The Re-make as (Dis)avowal:

The Ambivalent Stances of the Hollywood Blockbuster Horror Remakes of the 2000s 1 David Roche, Université Toulouse Jean Jaurès Keywords: remake, horror, stance, disavowal, improvement, technique, technology, The Texas Chain Saw Massacre (1974), The Texas Chainsaw Massacre (2003), Texas Chainsaw 3D (2013), Tobe Hooper, Thomas Leitch, Marcus Nispel, John Luessenhop The prefix "re-" says it all, both the motive for, and the means of, remaking a film: you do it for a profit and you do it by improving on the original in terms of technology and technique. As Daniel [START_REF] Protopopoff | Du cinéma comme bibliothèque idéale[END_REF] have pointed out, remakes "benefit from the technical improvements of cinema," such as "stereophonic sound, wide screens" or "color" (26, my translation). They are also thought to improve in other respects that can equally be considered in terms of technique: the quality of the acting, the effectiveness of the narration, and ultimately, by Hollywood standards, the degree of verisimilitude. 2 This article will attempt to foreground some of the contradictions immanent to the remake. I will argue that the stance of the remake is a disavowal of the very terms contained in the prefix. I am heavily indebted to Thomas Leitch's (1990[START_REF] Leitch | Twice-Told Tales: Disavowal and the Rhetoric of the Remake[END_REF] argument that the remake is grounded in a "trope of disavowal," a stance which, in my view, is both formal and pragmatic, involving both the film itself and the way it is marketed by producers and received by audiences.

1 Some of the ideas have appeared in Making and Remaking Horror in the 1970s and 2000s. 2 The cast and crew of contemporary remakes often emphasize this aspect (Roche 278). For instance, in the DVD extra "Surviving the Dawn," actor Jake Weber says that Dawn of the Dead (Zack Snyder, 2004) tries to "play it a little closer to the vest [than Dawn of the Dead (George A. Romero, 1978)], and make it more about real people, and what would we do if we woke up and the world went mad" [2:50].

Michael B. [START_REF] Druxman | Make It Again, Sam: A Survey of Movie Remakes[END_REF] and Harvey Roy [START_REF] Greenberg | Raiders of the Lost Text: Remaking as Contested Homage in Always[END_REF] have proposed the following typologies of the remake: 3 Druxman distinguishes between "the direct remake," "the disguised remake" and "the non-remake" ; Greenberg between "the acknowledged, close remake," "the unacknowledged, disguised remake" and "the acknowledged, transformed remake" (126). For Constantine Verevis, Druxman's approach to classifying remakes is "commercially grounded," while Greenberg's is more "authorial" (8). What Greenberg mainly does is add the discourse of producers, critics and viewers to Druxman's commercial and formal classification. The usage of the word "acknowledge" invites us to take into account both the film and the paratext (posters, production notes, interviews, DVD extras), and more generally, the formal and pragmatic levels.

Thomas Leitch has identified four "stances" of the remake vis-à-vis its source material ("Twice-Told" 45), without making it absolutely clear whether these "stances" are pragmatic, formal or both; this is largely due to the fact that he provides few examples to illustrate his claims. Leitch's four stances include the "readaptation" and the "update" which involve different attitudes towards the adaptation of a previously adapted literary work ("Twice-Told" 45, 47), and the "homage" and the "true remake" which imply different attitudes towards an original film. The "homage" pays tribute to a classic ("Twice-Told" 47) and "renounc[es] any claim to be better" ("Twice-Told" 49), while the "true remake" "combines a focus on a cinematic original with an accommodating stance which seeks to make the original relevant by updating it" ("Twice-Told" 49);; Leitch specifies that "the producers of the [true] remake wish not only to accommodate the original story to a new discourse and a new audience but to annihilate the model they are honoring-to eliminate any need or desire to see the film they seek to replace" ("Twice-Told" 50). The "true remake" would, then, appear to be more ambivalent than the "homage," since it both honors and effaces.

The idea that the remake seeks to annihilate the original film is fairly common in writings about Hollywood remakes of foreign films. Raphaëlle Moine (2007) has argued that films like Cousins (Joel Schumacher, 1989) and Three Fugitives (Francis Veber, 1989) attempt to erase the original French films, while Sébastien Rongier (2007) has gone even further by saying that any remake is "the construction of an erasure" (161). It is, however, doubtful that the erasure is ever that total, seeing as 3 Protopopoff mainly considers remakes in terms of their source material: a film, a piece of literary fiction, or both (17).

Hollywood often asks the original directors-Francis Veber for Three Fugitives or more recently Takashi Shimizu for The Grudge (2004)4 -to direct the remakes of their own films. Moreover, some of the original films have been successful among American niche audiences of foreign films and/or horror movies. In 1999, Le Dîner de cons (Francis Veber, 1998) grossed $4 million by the end of 1999, a fair amount for a foreign film in the U.S., although, granted, nothing compared to the $73 million grossed by Dinner for Schmucks (Jay Roach, 2010) in 2010. 5 In any case, Constantine [START_REF] Verevis | Film Remakes[END_REF] has proven since that remaking is not always synonymous with erasure. By resorting to the term "pre-sold title," he draws attention to the fact that it is often in the producers' interest that they acknowledge that their film is a remake of a well-known film. This is especially the case of Hollywood remakes of domestic films. On the official film websites and later in the DVD extras, "filmmakers often enthuse about the 'timeless' attributes and 'classic' status of originals before going on to insist upon their own value-added transformations" (Verevis 17). Furthermore, the economic relationship between original and remake does not just go one way, as the original film often benefits from the release of the remake; DVD releases of the original movies frequently come out the same year as the remake, and they can often be "found side by side on the shelves of rental outlets" in the U.S. or on the web (Verevis 12). Generally speaking, it would seem then that Hollywood producers remake foreign films in order to exploit a narrative that has proven successful, but that when remaking domestic films, they are just as much tapping into the associations the original film evokes in popular culture. Thus, exploiting a "pre-sold title" and a successful narrative need not go hand in hand: a close remake like Quarantine (John Rick Dowdle, 2008) does not maintain the original title, whereas a non-remake, like Prom Night (Nelson McCormick, 2008), that merely maintains the basic premise of the original, does. Respect and acknowledgment do not necessarily imply fidelity to the original narrative, as Greenberg's typology rightly indicates;; Verevis has noted that contemporary remakes are increasingly non-remakes, "with all new characters, settings and situations" (22).

If the producers want the audience to know that the remake is based on a previous film as a guarantee of the remake's quality, it is equally doubtful that they care whether viewers actually watch the original film. This is where Leitch's two stances come into play: the "homage" presupposes that the remake should be viewed alongside the original; the "true remake" presupposes that the remake should be viewed in place of the original. Leitch With the "true remake," however, technique and technology are instrumental in accomodating and updating the original. Thus, the "true remake" is somewhat steeped in a teleological faith in progress, the "homage" in nostalgia. In the end, both stances are very ambivalent about the remaking process. The "homage" renounces improving on the original but remakes it anyway, while the "true remake" rests, as Leitch has noted, on the "paradoxical promise" that it is "just like its model, and that it's better" ("Twice-Told" 44)-Leitch's use of "and" here is paramount. Leitch then calls on the "trope of disavowal" in order to delineate the "dance of invocation and denial" typical of the remake ("Twice-Told" 52). For Leitch, avowal is immanent to disavowal: Disavowal-that is, the combination of acknowledgement and repudiation in a single ambivalent gesture-is apt in far more specific ways to the remake's model of intertextuality, since remakes by definition establish their value by invoking earlier texts whose potency they simultaneously valorize and deny through a series of rhetorical maneuvers designed at once to reflect their intimacy with these earlier texts and to distance themselves from their flaws. ("Twice-Told" 53) This disavowal, produced by "rhetorical maneuvers" that are both formal and paratextual, concerns not only aesthetics-the extent to which the remake assumes its intertextuality, starting with its own relationship to the original, but also including its relationship to other films, including future remakes-but also technique and technology, insomuch as the idea that the remake can improve on the original inscribes its own future obscolescence within the remaking process. In short, the remake's disavowal involves the extent to which the remake assumes the prefix "re-."

