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Sandy Fluvial Systems Assignment

Introduction

1The Lagoon of Venice is located on the eastern side of the Po plain in the Northern Adriatic Sea. It is about 55 km long and 13 km wide. The lagoon constitutes a remnant of the old lagoonal belt that used to rim the northern Adriatic coast until the conclusion of the land reclamation projects that started in Middle Ages and ended up in the period from the end of the 19th c. to the second half of the 20thc. The Lagoon of Venice and its mainland were involved in a complex geomorphological transformation triggered by repeated fluvial diversions carried out by the Republic of Venice mainly during 16th and 17th c. in order to turn the main fluvial outlets outside the Lagoon of Venice. Fluvial deposition was responsible of a progressive sedimentary infilling, causing water surfaces reduction and canals deactivation. Tidal inlets were narrowing and shallowing due to littoral transport of fluvial sands from the deltas belonging to the main rivers debouching into the sea just close to the lagoon (Adige, Brenta and Bacchiglione rivers, to the South; Piave River to the North; Favero, 1983). The consequence was an incipient status of crisis in the economic and environmental system, so that the “Serenissima” (as the Republic of Venice used to call itself) started a huge programme of artificial river diversions that lasted almost two centuries and brought to a change in the paths of Po, Brenta, Bacchiglione, Marzenego, Sile, Piave, Livenza and minor rivers.

2These actions were performed together with a complex of ordinary management of the natural environment that led to an artificialisation of the lagoon. At the end of the transformations, not only the hydraulic network radically changed, but also the sedimentary dynamics and the geomorphological setting of the whole alluvial plain, lagoon and coastal stretch. The present geomorphological framework is the legacy of the decision taken by the Venetian engineers in river management. Today, even the great dams and gates system at the lagoon inlets (the so-called “Mo.S.E.”; cf. Ghezzo, 2010) are facing the inverse problem of “high water” events, erosion of land and submersion of Venice that were enhanced by the negative sedimentary budget induced by river diversions and subsidence. Today, thousands of maps, used from the 16th c. for planning fluvial diversions and land reclamations, are collected at the Archivio di Stato di Venezia (National Archive of Venice) and were employed to reconstruct the ancient landscape of the Republic of Venice.

3The cartographic analysis was performed producing synthetic maps that give precious information on the diversion project, their effectiveness, the geomorphological changes both related to human intervention and recent environmental changes. The artificial diversions in the alluvial plain surrounding the Lagoon of Venice have been a topic of interest from different points of view. They have been studied since the 18th c. by famous hydraulic engineers and geographers (Zendrini, 1811; Marcon, 1878; Marinelli, 1881; Averone, 1911) that realised extended and complete works depicting the changes in alluvial pattern. More recent authors dealt with the hydraulic network in ancient time, both from an archaeological point of view (Bosio, 1967; Rosada, 1979; Bosio, 1994), and from a human geography perspective (Cisotto, 1968; Tiepolo and Marozzo Della Rocca, 1972; Favero et Serandrei Barbero, 1980; Cavazzana Romanelli and Casti Moreschi, 1983; Favero, 1983; Bevilacqua, 1984; Tiepolo, 1984; Bevilacqua, 1992; Tiepolo, 1992; Caniato, 1995, 1997; Vallerani, 2008). These latter deal mainly with the diachronic reconstruction of the landscape through the analysis of historical maps. In the thirties of the 19th c., the main monographs belonging to the most famous hydraulic engineers of the Republic of Venice, Alvise Cornaro and Niccolò Sabbadino, were published. Cornaro’s projects were addressed towards an extensive land reclamation, thus largely reducing the lagoon extension, while, on the contrary, Sabbadino aimed to the maintenance of the tidal fluxes and to the water dynamics. Many are the works containing or dealing with the maps they prepared in order to illustrate their projects (Cessi, 1930, 1931, 1936, 1941, 1943 a to c; Cessi and Spada, 1952). More recent papers give a geomorphological and historical reconstruction of the lagoon and its fringe, making use of historical maps and archive documents (Dorigo, 1983; Favero et al., 1988; Dorigo, 1994; D’Alpaos, 2010). In its monograph on northern Adriatic coasts, M. Zunica (1971) examined many Venetian historical maps and reconstructed the coastline evolution and the fluvial diversion during the last centuries. The historical map database, published by IUAV University of Venice and availabe on line, has led to the publication of extended catalogs of complete series of maps archived at the Correr Museum, the National Archives of Venice, the Querini Stampalia and the Marciana Library (Scarso, 2002; Baso et al., 2003; Cantile, 2004; Valerio, 2007). Much more recent is the publication of the anastatic copy with explanatory notes of the great Austro-Hungarian military map prepared by Anton Von Zach in 1797-1805 and edited by M. Rossi (2005), which is a notable example of methodological approach to this matter

