± 9.3	25.2 ± 9.1	0.90
	REM	19.5 ± 7.5	18.7 ± 5.7	20.5 ± 8.7	0.13
	Awakenings from N3
	Number	5.4 ± 3.4	5.0 ± 3.0	5.9 ± 3.7	0.09
	Confusional behavior,	82.3	81.8	82 .7	0.64
	% patients with
	Intense adrenergic	69.1	69	69.1	1.00
	reaction, % patients with

*Estimated via the difference of N3 sleep between Night 1 and Night 2, assuming that highest values correspond to the compensation of a more important previous debt.

Table 4 -

 4 Model predicting the presence of sleepiness in patients with sleepwalking and sleep

	terrors
	Effect	DF	Estimat	Standard	Wald Chi	P	Point
			e	Error	Square		Estimat
							e
	Intercept	1	-1.254	1.27	0.97	0.33
	Sleep onset latency (Night	1	-0.199	0.09	4.99	0.03	0.82
	1)
	Number of awakenings in	1	-0.126	0.06	4.43	0.04	0.88
	N3 (Night 1)
	Total sleep time (Night 2)	1	0.529	0.255	4.31	0.04	1.70

Financial Disclosure Statement

This is not an industry-funded study. It was performed as part of the normal work of the participants.

Author contribution

The patients were diagnosed (clinical diagnosis and scoring) and followed up by IA, SLS and EG. The measures were collected by MCS, who prepared the tables and figures. JLG performed the statistics. IA wrote the article, which was reviewed and approved by all authors.

Conflict of interest

The authors have no conflict of interest related to the study. Professor Arnulf received an honorarium from UCB Pharma for speaking engagements and consultancy. Dr. Leu-Semenescu had her congress fees paid by UCB Pharma. These financial disclosures are unrelated to the present study and topic. Drs. Carrillo-Solano and Golmard have no conflicts of interest to disclose.