The blockbuster remakes of domestic horror films Hollywood has been dishing out for the past ten years provide a welcome corpus for a study of the remake's ambivalent "stance." This cycle includes remakes of films, mainly from the 1970s and 1980s,7 that were both independent low-budget films like The Texas Chainsaw Massacre (Tobe Hooper, 1974;Marcus Nispel, 2003) and major Hollywood productions like The Omen (Richard Donner, 1976;John Moore, 2006); films that were box office hits like Halloween (John Carpenter, 1978;Rob Zombie, 2007) and others that were fairly unsuccessful like My Bloody Valentine (George Mihalka, 1981;Patrick Lussier, 2009); films that have received much critical attention like Dawn of the Dead (Romero, 1978;Snyder, 2004) and others that have gone ignored like House on Sorority Row (Mark Rosman, 1983;Stewart Hendler, 2009). In short, this cycle has homogenized a fairly heterogeneous body of films, something which a comparative study of their aesthetics confirms-for instance, the remakes tend to resort to typical slasher film strategies and their music scores are almost identical . Bigger budgets enable the producers to hire well-known actors, often from TV series (Roche 292), use 35mm or digital cameras and Dolby Digital sound, and resort to more sophisticated special effects, including CGI and 3D for the more recent remakes like My Bloody Valentine 3D (Patrick Lussier, 2009) or Piranha 3D (Alexandre Aja, 2010).

The motivation for remaking some of these films has often less to do with the quality or availability of the narrative than with the familiarity of their titles. Many of the remakes are, in effect, non-remakes that tend to reprise the same premise-a psychokiller stalking the prom, a sorority house or a graduation party-but modify the characters and situations to the extent that, in some cases, they probably would not even need to secure the rights of the original film if it were not that they wanted to use the title. Yet, if cultural memory seems more economically viable than the individual spectator's, these remakes ultimately tap into both. Many of them play on expectations of the fans of these cult movies by altering the outcome in order to provide a different answer to the original whodunnit; this is the case of films like Prom Night (2008) which takes up the false lead of Prom Night (Paul Lynch, 1980), and My Bloody Valentine 3D (2009) which switches the hero and the killer of My Bloody Valentine (1981). Even remakes of lesser known films will recycle a famous scene from the original. This is the case in Silent Night (Steven C. Miller, 2012) where one of the victims is impaled on some decorative antlers. Of course, this reference works on two levels: if the reference to Silent Night, Deadly Night (Charles E. Sellier, Jr., 1984) were lost to some viewers, other horror movie fans would, no doubt, identify the original reference to the famous meat hook scene since the original scene was already a reimagining of the famous meat hook scene from the classic The Texas Chain Saw Massacre (1974).

So however small the fan base of a given movie is, the remakes never fail to address them, probably because they realize that those members of the audience are even more active on internet than mainstream audiences. My impression is that the American horror remakes of the 2000s are targeting three types of audiences: (1) older fans of the genre who know the original and will go and see the remake out of a nagging curiosity; (2) younger fans of the genre who may or may not have seen the original, but could be interested in seeing Rob Zombie's latest film;; and (3) wider audiences who will pick the remake because they are in the mood for a horror movie and the title may ring a bell (Roche 17). I suspect that the viewers who are more likely to discover the original after seeing the remake would belong to the second category. My hunch is that, although the filmmakers address the first two categories in the interviews and DVD extras, the budgets of the remakes are a clear indication that the remakes are mainly aimed at the third category, which is necessary to make a profit on opening weekend and immediately make up for production costs. In this respect, the rhetoric of address in the paratext of the remakes is largely a denial of the remake's economic terms: the paratext is aimed at the midto long-term audience, that is fans of the horror genre, when the remake, like any film, is just as determined (if not more so) to bank on an immediate neophyte audience. As Leitch has pointed out, "most remakes do their best to satisfy" all audiences ("Twice-Told" 41). I would add that this is in keeping with Hollywood policy to avoid alienating potential consumer groups, even if this means producing "consciously ambivalent and ambiguous" films (Elsaesser 99).

I would like to turn to a case study of the "stance" of the remake that started the proclaim that the original is a classic, 9 and director Marcus Nispel even admits he was "scared" Tobe Hooper would not like the remake when he met him at the premiere. 10 Yet if the producers hired a screenwriter who was a fan of the original, they hired a director who worked in music videos, confessed to his lack of familiarity with the genre and had never even seen the original film.11 Though the paratext addresses fans of the genre and of the original film, the industrial terms of the blockbuster clearly target more mainstream audiences. Indeed, the producers conducted "research showing that 90% of the film's anticipated core audience (eighteen to twenty-four year old males) knew the title of Tobe Hooper's original but had never seen it" (Verevis 134);; significantly, they retained the popular spelling of the title rather than the original title with "chainsaw" in two words.

Apart from a few scattered shots like the lateral establishing shot in which the teenagers' van appears to be crushed under the empty Texas sky, the 2003 remake's "stance" is mainly established in the opening shots, which is fairly typical of remakes (Leitch, and comic book adaptations [START_REF] Boillat | L'effet BD à l'ère du cinéma en images de synthèse : Quand les adaptations filmiques de comic books se risquent à signifier la fixité de leur modèle dessiné[END_REF]. The 1973-Texas (2003) ) indicates that both films tell the same story, but the evidence it supplies invalidates the "veracity" of the earlier film. Whereas the 1974 voiceover and intertitle merely state that the event is "one of the most bizarre crimes in the annals of American history," Texas the victim's name (Morgan) on the "evidence" sticker [1:25], and the scratch marks on the staircase wall identified by the policeman during the crime scene walk-through [2:10]. These images, items and events reappear in the course of the film [4:20, 46:00, 76:15]. In other words, the images, more than the voiceover, are supposed to provide proof that Texas (2003) is giving us the "real" story;; the shot of the "case study" written by a doctor and entitled "The Texas Chainsaw Massacre" even justifies the change the filmmakers brought to the spelling of the title [2:35]. The juxtaposition of black-and-white and color images, and the voiceover are highly reminiscent of sensationalist TV docudramas like A Current Affair (1986Affair ( -1996)), with the archive footage seemingly providing the underpinning for the reconstitution of real events that is the main bulk of Texas (2003).

The voiceover's stopping during the police crime scene walk-through would tend to confirm the idea that the images speak for themselves. Yet, on the contrary, the images, which started before the voiceover, are only retroactively constituted as "evidence" by the voiceover thirty seconds into the film. In other words, the voiceover is necessary to present these images as "real" as opposed to fictional. This brings to mind Susan Sontag's comments on the relationship between a photograph and its caption, that is, that "the contribution of photography always follows the naming of the event" (19). Thus, the voiceover invokes the original, the images deny the original, but the denying images require the invoking voiceover in order to deny, thereby undermining the denial. The generous budget of Texas (2003) allows it to mimic the technology of the 1970s and erase the 1974 film, yet ultimately, it is the slightly modified 1974 voiceover that legitimizes its technological maneuver. All the more so as the "authenticity" of the images is called into question halfway through the film.

Indeed, the archive footage, that was meant to legitimize the main body of the film, is revealed to be a fabrication halfway through the film, when the second establishing shot of the Hewitt house reveals that the black-and-white shot of the house in the opening credits was, in fact, a smaller version of the same shot [41:05].