4The present paper considers the geomorphological background of the studied areas. A remarkable number of papers relating the Venetian Plain have been recently published, though this research was mainly based on P. Giandon et al. (2001), A. Bondesan et al. (2004 a and b, 2008 a and b), and P. Furlanetto (in press); the first extended geomorphological map of the Po and Venetian-Friulian Plain was published by MURST (1997) with explanatory notes in G.B. Castiglioni (1999) and G.B. Castiglioni and G.B. Pellegrini (2001).

Materials and methods

5The ancient hydrographical and geomorphological framework was reconstructed for the whole area (more than 2500 km2) by use of historical maps, georeferenced and overlaid to available geomorphological maps and aerial photographs, as part of the Imago Project (Image Map Archive Gis Oriented). The Imago Project is mainly devoted to the implementation of a database concerning the historical maps of the Lagoon of Venice and its fringe (Furlanetto and Primon, 2004; Furlanetto et al., 2004, 2009). The final aim is the diachronic reconstruction of the hydrographical and geomorphological changes in the Lagoon of Venice and its hinterland during the 16thand the 17th c. The project started in 2001 and is still in course; it is funded by Magistrato alle Acque-Consorzio Venezia Nuova – Informative Service of Venice, through a protocol with the National Archives of Venice. This latter collects a huge amount of historical maps, more than 12,000, that were issued as documents for the decree of acts by the Republic of Venice from the 15th to the 18th c., to exert a strict control over the territory.

6The use of ancient cartography is a quite common mean to investigate the past, but it is usually limited to one or few maps, without a systematic analysis and often without georeferentiation, even though some authors made a valuable use of historical maps (Surian et al., 2008,2009; Cremonini and Samonati, 2009; Podobnikar, 2009; Szekely, 2009; Bruna et al., 2010; Petrovszki and Meszaros, 2010). The content of the maps is not usually validated and a multidisciplinary approach is often missing. Moreover, the researchers are interested in specific topics such as fluvial change (e.g., Timar et al., 2005 a and b; Kovacs, 2010; Petrovszki and Timar, 2010; Zamolyi et al., 2010) or coastal fluctuation (e.g., Hopley et al., 2007; Jabaloy-Sanchez et al., 2010) and not to the whole environmental system. We made an extensive use of Geographycal Information Systems, adapting all the studied maps to the same system of coordinates and thus allowing to integrate different available geodatabases, above all the Geomorphological Map of the Province of Venice (1:20,000; Bondesan et al., 2004 a and b), the Map of the Geological Units (1:20,000; Bondesan et al., 2008b), the Soil Map (1:50,000; Giandon et al., 2001) and the Map of the Archaeological Landscape (1:50,000; Furlanetto, in press). A comparison was performed through the overlay map analysis with 17th-21th c. topographical maps; the most effective are: the Topographisch-geometrische Kriegs karte von dem Herzogthums Venedig made by Anton Von Zach in 1797-1805 (Rossi, 2005), the topographic survey of Auguste Dénaix (1809-1811), the map of Antonio de Bernardi made in 1843, the Topographic Map of the Lombardo Veneto Reigndrawn by the Austrian Imperial Royal General Staff made in 1833, and the historical series of 1:25,000 scale National Topographic Map printed by the Geographical Military Institut since 1861. We also made large use of aerial photographs, mainly 1:17,000 to 1:33,000 scale, taken since 1943 and available at the Cartographical Office of the Regione Veneto. About 7200 maps belonging mainly to the Archivio Storico Nazionale (National Archives) of Venice were observed and controlled, selecting 356 among them according to the author, the century, the area represented, the commissioner and its intrinsic characteristics. The most representatives were georeferenced and the major landforms and geographical information were redrawn; through these analyses four maps 1:50,000 were created, depicting the ancient morphology and hydrographic network at 1550, 1600, 1650 and 1700. A comparison was performed also for the pre-geodetic available maps of 18th, 19th, and 20th c.