Texas Chainsaw 3D (2013) was clearly marketed as a sequel to the 1974 film. As such, it ignores the 2003 remake and replaces-or remakes-the 1986 and 1990 sequels to the 1974 film. Like some remakes, the producers sought legitimacy by seeking support from the producers of the 1974 film (Kim Henkel and Tobe Hooper).

The official website even displays Hooper's stamp of approval-"INCREDIBLE! A PERFECTLY TERRIFYING FOLLOW-UP TO THE ORIGINAL"-while another section devoted to the cast and crew includes lengthy bios of actors Marilyn Burns and Gunnar Hansen. Yet though the 2013 sequel appears to acknowledge exclusively the 1974 film, its terms are not as straightforward as might seem at first.

The posters by no means indicate that the film's a sequel, and the title is somewhat misleading. The absence of the words "The" and "Massacre" seem to indicate that it is not a remake, yet the absence of "2," "Part II," or a subtitle like "Forty Years Later" gives no indication as to its being a sequel. In fact, the shortened version of the original title recalls the shortened version fans sometimes use in fanzines, on blogs and bulletin boards,12 so that the usage of "3D" in place of "Part II" gives the overall impression that we are going to watch the 3D version of Texas Chainsaw, aka The Texas Chainsaw Massacre. Once again, the title is meant to attract a wider audience than the teasers, websites and DVD extras would suggest, an audience that would go see the film on the sole basis of their familiarity with the pre-sold title and an opportunity to watch a technologically updated version of a classic film.

The prologue of Texas Chainsaw 3D (2013) confirms this seemingly straightforward and yet absolutely incoherent stance. It opens with a voiceover, this time the heroine's panic-stricken voice, recycles some of the sound effects, notably the zinging sound and some low ominous notes, and reprises a series of shots from the 1974 film-the swing, the windmill, the attacks on Kirk, Pam, Jerry and Franklinin the order they appear in the 1974 narrative [0:25]. However, the selection process somewhat rewrites theses scenes. For instance, Pam's discovery of the room with the macabre furniture is eliminated so that Leatherface's attack on her appears sudden, an impression reinforced by the addition of a high-pitched note to provoke a startle effect. The 1974 film has been remade into a contemporary slasher, 13 replete with edgy editing. The 2013 prologue modifies not only the tone of the 1974 film, but also some of the diegesis. Digital technology is employed to replace actor Jim Siedow, who played Old Man in Texas (1974), with another actor, Bill Mosley, who played another part (Chop-Top) in the 1986 sequel and who is here renamed Drayton [2:15]. This is justified by the fact that this character is in the 2013 sequel's first scene, a showdown at the Sawyer house inspired by the beginning of The Devil's Rejects (Roz Zombie, 2005). There is no justification, however, for renaming the 1974 Sally Sarah.

So the foggy frame utilized in the 2013 prologue does, in effect, materialize the distance the 2013 sequel establishes between itself and the 1974 film, a distance that is reinforced by the use of 3D. Though the 2013 sequel claims to be a sequel to the 1974 film, it is also a reboot, and thus a remake, as many viewers have noticed. The Texas Chainsaw Massacre films show how ambiguous and similar the stances of the remake and the sequel/reboot ultimately are because avowal and recognition are ultimately immanent to disavowal and disregard. Though remakes are inevitably caught in an intertextual web, I would, however, caution against equating the remake with intertexuality, which is what Verevis tends to do. I would argue, rather, for an approach to the remake (and to adaptation) similar to what Rick Altman proposes for film genre. Pragmatically, remakes are films that have been identified as such by their producers and/or audiences. The decision whether or not the film is a remake can change in time: hence, viewers and critics may decide that a film marketed as a remake is, in fact, a "non-remake," while an instance of plagiarism is, in fact, a remake. The case of the Hollywood remakes of domestic horror films provides ample proof that one cannot just propose a taxonomy of the remake in an end note as if it were unproblematic, or satisfy oneself with a monolithic view of the remake as erasure. Leitch himself must have felt ill-at-ease with his usage of the adjective "true" in his discussion of various stances, since it disappears over the course of his article where the term "remake" ends up standing alone. Even when it poses as an "homage," the stance of the remake is fundamentally ambivalent, for it recognizes the value of the original, sometimes even legitimizing it, thereby expressing faith in the values of the past, yet proposes to make it relevant, notably through technique and technology, thereby expressing a faith in progress. In so doing, however, it simultaneously binds itself with the original intertextually and often commercially-and thus fails to sever all ties in spite of technique and technology15 and inscribes its own future obsolescence within the process-and thus establishes new ties with the original as a consumer product because of technique and technology. In this respect, the remake is paradigmatic of contemporary marketing strategies: like various home appliances we warily acquire, the remake banks on its brand to make money, but is made to last a limited time only.

Filmography

The

  's stances thus indicate two very different views of the relationship between remaking and technique. With the "homage," technique is not seen as an improvement since the original cannot be improved on in the first place. The whole point of Psycho (Gus van Sant, 1998), as Dominique Sipière has noted, is to view the two films side by side and see what choices Gus van Sant made, notably regarding the usage of color (Sipière 253). In other words, the "homage" often becomes what Leitch calls in his book on adaptation-and let us not forget that remakes are a form of adaptation (Protopopoff 17; Hutcheon 170)-a "revision," i.e., a study and/or critique of the original (Adaptation 108); 6 this is notably the case of Bram Stoker's Dracula (Francis Ford Coppola, 1992) which claims to faithfully adapt the source novel, yet taps just as much into the intertexual network of Dracula and vampire films.

  cycle of Hollywood remakes of American horror movies of the 1970s and 1980s, The Texas Chainsaw Massacre(Marcus Nispel, 2003), and at the way the recent release of Texas Chainsaw 3D(John Luessenhop, 2013) has made the 2003 remake simultaneously redundant and significant. Texas (2003) is a clearly "acknowledged" remake, but it has been fairly transformed. It keeps the basic narrative-five teenagers traveling in a van fall into the hands of a psychotic family-the geographical and temporal setting-Texas in 1973-and key motifs-the hammer, the meat hook and the chainsaw-but it adds a contemporary frame story which relates the disclosure of documents thirty years after the events, and invents new characters with different names; only Leatherface gets to keep his, the name obviously belonging to cultural memory just as much as the movie's title. With a budget of less than $100,000, Texas (1974) was shot in 16mm and blown up to 35mm, had unknown actors, a mono sountrack and a limited number of special effects, much of the violence being suggested through the editing and the sound effects. With a budget of over $9 million and Pearl Harbor (2001) director Michael Bay producing, Texas (2003) was shot in 35mm, with actors who have starred in successful TV series-Jessica Biel from 7th Heaven (1996-2006) and Eric Balfour from Six Feet Under (2001-2003)-or even auteur films-R. Lee Ermey from Full Metal Jacket (Kubrick, 1987)-and sophisticated special effects that enabled the film to indulge in high levels of gore. Hiring the cinematographer of the original film (Daniel Pearl), who was just starting out in 1974, is, perhaps, the clearest indication of the producers' ambivalent enterprise: his presence guarantees that they are making the "same" movie-he even claims they used the same technique for the meat hook scene 8 -only "better," since he now has more experience and knowledge of the technology of cinema. A study of the abundant material on the DVD of Texas (2003) sheds further light on the producers' ambivalent, not to say incoherent, discourse. They repeatedly 8 On the DVD commentary "L'équipe technique" [78:40].