7Each record is linked to a raster image of the map and is organised in 12 forms, filled with all the information related to the single map. The filling mask is organised according the archive and technical data, as allocation, dimension, material etc.; the geographical and descriptive data refer to the coordinates of vertexes, the toponyms and hydronyms and the geomorphology; then, the chronology and the historical-cartographical analysis consider the historic framework; bibliography, with hypertext links to scanned original papers, and secondary data complete the mask, for a total of 101 different descriptive fields. The form is quite innovative, following the government criteria for cataloguing according to the Documentation Centre for the Archive Documents Catalogue and adopting an interpretative section where each map is deeply analysed and compared with the present topography and geomorphology. One of the main problem in cartographical analysis is that the chronology of the map is very often mistaken due to wrong archive information or because it was originally a copy itself of former maps. For this reason, each map has been strictly verified through the comparison with the topographical elements represented. A deeper analysis of each map led to a objective assessment about its reliability, the quality and the quantity of geographical information. The appreciation has been defined giving a score to consistency as: (i) author; (ii) hydrography; (iii) land use; (iv) cartographic symbols; (v) details abundance; (vi) geometry; (vii) originality.

8All the maps were divided into two categories according to the informative quality. The I Level group is characterised by low deformation, abundance of control points for georeferentiation, large territorial coverage, reliability and precision of the map, trustworthy chronology, author capability. The available maps belonging to the I Level are 45, 22 related to the 16thc. and 23 to the 17th c. (tab. 1). All the I Level maps have been georeferenced and redrawn by use of a Geographycal Information System selecting 27 layers. The elements drawn are: water courses, both in lagoon and in the mainland, fluvial ridges, lakes, lagoons, beach ridges, roads, islands, fisheries, lagoonal canals, salt marshes, tidal flats, reeds, swamps, woods, grazings, embankments, coastal defenses and the coastline. Toponyms and hydronyms complete the map. The first maps belonging to 15th and 16th c. were not drawn according to a geographical projection, but just using visible ground control points. The astrolabe made use of fixed points as towers and churches, from which a windrose was traced, giving directions and distances of single represented elements. We georeferenced the historic maps on the base of the Technical Regional Map 1:5000 scale, being the main problem to find a sufficient number of common control points. The rivers courses are the main elements considered for georeferencing; since many canals and rivers has changed in time, the traces of palaeochannels inferred from photointerpretation were very useful to find more control points. More difficult has been the interpretation of the maps depicting the Lagoon of Venice, because they are deformed or lacking detailed information. The control points were used to build a polynomial transformation that converted the raster dataset from its existing location to the spatially correct location. Ground control points were possibly spread out over the entire raster dataset to get the best alignment results. The raster dataset was warped to permanently match the map coordinates of the target data using mainly a first-order polynomial transformation. When more links were available, second- or third-order transformations were performed. The root mean square error (RMS) was generally under 200 m, highly depending on the scale of the map. Resampling the raster dataset was made by nearest neighbor assignment. A second DB, the “Forma DB”, was created to systematically describe the major geomorphological elements refigured in historical maps. The forms are organised to describe the characteristics of single morphological forms as they are depicted in old maps and in comparison with present topography and the geomorphology. The evolutionary aspects have been faced comparing the whole set of maps collected into the Imago DB representing the same object and summarising the geological-geomorphological history of the single element. Natural and anthropogenic evolution are considered, focusing on the causes that induced morphological changes. When the morphological change is due to human activity (fluvial diversion, embankment, canal excavation, etc.), the actions taken are exhaustively described, also by use of scientific literature available. When possible, there is also a morphometrical analysis (height, length, depth, radius, etc.). The quality of the cartographical representation in a geomorphological perspective is given by the distinction between the geometric or the symbolic one. The persistence of the representation of a single element in maps having different date give the time of existence of the element itself.

Tab. 1 – List of historical maps classified in Level I from the IMAGO Data Base and partially in Level II
Tab. 1 – Liste des cartes historiques de Niveau I du Data Base Imago et en partie de Niveau II

Nr Imago

Author

Title

Archival date

Real date

Archival allocation

Level I

7

Filippini Giovanni, perito ing. ai Lidi, Lucchese Matteo, perito ing. della Laguna, Foin Stefano, vice perito

Veneziano territorio.

Zona con parte del taglio del Sile, della Fossetta con rete di altri canali; da Portegrandi verso est nord-est, alla Fossa Vecchia.

1750, 31 July

ASVE, Savi e esec., dis., Sile, 17

9

Dal Cortivo Angelo, dis. Pertic.re

Piave (fiume).

Corso del Piave da S. Donà, per Iesolo-Cava Zuccarina al mare presso il Cavallino. Vi sono altri fiumi tra i quali il Livenza da S.Lorenzo al mare.

1532

1532

ASVE, Savi e esec., dis., Piave, 2

11

De Castaldi Giacomo, piemontese

Piave (fiume).

Valle posta fra il Piave e il canale Largon, dal taglio del Re al mare, con canali minori e laghetti nella zona.

1562

1562

ASVE, Savi e esec., dis., Piave, 6

16

Anonymous

Piave ed altri fiumi.

Regolazione del Piave, Livenza, Sile, Zero e altri fiumi minori del territorio, confluenti nel mare.

1639, 30 August

1639

ASVE, Savi e esec., dis., Piave, 15/a

17

Bonotti Sebastiano, vice proto all'acque

Piave (fiume).

Il Piave dal Ponte di Piave al suo sbocco in mare, con vasta zona di terre arative, pascolive, boschive, a vigneti e valli prative e paludose ed estesa fascia litoranea da S.Erasmo al Porto di Caorle.

1641, 13 July

1641

ASVE, Savi e esec., dis., Piave, 16

23

Alberti Francesco, perito della laguna

Piave (area del).

Settore del litorale con entroterra da Venezia a Caorle e piano di regolazione dei fiumi in esso scorrenti.

1684, 21 September

1684

ASVE, Savi e esec., dis., Piave, 26

28

Boschetti Lorenzo, ing. per. Magistrato delle Acque

Piave (fiume).

Comprensorio dell' alveo vecchio e il taglio del Piave alla Livenza, da S.Donà e S.Giorgio al mare dal Porto di Piave al Porto di Caorle.

1724, 7 December

1684

ASVE, Savi e esec., dis., Piave, 39

38

Fissaro Andrea, detto sotto proto

Trevisano (territorio).

Comprensorio tra il Piave Vecchio e il Livenza da Gorgo Monticano al mare.

Anonymous

1563-1567

ASVE, Savi e esec., dis., Piave, 102

40

Cristoforo Sabbadino

Piave (fiume).

Settore del fiume da Nervesa al mare, per Jesolo e territorio trevisano alla sua destra, fino a Treviso e al Sile, con tratto di Laguna e il canale di Lio Maggiore.

Anonymous

1550

ASVE, Savi e esec., dis., Piave, 110

43

Dal Cortivo Nicolò, perteg.re disegnatore

Dragojesolo (valle di).

Comprensorio tra il Piave, la Cava del Caligo e il canale Piochioso.

1539

1539

ASVE, Savi e esec., dis., Piave, 127

46

Minorelli Angelo, pubblico perito

Jesolo (comprensorio di).

Jesolo, Equilio, Cava Zuccherina (pertinenze di). Comprensorio dei canali Amaniolo e Passarella al mare, con il Taglio Nuovo del Piave.

1724, 20 March

1675

ASVE, Savi e esec., dis., Piave, 130/a

49

Marcolin Jeronimo

Trevisano territorio: mappa territorio della provincia di Treviso.

Campanatico con nominativo dei proprietari tra i fiumi (da sud-ovest a sud-est in senso orario) Sile, Valio, Meolo, Fossa Vecchia e Nuova, Lanzon e Siletto.

1547, 15 February

1547

ASVE, Savi e esec., dis., Diversi, 3

53

Anonymous

Veneziano trevisano territorio: territori veneziano e trevisano.

Regolazione del Piave e dei fiumi Livenza, Sile, Zero, Dese, nell'ambito da Ponte di Piave a Torre di mosto, Caorle, Tre Porti, Burano, Mestre.

1639, 30 August

1639

ASVE, Savi e esec., dis., Diversi, 20

55

Francesco Fiorini

Territorio trevisano: territorio trevisano e parte del territorio veneziano.

Mappa dei fiumi Sile, Dese, Marzenego da Lancenigo, Treviso, Mestre all'alveo del vecchio Piave, Porto di Jesolo, Tre Porti, Mazzorbo.

1668, 15 July

prior 1664

ASVE, Savi e esec., dis., Diversi, 27 A

70

Anonymous

Laguna di Ve.

Settore centrale laguna di Venezia, con bordo lagunare, ponte del Brenta e Fusina, isole del Lido, Vignole, S.Erasmo.

Anonymous

1547?