  2003 prologue both revisits and expands on the 1974 intertitle and opening voiceover. The most obvious homage to the 1974 film involves the voiceover: the same sentence is spoken by the same actor, John Laroquette [0:40]. Or almost. To start with, the names of the main protagonists-which the 2003 film has changedare not mentioned. The second major modification made to the text is the addition of "the files" that have "collected dust" "for over thirty years" and the "1,300 pieces of evidence" [1:30]. By maintaining the same time-setting as Texas (1974)-August 18,

  (2003) sets out to prove it by adding photographic images: black-and-white for the archive footage, color for the contemporary shots of the cold case division of the Travis County Police Department. The evidence includes an establishing shot of the Hewitt residence filmed in 1973 [1:00], a pair of glasses [1:05], the Mad magazine banner the teenagers have on the ceiling of the van with 9 Michael Bay in Chainsaw Redux Chainsaw Redux: Making a Massacre [8] Blair in commentaire équipe technique [2], Kosa in Commentaire audio histoire [15 :30] 10 On the DVD commentary "La production" [82:15].

Like

  Friday the 13th (Marcus Nispel, 2009), it impossibly reprises elements from the whole franchise, including the 2003 remake. Though it replaces the 1986 sequel, it nonetheless retains the family name, the Sawyers, which Hooper introduced in that film. And though it ignores the 2003 remake, it names Leatherface after the little boy, Jedidiah, the 2003 teenagers meet in the Old Crawford mill, and remakes the crimescene walk-through of the 2003 prologue [58:05]. In this scene, a distancing effect is again introduced through technology, this time diegetically, as the Super-8 camera of the 2003 prologue is now replaced with the iPhone Officer Marvin uses to film his exploration of the Miller basement, Sheriff Hooper and Mayor Hartman acting as stand-ins for the spectator. 14 Texas (2013) thwarts viewer expectations aroused by the references to Texas (1974) and (2003), first by having Officer Marvin kill Nikki who lunges at him from a chest freezer like the 1974 Pam [64:15], and then by having Leatherface attack Deputy after he has stopped filming (instead of while he's filming as in the 2003 remake) [64:45]. The recycling of yet another scene from Texas (1974) is thus doubly distanced, first by the intertextual frame provided by the 2003 remake, and secondly by the technological frame within the 2013 diegesis.

  Texas Chain Saw Massacre. Directed by Tobe Hooper. Written and produced by Kim Henkel and Tobe Hooper. With Marilyn Burns (Sally Hardesty), Allen Danziger (Jerry), Gunnar Hansen (Leatherface), Teri McMinn (Pam), Edwin Neal (Hitchhiker), Paul A. Partain (Franklin Hardesty), Jim Siedow (Old Man or Cook), and William Vail (Kirk). Vortex, 1974. DVD. Universal Pictures, 2006. The Texas Chainsaw Massacre. Directed by Marcus Nispel. Written by Scott Kosar. With Jessica Biel (Erin), Eric Balfour (Kemper), Andrew Bryniarski (Leatherface), R. Lee Ermey (Sheriff Hoyt), Erica Leerhsen (Pepper), Jonathan Tucker (Morgan), and Mike Vogel (Andy). New Line Cinema, 2003. DVD. Metropolitan, 2004. Texas Chainsaw 3D. Directed by John Luessenhop. Written by Adam Marcus, Debra Sullivan and Kirsten McCallion. With Alexandra Daddario (Heather Miller), Dan Yeagr (Leatherface), Thom Barry (Sheriff Hooper), Scott Eastwood (Carl), Tania Raymonde (Nikki), and Paul Rae (Burt Hartman) and Trey Songz (Ryan). Leatherface Productions and Lionsgate, 2013. DVD. Metropolitan Video, 2013.

Luc Besson was asked to direct the American remake(John Badham, 1993) of Nikita (1990) but turned down the offer.

Låt den rätte komma in(Tomas Alfredson, 2008) grossed over $2 million, while Let Me In(Matt Reeves, 2010) made over $12 million.

This is also the case of the usage of color in Night of the Living Dead(Tom Savini, 1990), and color and sound in Nosferatu(Werner Herzog, 1979).

This cycle was preceded by a remake of House on Haunted Hill(William Castle, 1959; William Malone, 1999), followed by House ofWax (André De Toth, 1953; Jaume Collet-Serra, 2005).

On the DVD commentary "La production" [18:20, 29:15].

See November

13, 2010 interview with Share Cherrie on <http://www.horror-asylum.com/interview/sharecherrie/interview.asp>.

This scene crosscuts with the scene where Heather looks at the evidence Sheriff Hooper has kept, another reference to the 2003 prologue.

Remaking a foreign film according to Hollywood standards has, of course, much to do about technique and technology.


domain: sde sdu

text:
F Toublanc

I Brenon

T Coulombier

O Le Moine

Fortnightly tidal asymmetry inversion and its impact on salinity distribution and sediment net transport in a shallow macrotidal estuary (Charente, France)

Keywords: Estuary, Tidal asymmetry, Saline intrusion, Sediment dynamics, Numerical Modeling

Tidal asymmetry has a strong impact on estuarine hydrodynamics and sediment dynamics. Extensive research has been dedicated to studying tidal dynamics in semi-diurnal macrotidal estuaries, leading to the expression of several generic behaviors. Maximum current velocities and durations of the ebb and flood are often used to characterize the asymmetry encountered in the estuary.

The Charente estuary (French Atlantic coast) presents the particularity of being connected to a basin where the oceanic tide is already modified by the interactions with the continental shelf. The interaction between these externally generated overtides and the estuarine dynamics results in a spatially and fortnightly variable tidal asymmetry. The studied estuary is alternatively dominated by the ebb during neap tides and by the flood during spring tides, whereas most macrotidal estuaries subject to a semi-diurnal tidal regime are flood-dominant, without asymmetry inversions.

A two-dimensional hydrodynamics model is used to investigate the connection between spring-neap inversions of the tidal asymmetry and the harmonic composition of the tide. Resulting salinity distributions and barotropic tidal currents are compared for different configurations, and the possible impact on sediment dynamics is discussed. Results show that asymmetry inversions tend to create sediment accumulation and salinity concentration in an intermediate zone between the river mouth and Rochefort, approximately 20 km upstream.

Introduction

Investigating estuarine hydrodynamics is essential to understand these systems that are critical for sanitary and economic reasons. At the interface between land and ocean, estuaries are submitted to an important anthropic pressure. Many activites (fisheries, harbours, leisure, . . . ) are strongly dependent on the water quality and sediment related issues such as siltation. Although generic behaviors can be deducted from the numerous studies carried out on estuarine hydrodynamics, each system has its specificities. This work focuses on the tidal asymmetry observed in the Charente estuary (Fig. 1). The distortion of the tide in estuaries is commonly observed, and has been the object of many studies [START_REF] Aubrey | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part I : Observations[END_REF][START_REF] Bolle | The influence of changes in tidal asymmetry on residual sediment transport in the Western Scheldt[END_REF][START_REF] Fortunato | Influence of Intertidal Flats on Tidal Asymmetry[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF][START_REF] Prandle | Relationships between tidal dynamics and bathymetry in strongly convergent estuaries[END_REF]. Depending on several characteristics (bathymetry, geometry, tidal regime), estuaries can be ebb-dominant if the duration of falling tides exceeds that of rising tides, or flood-dominant in the opposite case. This asymmetry has a direct impact on the hydrodynamics, but also on the salinity and the sediment dynamics of the system. In estuaries where the mean water depth is larger than the tidal range, shorter rising (or falling) tides are associated with stronger flood (or ebb) currents. Current velocities have a direct impact on the bed shear stress which is one of the control parameter for erosion processes, with the nature and state of the sedimentary bed [START_REF] Mehta | Surface erosion of fine-grained sediment revisited[END_REF][START_REF] Tolhurst | A comparison and measurement standardisation of four in situ devices for determining the erosion shear stress of intertidal sediments[END_REF]. Consequently, ebb or flood dominance in terms of durations and velocities are often completed by a dominance in terms of net sediment transport [START_REF] Aubrey | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part I : Observations[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF][START_REF] Fry | Tidal Velocity Asymmetries and Bedload Transport in Shallow Embayment8[END_REF]. Ebb dominated estuaries will tend to export sediment, whereas flood-dominated estuaries will generate upstream sediment transport [START_REF] Allen | Effects of tides on mixing and suspended sediment transport in macrotidal estuaries[END_REF][START_REF] Dyer | Estuaries: a Physical Introduction[END_REF]. Tidal asymmetry is also a driving mechanism controlling the formation and dynamics of the turbidity maximum in macrotidal estuaries [START_REF] Allen | Effects of tides on mixing and suspended sediment transport in macrotidal estuaries[END_REF].

The nonlinear interaction between the tide and the estuary provokes the growth of harmonics and compound tides of the main astronomical tidal constituents. [START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF] studied the interaction between the M2 and M4 harmonic constituents of the tide to determine the direction of the asymmetry (flood or ebb dominated) and the degree of distortion of the tide. The shorter rising tides of flood dominance correspond to a relative sea surface phase (2ϕ M2 -ϕ M4 ) between 0˚and 180˚. For shorter falling tides and ebb dominance, the relative phase is between 180˚and 360˚. The magnitude of the tidal asymmetry caused by the estuary is indicated by the ratio of the two constituents amplitudes (a M4 /a M2 ).

This distortion is determined by two effects related to the estuary characteristics: frictional effects of the interaction between the tidal currents and the channel, and intertidal stor-age occurring in the presence of tidal flats or marshes [START_REF] Boon | On basin hypsometry and the morphodynamic response of coastal inlet systems[END_REF][START_REF] Speer | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part II : Theory[END_REF][START_REF] Speer | Nonlinear hydrodynamics of shallow tidal inlet/bay systems[END_REF]. To evaluate the impact of the frictional effects, the ratio of the M2 offshore amplitude and the channel depth at mean sea level (a/h) can be calculated. If a/h is greater than 0.3, the frictional influence is larger at low water than at high water, causing flood dominance. The water level propagation is slowed at low water, leading to shorter rising tides and greater flood velocities. If it is inferior to 0.2, the channels are deep compared to the degree of asymmetry and the estuary is expected to be ebb-dominant. The ebb duration is shorter and stronger ebb velocities are expected. For intermediate values of a/h, the system can be flood or ebb dominanted, depending on the intertidal storage.

The intertidal storage effect is evaluated by calculating the ratio of the volume of water stored between high and low water in intertidal areas divided by the channel volume of water at mean sea level (V s /V c ). When V s /V c is large in relation to a/h, the intertidal area is large enough to slow down the propagation of high water, causing longer flood durations and greater ebb velocities. A large reduction of the cross-sectional area of the channel at the entrance of a bay can provoke a long term asymmetry inversion from ebb to flood dominance [START_REF] Boon | On basin hypsometry and the morphodynamic response of coastal inlet systems[END_REF]. On the other hand, a weakly flood-dominant estuary could become ebb-dominant, due to the large import of sediment associated with strong flood currents, leading to an increase of the intertidal flats area [START_REF] Boon | On basin hypsometry and the morphodynamic response of coastal inlet systems[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF][START_REF] Speer | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part II : Theory[END_REF]. Along the border between Belgium and the Netherlands, deepening of the channels by dredging in the Scheldt estuary also caused a diminution of flood dominance, evolving towards ebb dominance [START_REF] Bolle | The influence of changes in tidal asymmetry on residual sediment transport in the Western Scheldt[END_REF]. In the case of Skagit River [START_REF] Nidzieko | Tidal asymmetry and velocity skew over tidal flats and shallow channels within a macrotidal river delta[END_REF] or the Murray Mouth coastal lagoon [START_REF] Jewell | Tidal asymmetry in a coastal lagoon subject to a mixed tidal regime[END_REF], under the influence of mixed diurnal/semi-diurnal tides, spring-neap asymmetry alternation have also been observed. These inversions are all consequences of significant long term changes in the estuary characteristics or a mixed tidal regime, which is not the case in the Charente estuary. The objective of this study is to understand the tidal dynamics encountered in the area that are leading to short term inversions of the tidal asymmetry. The impact on salinity distribution along the estuary and on barotropic tidal currents is investigated, and possible effects on sediment dynamics are discussed. In-situ measurements and the hydrodynamic model MARS-3D [START_REF] Lazure | An external-internal mode coupling for a 3D hydrodynamical model for applications at regional scale (MARS)[END_REF] are used for this purpose.

Study site

The French Atlantic Coast is under the influence of a semidiurnal tide. The Charente estuary (45˚96'N, 1˚00'W, Fig. 1), located to the south of La Rochelle (France) is small, shallow and characterized by the presence of large intertidal flats. The river flows into the Marennes-Oléron Bay, in the southern part of the pertuis Charentais. A dam is located at Saint-Savinien, 50 km from the river mouth. The river catchment is about 10 000 km 2 and total river length is 365 km. The bay's total surface is approximately 150 km 2 , 60% of it being occupied intertidal areas.

The Charente tidal regime is macrotidal, with mean and maximum tidal ranges respectively of 4.5 meters and 6.5 meters. Mean river discharge is of 70 m 3 /s, lowest values are under 10 m 3 /s and floods can reach 600-700 m 3 /s. Sediments in the estuary and in the oriental part of the Marennes-Oléron Bay are exclusively cohesive, with a very fine grain size [START_REF] Strady | Spatial and temporal variations in trace metal concentrations in surface sediments of the Marennes Oléron Bay. Relation to hydrodynamic forcing[END_REF]. In the western part of the bay, sediments are more sandy [START_REF] Tesson | Aspects dynamiques de la sedimentation dans la baie de Marennes-Oleron (France)[END_REF][START_REF] Bertin | Tidal inlet response to sediment infilling of the associated bay and possible implications of human activities: the Marennes-Oléron Bay and the Maumusson Inlet, France[END_REF].

The river is connected to the Marennes-Oléron bay, in which the tide is already distorted. Le Cann (1990) applied a modified version of the [START_REF] Battisti | A Simple Method for Estimating Barotropic Tidal Currents on Continental Margins with Specific Application to the M2 Tide off the Atlantic and Pacific Coasts of the United States[END_REF] theory to the Bay of Biscay shelf, and showed that the quarter-diurnal tidal constituents (M4, MS4 and MN4) are strongly amplified shoreward, because of resonance occurring on the shelf. This behaviour was verified numerically by [START_REF] Bertin | Importance of wave age and resonance in storm surges: The case Xynthia, Bay of Biscay[END_REF], who showed that the largest amplification by resonance occurred for MS4.

Salinity variations in the estuary represent a very important issue, since the Charente river is a source of fresh drinkable water for the area. When the river flow is very small, salinity could enter further in the estuary and affect the drinkable water intakes. Extensive oyster farming in the Marennes-Oléron Bay and leisure activities are also strongly dependent on the Charente water quality and water level. According to [START_REF] Ravail | Incidence du débit de la Charente sur la capacité biotique du bassin ostréicole de Marennes-Oléron[END_REF], in Summer, 90% of the freshwater input in the bay come from the Charente river. The pertuis Charentais present a particular geometry, with two islands (Ré and Oléron) and a sinuous coastline, which has a direct influence on the estuarine dynamics.

Material and methods

Numerical modeling

The numerical model MARS-3D (Model for Applications at Regional Scale) used for this study has been fully described by [START_REF] Lazure | An external-internal mode coupling for a 3D hydrodynamical model for applications at regional scale (MARS)[END_REF]. It is a finite differences model, resolving the shallow water (or Saint-Venant) equations when running in 2D mode.

The model MARS-3D was used to determine the behavior of the estuary in response to different hydrodynamic conditions. The effect of the harmonic composition of the tide at the boundaries was investigated more particularly.