ASVE, Savi e esec., dis., Diversi, 128/3

71

Anonymous

Veneziano territorio.

Territorio Padova o veneziano, compreso tra l'ultima parte del corso del Brenta, da Corte al Mare, il canale di Siocho e il litorale.

Anonymous

1542?

ASVE, Savi e esec., dis., Diversi, 128/4

79

Fontanella Bartolomeo, pertegador della comunità di Padova

Sette Saleri (valle del).

Parte della laguna con le isole di Torcello, S. Andrea, S. Angelo e S. Lorenzo.

1572, 25 October

1572

ASVE, Savi e esec., dis., Laguna, 2

80

Dal Cortivo Nicolò, disegnatore

Laguna di Venezia.

Laguna di Venezia a Chioggia con i litorali di Malamocco e Pellestrina , l'entroterra fino a Piove e Palvello, tra Marghera S.Giuliano e l'Adige.

1534, 8 March

1534

ASVE, Savi e esec., dis., Laguna, 3

81

Giovanni Trevisan, Nicolò e Giacomo Alberti

Zona barenosa-valliva di Fogolana e laguna sud-occidentale, tra il canale di Corte e Siocho, il Brenta Nuovo e il Bachiglione, il litorale dal porto di Chioggia a quello di Malamocco.

1542, 9 September

1542

ASVE, Savi e esec., dis., Laguna, 6

88

Cristoforo Sabbadino

Torcello.

Parte dell' isola di Torcello con Sant'Angelo, S. Cristina, S. Andrea, l'isola di S. Lorenzo, S. Felice ed una vasta zona della laguna.

1573, 25 September

1546-1573?

ASVE, Savi e esec., dis., Laguna, 21

89

Guglielmo Di Gradi

Laguna terre, prati e pascoli al limite della laguna di proprietà di Francesco Foscolo.

1580, 18 August

1580

ASVE, Savi e esec., dis., Laguna, 24

92

Bagatella Giovanni Battista

Caorle.

Mappa del territorio di Caorle con il litorale adriatico, il territorio retrostante e il corso del fiume Livenza ed il Lemene.

1596, 9 December

1596

ASVE, Savi e esec., dis., Laguna, 33

94

Anonymous

Venezia (laguna di).

Conterminazione della laguna da Chioggia a Malamocco al Taglio del Brenta.

1610, 18 December

1610-1657(?)

ASVE, Savi e esec., dis., Laguna, 39 II

95

Scola Alvise, per; Alberti Francesco, per.; Fabris Girolamo, per.

Caorle (fascia litoranea).

Fascia litoranea della Livenza al Tagliamento tra i termini del territorio di Caorle al mare.

1644, 3 January; 1645

1644

ASVE, Savi e esec., dis., Laguna, 44

100

Mozzi Scolari Stefano

Venezia (laguna di) dal porto di Chioggia al porto di Venezia dal Taglio Nuovissimo del fiume Brenta a Mestre, canal dell'Oselino.

1677, 8 July

1677

ASVE, Savi e esec., dis., Laguna, 53

104

Margutti Domenico

Venezia, conterminazione della laguna.

Mappa della laguna compresa tra il canal di Volpago e il canal di Tessera, da Malamocco a S. Erasmo.

1691, 20 March

1691

ASVE, Savi e esec., dis., Laguna, 64

106

Margutti Domenico per.alla laguna; Gornizai Angelo, proto alle f.

Laguna di Venezia.

Parte della laguna a sud-est della città col settore litoraneo del porto del Lido e quello di Malamocco

1690, June

1690

ASVE, Savi e esec., dis., Laguna, 71

107

Cornello Andrea, proto

Laguna di Venezia.

Conterminazione della laguna, compreso il lido fino al mare.

1706, 12 September

ASVE, Savi e esec., dis., Laguna, 74

109

Scalfuroto Tommaso

Laguna di Venezia.

Conterminazione della laguna dalla foce del Piave a Tre Porti e dal Taglio del Sile al Canal dell' Osellino.

1711, 24 August

ASVE, Savi e esec., dis., Laguna, 76/b

122

Anonymous

Chioggia.

Laguna valli e terraferma a sud di Chioggia, con lo (sbocco in laguna) in canali e fiumi.

Anonymous

1534-1540

ASVE, Savi e esec., dis., Laguna, 129

124

Anonymous

Laguna.

Mappa della Laguna del Lido di S. Erasmo al Cavallino e con parte del fiume Piave.