In order to determine the impact of the tidal harmonic composition, a 2D configuration was developed. Only the tide, computed from the SHOM CST-France model (Le [START_REF] Roy | Réalisation et validation d'un modèle de marée en Manche et dans le Golfe de Gascogne. Application à la réalisation d'un nouveau programme de réduction des sondages bathymétriques[END_REF], and the daily river discharge were considered for the open boundary conditions. In order to determine very specifically the impact of the harmonic composition of the tide, no atmospheric forcing was considered for this configuration. Horizontal grid resolution was of 30m (1405 x 766 grid points). Bathymetric data (Fig. 2) was provided through several organizations (SHOM, Ifremer, EPTB Charente) with datasets from 2003, 2007 and 2010.

In-situ measurements

Fixed ADCP measurements (Sentinel-RDI, 1200 kHz, 5 minutes sampling frequency) were carried out in 2011 (from February 11th to April 8th) at the mouth of the estuary, close to Port-des-Barques (Fig. 1). Tide gauge recordings are available at Rochefort. Depth was corrected using a Demerliac filter, in order to compare data with the water levels obtained from the model without atmospheric forcing. Due to the ADCP emersion during low waters of spring tides, comparisons with velocities is not available.

Results

Analytical analysis

The amplitudes and phases of the principal tidal constituents at the mouth of the estuary are summarized in Table 1. Results were obtained from a 57 days harmonic analysis performed with the MAS software of the French Navy Hydrographic Office (SHOM), which allows calculations with small time series. According to [START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF], the relative phase 2ϕ M2 -ϕ M4 is of 187.28 and the amplitude ratio a M4 /a M2 of 0.09, suggesting that the Charente estuary would be ebbdominated (Table 1). Considering the geometric and tidal characteristics of the area, the two dimensional parameters a/h and V s /V c have also been calculated. At the mouth of the Charente River, a/h is evaluated at 0.23, with a M2 offshore amplitude of 1.75m and average channel depth of 7.6m. This value alone does not allow concluding on the direction of the asymmetry encountered. The intertidal storage ratio (V s /V c ) is estimated at 1, which is large in comparison to a/h. These results suggest again that the tidal response of the estuary should be ebb-dominant. However, based on in-situ measurements at the river mouth, it appears that in the Charente estuary, the tidal asymmetry dominance is determined by the spring-neap tidal cycle. The estuary is flooddominant during spring tides, and ebb-dominant during neap tides. These short term inversions are observed systematically and the level of distortion is modulated by the river flow and the tidal range.

Observations

Water levels and durations of ebb and flood were obtained from ADCP measurements at the mouth, and tide gauge record-ings at Rochefort (Fig. 3). Dashed lines mark the asymmetry inversions. Inversion from flood to ebb dominance occurs at the same time for both locations: approximately at the beginning of neap tides (February,25). Inversion from ebb to flood dominance occurs sooner during neap tides at Rochefort. The level of distorsion is also different between the two areas. Flood dominance is much stronger at Rochefort, with a difference in duration up to 5.7 hours, against 3.8 hours at the river mouth. By opposition, ebb dominance is stronger at the river mouth (duration difference up to 3.2 hours) than at Rochefort (2.3 hours).

Numerical Analysis

Free surface elevation and 2D currents are analyzed in this section. The evolution of the free surface has been studied for four different harmonic compositions of the tide at the system's open boundaries (Table 2).

Configuration A B C D Semi-diurnal constituents M2 M2,S2 M2,S2 M2,S2 Quarter- diurnal constituents - - M4 M4,MS4
In order to evaluate the impact of each component on the tidal asymmetry observed in the estuary, results obtained from numerical modeling are compared following several criteria: phase agreement, ebb/flood durations and maximum ebb/flood velocities. No comparison of the absolute water surface level is done since the objective is to study the distortion of the wave, and critical constituents are obviously missing to reproduce more precisely its variations.

Duration asymmetry

Water surface elevations at the mouth over a full neap/spring tidal cycle are obtained for each configuration (Fig. 4). Corresponding ebb and flood durations are presented. Asymmetry inversions are indicated with dashed vertical lines. Configurations A and B show almost no asymmetry inversion, with differences between ebb and flood durations respectively below 0.5 and 0.78 hours. Adding M4 to the harmonic composition at the mouth leads to an asymmetry inversion on the 27 th of February, which is exactly the day corresponding to the lowest tidal range. The maximum difference between ebb and flood durations is of 2.5 hours for spring tides and -2.25 hours for neap tides. A second inversion from ebb to flood dominance occurs on March, 4, as the tidal range is increasing. By taking into account MS4 in configuration D, both inversions occur sooner and the maximum (ebb-flood) duration reaches 2.5 hours during spring tides, against 2 hours during neap tides.

At the upstream station Rochefort (Fig. 1), the first noticeable difference is the response of the system to the basic configuration A (Fig. 5). When the tide was almost not distorted at the mouth, it is clear at Rochefort that a M2 incident tide provokes flood dominance (flood-ebb duration up to 2 hours). Configuration B returns the same type of results but with the modulation of the spring/neap tidal cycle, the level of distortion being stronger for high tidal ranges. Configurations C and D reproduce the asymmetry inversion observed at the mouth. However, ebb dominance is much weaker during neap tides: maximum duration difference is 4 hours during spring tides (flood dominance), against 1 hour during neap tides (ebb dominance). The ebb dominance phase is also shortened by more than two days, when comparing to the results at the mouth (Fig. 4).

Regarding the duration asymmetry, the mouth appears to be driven by an alternation between flood and ebb dominated periods, with comparable levels of distortion. On the other hand, the area of Rochefort is mostly dominated by the flood, with weaker and shorter ebb dominance during neap tides.

Velocity asymmetry

Tidal asymmetry in ebb and flood durations is often completed by an asymmetry in current velocities. Shorter rising tides and longer falling tides are then associated with stronger flood currents and weaker ebb currents, and vice versa in the opposite case. Fig. 6 and Fig. 7 present the same water level series as in Fig. 4 and Fig. 5, but completed by the ratio of the maximum flood velocity over the maximum ebb velocity. If the velocity ratio is over 1, flood currents are stronger than ebb currents, indicating flood dominance. Ebb dominance oc-curs for a velocity ratio below one. Dashed lines are indicating the moments of asymmetry inversions observed with ebb and flood durations in the previous section. At the river mouth, the velocity ratio is mostly following the same pattern as the duration asymmetry. Configuration A shows a constant slight flood dominance. Configuration B shows almost no asymmetry during spring tides, and flood dominance during neap tides. Asymmetry inversions are observed once the quarter-diurnal constituents are taken into account, in configurations C and D, and are almost in phase with duration asymmetry inversions. However, when duration asymmetries were almost equivalent between ebb and flood dominance, velocity asymmetry is a lot stronger for flood dominance than it is for ebb dominance.

At Rochefort, the velocity asymmetry is ebb-dominated for the simplest M2 tidal forcing, whereas duration asymmetry is flood-dominated (Fig. 3). The same opposition is noticeable for the M2S2 tidal forcing with stronger ebb dominance during neap tides. As in the previous paragraph, configurations C and D show velocity asymmetry inversions but with higher phase differences with the duration asymmetries. Moreover, ebb dominance during neap tides is stronger than flood dominance during spring tides, by opposition with the results at the river mouth.

Summary and comparison with measurements

The best agreement with data is observed with the last configuration (M2, S2, M4 and MS4 tidal forcing), even if differences remain for the exact moments of inversion.

Calculations on ebb/flood durations and flood/ebb maximum velocities are presented in Tables 3 and4, for the two locations.

At the mouth, duration asymmetry is of the same order of magnitude between ebb and flood dominance, with a good agreement with ADCP data. Both duration and velocity asymmetries are stronger for flood dominance.

The Rochefort area is characterized by an opposition between duration and velocity asymmetries. Duration asymmetries show stronger flood dominance than ebb dominance, which is confirmed by calculations made with tide gauge data. On the other hand, maximum velocity ratios show stronger ebb dominance. This is mostly explained by the presence of intertidal flats in the area, constraining the ebb flow for low water levels. Maximum flood velocity is reached between 1.5 and 2 hours after the beginning the flood, against 3.5 hours to 5 hours for the maximum ebb velocity. During spring tide, even if the flood duration is shorter, ebb currents are then equivalent or stronger than flood currents (Fig. 8, left), since the flow is limited to the channel when the water level reaches lower values. During neap tides (Fig. 8, right), tidal flats slow the flood tide when the water level reaches their height. Friction provokes then a decrease in flood velocities.

Discussion

Tidal asymmetry plays a very important role on estuarine dynamics. Extensive work has been done on determining the causes of flood or ebb dominance and its impact on sediment transport and hydrodynamics. In light of the particular situation encountered in the Charente estuary, the purpose of this study is to investigate the factors inducing tidal asymmetry inversion, to quantify the degree of distortion of the tide, and to evaluate its impact on the overall estuarine dynamics.

Origin and characteristics of the Charente tidal asymmetry

This study has shown the key role played by quarter-diurnal constituents in the tidal asymmetry inversion observed in the Charente estuary. The interaction between the M4 harmonic and the principal M2 constituent has already been proved [START_REF] Aubrey | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part I : Observations[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF]. How-ever, the introduction of the M4 harmonic in the model is necessary but not sufficient to reproduce the asymmetry observed in the estuary. By taking into account the MS4 harmonic, the inversions of asymmetry are reproduced in phase with observations. In the Charente estuary case, tidal asymmetry is resulting from the combination of the well-known distortion of the semi-diurnal tide in estuaries and the incidence of a tidal wave already composed of high amplitude harmonics, developed by the interaction with the continental shelf [START_REF] Le Cann | Barotropic tidal dynamics of the Bay of Biscay shelf[END_REF][START_REF] Bertin | Importance of wave age and resonance in storm surges: The case Xynthia, Bay of Biscay[END_REF].

The Charente estuary presents a time and spatial dependent tidal asymmetry: (1) at the mouth, asymmetry is mostly determined but the spring/neap variations, duration and velocity asymmetries concur (Fig. 4 and Fig. 6); (2) upstream, asymmetry is still subject to spring/neap modulations, but velocity asymmetry is mostly ebb dominated (Fig. 7) whereas duration asymmetry is mostly flood dominated (Fig. 5). The impact of tidal flats on this phenomenon has been demonstrated by several authors [START_REF] Speer | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part II : Theory[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF][START_REF] Fortunato | Influence of Intertidal Flats on Tidal Asymmetry[END_REF]. At the mouth, the estuary is wider, reducing the impact of mudflats on cross-section variations and current velocities, especially during spring tides. However, the Rochefort area, where tidal flats are highly present, is consistent with this phenomenon. Depth variations also need to be considered. At the river mouth, mean channel depth is around 7.5 meters. When moving upstream, [START_REF] Brown | Flood/ebb tidal asymmetry in a shallow sandy estuary and the impact on net sand transport[END_REF][START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF][START_REF] Moore | Morphological evolution of the Dee Estuary, Eastern Irish Sea, UK: A tidal asymmetry approach[END_REF][START_REF] Wang | Morphology and asymmetry of the vertical tide in the Westerschelde estuary[END_REF] deeper channels favor ebb dominance, against shallower waters for flood dominance. Combination of average depths and intertidal flats at the mouth would then favor asymmetry inversions in function of the tidal range. Depper upstream parts, also associated with intertidal flats would lead to ebb dominance most of the time, even if asymmetry inversions are observed.

Impact of tidal asymmetry inversions on salinity

Impact on spatial distribution

This section is focused on the impact of the different types of asymmetry described previously on the two-dimensional salinity distribution in and out of the estuary. Comparisons of salinity levels are made subtracting values from configuration D, which is the closest to reality, (M2, S2, M4 and MS4 tidal forcing) to values from configuration B (M2 and S2), in order to evaluate the differences between two cases with and without asymmetry inversion (Fig. 9).

Positive values indicate higher salinity levels for the M2S2 tidal forcing, against negative values, indicating higher salinity levels for configuration D (M2, S2, M4, and MS4). The strongest differences are observed at low water of spring tides, with a maximum difference above 12 psu.

At low water, both for spring and neap tides, salinity at the mouth and out of the estuary is stronger for the case without asymmetry inversion, at the exception of the channel sides. Upstream differences are negligible. At high water, the response of the system is different between spring and neap tides. The lowest tidal range induces higher salinity levels within the estuary for configuration D (up to 3.9 psu), whereas spring tides provoke lower salinity levels for this case (up to -3.6 psu).

Impact on saline intrusion

Contour comparisons are made during a spring-neap tidal cycle (Fig. 10), to evaluate the dynamics of the saline intrusion. Comparisons are made using the same configurations and calculations as in the previous section, with salinity levels extracted from the model at several points along the estuary.

Positive values of the distance are representative of points located upstream, negative values represent downstream points. The highest differences between the two configurations are observed during the transition from spring to neap tides (21 st to 25 th of February), especially at downstream low water (up to 16 psu) and upstream during the second part of the rising tide (up to -10.5 psu).

During neap tides, salinity is higher for configuration D for the most part of ebb and flood tide. This suggests that salinity is more concentrated by tidal oscillations when there are asymmetry inversions occurring during the cycle. On the other hand, salinity intrusion appears to be higher without asymmetry inversion.

Net sediment transport asymmetry

Brown and Davies (2010) proposed two ratios to determine the ebb or flood dominance of sediment transport over a crosssection: (1) the ratio of peak flood velocity over peak ebb velocity u p , (2) the ratio of flood and ebb durations during which the velocity is over a threshold for sediment movement T d . Ebb dominance is obtained for values of u p inferior to 1 and values of T d superior to 1. But they also show that it can be obtained for u p < 1.2 and T d < 1, representing a flood dominant duration asymmetry with ebb-dominant velocity asymmetry. Charente sediments are very fine, exclusively mud sediment, with a mean median grain size of 9 µm close to the mouth [START_REF] Strady | Spatial and temporal variations in trace metal concentrations in surface sediments of the Marennes Oléron Bay. Relation to hydrodynamic forcing[END_REF]. Moreover, as observed in Fig. 8, periods of slack water with very low velocities are short. In this paper, the velocity threshold is then considered to be exceeded for all ebb and flood durations, since very fine sediments in fluid mud can be easily resuspended in the water column by entrainment [START_REF] Mehta | Review notes on cohesive sediment erosion[END_REF]. Calculations are made over a full spring/neap tidal cycle to represent all possibilities equally, and u p is plotted against T d (Fig. 11).

Zone 1 is representative of the typical flood asymmetry with short and fast rising tides. Zone 2 is populated by points with longer rising tides but with higher flood velocities. Typical ebb dominant asymmetry corresponds to zone 3, and zone 4 is characterized by longer falling tides but with higher ebb velocities. Following [START_REF] Brown | Flood/ebb tidal asymmetry in a shallow sandy estuary and the impact on net sand transport[END_REF] criteria, points located in zone 1 below the solid line (u p < 1.2 and T d < 1) and in zones 3 and 4 (u p < 1 and T d < 1) are representative of ebb-dominant sediment transport. At Rochefort, sediment transport is then ebb-dominated for 90% of the cases, against 65% for the river mouth.