Anonymous

ASVE, Savi e esec., dis., Laguna, 145

127

Anonymous

Veneto (territorio).

Comprensorio del territorio con la laguna ed il litorale dal porto di Brondolo a quello di Cortellazzo, delineato dal Bacchiglione e Brenta fino a Bassano e dal Piave.

Anonymous

1650 (first half XVII Century)

ASVE, Savi e esec., dis., Laguna, 165 bis

145

Panatta Iseppo, per. ing. ord.; Orefesi Alvise per. straord.

Trevigiano comprensorio tra il fiume Meolo e il Musestre e Sile, con le località di Breda, Caniè, S. Biagio, Rovarè, Vallio, Meolo, S. Martino, Spercenigo, Biancade, Roncade e Musestre.

1612, 4 July

1612

ASVE, Beni inculti TV-Friuli, dis., 481/58/2a-2b

146

Perona Feliciano per. ord.; Vecellio Pietro per. straord.

Trevigiano (territorio).

Trevigiano comprensorio Meolo-Fossalta tra il fiume Meolo, la Fossa Vecchia e l'argine grande del Piave.

1598, 28 April

1598

ASVE, Beni inculti TV-Friuli, dis., 481/58/3

161

Gallo Gerolamo, Sotto Proto all Acque

Jesolo (territorio).

Comprensorio di Iesolo col litorale "Pineda", i centri di Cittanova e S.Donà, dal Piave alla foce della Livenza ai Canali Revedoli e Dosa.

1582, 8 September

1582

ASVE, Savi e esec., dis., Lidi, 14 bis

166

Anonymous

Litorale della Livenza (col suo percorso dalla Motta al mare) fino al Tagliamento, con altri fiumi intermedi.

1527

1527 (revisions at 1534)

ASVE, Savi e esec., dis., Livenza, 1

171

Fiorini Francesco, vice proto al M.; Bagatella Battista

S. Stino (Gastaldia).

Comprensorio della Gastaldia predetta tra i fiumi Livenza e Largone e Lemene.

1662, 6 July

1537

ASVE, Savi e esec., dis., Livenza, 7

176

Rossi Paolo, per.to a Mag.to B.I.; Minorelli Angelo e Cornello Andrea, per.to Mag. Acq.

Caorle (territorio).

Comprensorio paludi e valli della Livenza al Tagliamento e da Villa Viera al mare.

1691, 21 August

1691

ASVE, Savi e esec., dis., Livenza, 12

178

Anonymous

Settore del fiume da S. Stino alla sua foce nel mare e territorio sulla sua sinistra fino al Tagliamento.

Anonymous

1540-1550

ASVE, Savi e esec., dis., Livenza, 17

Mid-Cretaceous strata within the Tintina Trench, 3 km west of the community of Ross River, contain evidence of deposition in two distinct, alternating, fluvial settings. Coal-bearing, mud-dominated strata are commonly associated with high-constructive sandy channel systems, with extensive overbank, levee and splay deposits. Channels are between 3 and 30 m wide and 0.4–7 m thick. They show repetitive development of side and in-channel bar-forms, as well as up-channel widening of the rivers by selective erosion of associated overbank and levee deposits. Levees extended for several hundred metres away from the channels. In this setting low-angle inclined stratification and epsilon cross stratification may reflect lateral migration of crevasse channels or small streams. The paucity of exposure prevents recognition of the channels as products of multiple channel anastomosed systems or single channel high-constructive systems.

Gravel-dominated strata, inter-bedded with, and overlying coal-bearing units, are interpreted as deposits of wandering gravel-bed rivers, with sinuosity approaching 1.4. In most exposures they appear to be dominated by massive and thin planar-bedded granule to small pebble conglomerates, which would traditionally be interpreted as sheet-flood or longitudinal bar deposits of a high-gradient braided stream or alluvial fan. Architectural analysis of exposures in an open-pit shows that the predominance of flat bedding is an artefact of the geometry of the roadside exposures. In the pit the conglomerates are dominated by large scale cross stratification on a scale of 1–5.5 m. These appear to have developed as downstream and lateral accretion elements on side-bars and on in-channel bars in water depths of 2–12 m. Stacking of strata on domed 3rd order surfaces suggests development of longitudinal in-channel bar complexes similar to those observed in parts of the modern Rhône River system. Mudstone preserved in some of the channels reflects intervals of channel abandonment or avulsion. Minimum channel width is from 70 to 450 m.