Comparisons of salinity levels show that asymmetry inversions tend to reduce saline intrusion. However, higher salinity levels are observed in the central part of the saline mass, suggesting that asymmetry inversions induce a "concentration" of salinity with tidal oscillations. These salinity dynamics can also be related to sediment dynamics exposed in Fig. 11. In terms of net sediment transport, the Rochefort area appears to be ebbdominated most of the time, inducing net sediment export. On the other hand, the river mouth is more equally divided between periods of ebb and flood dominance. Flood dominance and net import at the mouth, associated with ebb dominance and net export at Rochefort suggest that the intermediate zone between those two locations is prone to sediment accumulation. According to Fig. 6 and7, this configuration occurs mostly during the transition from spring to neap tides. The highest salinity differences are also observed during this transitional period (Fig. 10), suggesting again that salinity and sediment dynamics are closely related and impacted by asymmetry inversions.

These modeling results are consistent with sediment accretion measured on the mudflats in the estuary, since small variations are observed near the mouth (8 cm a month) whereas upstream measurements show accretion up to 40 cm a month during summer [START_REF] Coulombier | Seasonal monitoring of sediments dynamics in a highly turbid estuary (Charente Estuary, France): source and sink of the turbidity maximum[END_REF]. Sediment fluxes calculated with hydrodynamic modeling and turbidity measurements also suggest alternations between net import and net export at the river mouth, mostly determined by the spring-neap variations of the tide [START_REF] Toublanc | Salinity and suspended sediment dynamics in response to forcing changes in a small macrotidal estuary[END_REF]. Ebb dominance in the upstream part will most likely be enhanced by the accumulation of fluid mud in the upstream part and the associated decrease in friction, which is contributing to flood dominance.

A switch from flood to ebb dominance because of sedimentary infilling and flat formation and/or extension has been discussed by many authors [START_REF] Speer | A Study of Non-linear Tidal Propagation in Shallow Inlet / Estuarine Systems Part II : Theory[END_REF][START_REF] Fortunato | Influence of Intertidal Flats on Tidal Asymmetry[END_REF][START_REF] Moore | Morphological evolution of the Dee Estuary, Eastern Irish Sea, UK: A tidal asymmetry approach[END_REF]. In the Charente estuary case, we can wonder if the accumulation of sediment observed and suggested by this study could lead to a change in tidal propagation and therefore in net sediment transport. The relative equilibrium reached at the river mouth suggest that the possible morphological changes induced by tidal asymmetry in sediment transport are not strong enough to change the system dynamics. However, human intervention by regular dredging of this area tends to counteract the accumulation of sediment in the channel.

As demonstrated by [START_REF] Allen | Effects of tides on mixing and suspended sediment transport in macrotidal estuaries[END_REF], tidal asymmetry is a driving mechanism leading to the formation of a turbidity maximum in macrotidal estuaries. Since tidal asymmetry is strongly dependent on the spring/neap tidal cycle in the Charente estuary, turbidity maximum dynamics should also be partly determined by this cycle. Previous work already proved that neap tides favor sedimentation and depletion of the turbidity maximum, wheras spring tides favor resuspension and turbidity maximum extension [START_REF] Allen | Effects of tides on mixing and suspended sediment transport in macrotidal estuaries[END_REF][START_REF] Dyer | Estuaries: a Physical Introduction[END_REF]. In addition to these dynamics, related to the strength of current velocities, fornitghtly asymmetry inversions could also play a key role for the turbidity maximum. Transition from spring to neap tides is characterized by ebb-dominant current velocities at Rochefort against flood-dominant velocities at the river mouth (Fig. 6 and Fig. 7), which could lead to turbidity maximum concentration and trapping in an intermediate zone where current velocities would neither ebb or flood-dominated. Inversely, transition from neap to spring tides would favor extension and downstream movement of the turbidity maximum because of ebb dominance at both locations.

Conclusion

In the case of a time and spatial dependent asymmetry, as observed in the Charente estuary, parameters such as V s /V c and a/h [START_REF] Friedrichs | Non-linear Tidal Distortion in Shallow Estuaries : a Synthesis[END_REF] cannot give a full representation of the tidal asymmetry. Moreover, by considering only the relative importance in phase and amplitude of M2 and M4, the strong impact of the MS4 harmonic, demonstrated in this paper, is left out. Finally, we showed that asymmetries in durations, velocities and net transport are not always related.

Asymmetry inversions provoke changes is salinity distribution, mostly resulting in weaker salinity intrusion and stronger salinity levels in the central part of the saline mass. Net sediment tranport calculations suggest that an accumulation occurs between the river mouth and Rochefort, which is confirmed by observations. Further investigation is needed to determine the possible impact of this behavior on the long-term morphological evolution of the Charente estuary.

Better understanding of the impact of asymmetry inversion on sediment dynamics could be achieved by applying the different configurations developed in this study to a nested 3D hydrosedimentary model. Net sediment transport calculations at different locations and turbidity maximum modeling would allow confirmation of the tendencies pointed out in this paper. The effect on mixing and stratification could also be investigated.

Figure 1 :

 1 Figure 1: Charente river, from the Saint-Savinien dam to the mouth. Framed: modeled area.

Figure 2 :

 2 Figure 2: Bathymetric data used for numerical modeling

Figure 3 :

 3 Figure 3: Surface elevation (left), ebb and flood durations (right) at the river mouth (up) and Rochefort (down).

Figure 4 :

 4 Figure 4: River mouth: water surface elevation (left), ebb and flood durations (right) for each harmonic composition of the tide at the model boundary.

Figure 5 :

 5 Figure 5: Rochefort: water surface elevation (left), ebb and flood durations (right) for each harmonic composition of the tide at the model boundary.

Figure 6 :

 6 Figure 6: River mouth: water surface elevation (left), velocity ratio Vmax f lood /Vmax ebb (right).

Figure 7 :

 7 Figure 7: Rochefort: water surface elevation (left), velocity ratio Vmax f lood /Vmax ebb (right).

Figure 8 :

 8 Figure 8: Current velocity and water surface elevation at Rochefort for spring (left) and neap tides (right).

Figure 9 :

 9 Figure 9: Salinity distribution differences between configurations B and D

Figure 10 :

 10 Figure 10: Top: water level at the mouth, configuration D. Bottom: salinity differences in function of the distance from the mouth and time, configuration B-D

Table 1 :

 1 Amplitudes and phases of the main tidal harmonic constituents (Charente river mouth)

	Harmonic	Amplitude (cm) Phase (deg)
	constituents
	M2	174.34	112.43
	S2	60.96	144.29
	N2	38.17	87.88
	M4	15.75	37.58
	MS4	9.05	161.01

Table 2 :

 2 Amplitudes and phases of the main tidal harmonic constituents (Charente river mouth.)

Table 3 :

 3 Dimensionless parameters used to characterize the tidal asymmetry at the river mouth in function of the model configuration

	Location			River mouth
	Configuration Harmonics	A M2 M2,S2 M2,S2,M4 M2,S2,M4,MS4 B C D	ADCP data
	Minimum ebb/flood dura-	1	0.89	0.7	0.72	0.6
	tion
	Maximum ebb/flood dura-	1.08	1.14	1.5	1.5	1.88
	tion
	Minimum flood/ebb max ve-	1.1	1.05	0.83	0.92	-
	locity ratio
	Maximum flodd/ebb max	1.21	1.41	1.44	1.3	-
	velocity ratio

Table 4 :

 4 Dimensionless parameters used to characterize the tidal asymmetry at Rochefort in function of the model configuration

	Location

Acknowledgements

The authors gratefully acknowledge funding from the Conseil Général of Charente Maritime, the CNRS, the FEDER and the University of La Rochelle. The REFMAR portal is also acknowledged for the tide gauge data provided, as well as Ifremer for the bathymetry and the MARS3D code. The authors thank particularly Florence Cornette, Philippe Geairon, Olivier Le Moine, Stéphane Robert and Jean-Luc Seugnet for their precious help on the ADCP campaign.