As a contribution to the knowledge of historical rockslides, this research focuses on the historical reconstruction, field mapping, and simulation of the expansion, through numerical modelling, of the 30 September 1513 Monte Crenone rock avalanche. Earth observation in 2-D and 3-D, as well as direct in situ field mapping, allowed the detachment zone and the perimeter and volume of the accumulation to be determined. Thanks to the reconstruction of the post-event digital elevation model based on historical topographic maps and the numerical modelling with the RAMMS::DEBRISFLOW software, the dynamics and runout of the rock avalanche were calibrated and reconstructed. The reconstruction of the runout model allowed confirmation of the historical data concerning this event, particularly the damming of the valley floor and the lake formation up to an elevation of 390 m a.s.l., which generated an enormous flood by dam breaching on 20 May 1515, known as the “Buzza di Biasca”.
Massive rockslides and rock avalanches are natural events with high
destructive potential that can have a devastating impact on a territory's
economic and social fabric. Therefore, even if such phenomena are rare, they
cannot be considered negligible as natural hazards (Hungr and Evans, 2004).
The term
Considering the rockslides' and rock avalanches' distribution in the Alps (see von Poschinger, 2002), these phenomena seems to be more frequent in the central part of the Alps, particularly in the Pennine Alps and in the Lepontine Alps (between Switzerland and Italy), and in the Western Rhaetian Alps (between Switzerland, Italy and Austria), with regions classified according to the International Standardized Mountain Subdivision of the Alps (Marazzi, 2005). Considering the temporal framework of these events, several well-known rockslides fell during the modern and contemporary periods, i.e. after 1492 CE (e.g. Bonnard, 2006; von Poschinger, 2002): 1513, the Monte Crenone rock avalanche (Canton of Ticino, Switzerland); 1618, the Piuro rock avalanche (Province of Sondrio, Italy); 1806, the Arth–Goldau rock avalanche (Canton of Schwyz, Switzerland); 1881, the Elm rock avalanche (Canton of Glarus, Switzerland); 1987, the Val Pola rock avalanche (Province of Sondrio, Italy); and 1991, the Randa rock avalanche (Canton of Valais, Switzerland).
Although it may seem surprising, numerical modelling has focused on prehistoric (i.e. before the Roman period) rockslides and rock avalanches rather than on historical (since the Roman period, particularly those prior to the 20th century) events, perhaps because the most recent events are better documented or were directly observed. Staying exclusively in the Swiss Alps, recent reconstruction and modelling of prehistoric rockslides have concerned for example the Flims rock avalanche (Canton of Graubünden, ca. 8200 cal BP; von Poschinger, 2011), the Sierre rock avalanche (Canton of Valais, ca. 9550 cal BP; Pedrazzini et al., 2013) and the Chironico rock avalanche (Canton of Ticino, ca. 13 500 cal BP; Claude et al., 2014).
In order to contribute to the knowledge of historical rockslides, this research has focused on the historical reconstruction, field mapping, numerical modelling, and analysis of the geomorphological consequences of the Monte Crenone rock avalanche (MCRA) of 30 September 1513. These investigations also aim at improving the employment of historical and archaeological information in rock avalanche reconstruction and numerical modelling. Within this framework, the four objectives of this contribution include both the historical and geological reconstruction of the MCRA and the historical and geomorphological analysis of the consequences in the decades and centuries following the event and can be expressed as follows: (1) define the detachment zone and the perimeter and volume of the accumulation employing 2-D and 3-D Earth observations, as well as direct in situ field mapping; (2) reconstruct a post-event digital elevation model (DEM) based on historical topographic map analysis and a pre-event DEM by the subtraction of the fallen volume; (3) reconstruct the dynamics and runout of the MCRA thanks to a numerical model calibration; and (4) define the sediment cascade and budget generated by the MCRA, with particular interest in the damming of the valley floor and the subsequent Lake Malvaglia formation, which generated the enormous flood by dam breaching known on the southern side of the Alps as the “Buzza di Biasca” (for detail, see Sect. 2.1).
The MCRA, which occurred at the beginning of the modern period (1492–1798 CE) on
30 September 1513, was one of the biggest rock avalanches to have fallen on
the southern side of the Alps in historical times (von Poschinger, 2002;
Gruner, 2006). Generated from the collapse of part of the west
side of Pizzo Magn (2329 m a.s.l., also known as Monte Crenone), above Biasca,
it was at the origin of the most significant natural event that indelibly
marked the Ticino valley between Biasca and Lake Maggiore, the Buzza di Biasca of 20 May 1515 (Bonnard, 2004; Scapozza et al., 2015). The
tens of cubic hectometres of the rock avalanche deposit dammed the river Brenno in
the lower Blenio Valley (today's locality is named the Büza di Biasca) and
caused the formation of a temporary lake of 130 hm
The lower part of the Blenio Valley before the Buzza di Biasca of 20 May 1515, with the maximum extent of Lake Malvaglia formed behind the deposits of the MCRA of 30 September 1513. In the box at top right is the view from the north of the MCRA deposits as it appears today. Cartographic basis: National Map of Switzerland 1 : 25 000, © Swiss Federal Office of Topography swisstopo.
While there is little doubt about the precise date of the Buzza di Biasca (e.g. Viganò, 2013; Scapozza et al., 2015), the exact chronology of the MCRA is much more uncertain, probably partly as a consequence of the succession of events that occurred from the 13th century leading to the rock avalanche of the beginning of the 16th century (for a historical overview, see Scapozza et al., 2015; De Antoni et al., 2016). For several authors of the 18th and 19th centuries, such as Johann Jacob Leu, Johann Conrad Füesslin, Beat Fidel von Zurlauben, Johann Gottfried Ebel and Luigi Lavizzari (discussed in Bolla, 2010, and in Scapozza, 2014, with possible information transfer from one work to the other), the MCRA took place in 1512. Atanasio Donetti in 1860 and Alfonso Toschini in 1905, for whom the rock avalanche was generated by an earthquake, indicate the dates of 30 September 1512 and 16 October/30 November 1512, respectively (Bolla, 2010; Scapozza, 2014). Cesare Bolla proposed in 1889 the date of 28 September 1515 (Bolla, 1993), whereas according to Plinio Bolla other unspecified opinions placed the MCRA on 17 October 1511, 30 September 1512, 28 September 1513 or 30 September 1513 (Bolla, 1931).
The most evident traces of the MCRA are today visible in the lower part of the Blenio Valley, where the valley floor morphology is dominated by the impressive debris accumulation generated from the rock avalanche. These loose materials were exploited in the northern part of the accumulation, first as a quarry for inert material used mainly for the construction of the national highway crossing the Canton of Ticino from Chiasso to Airolo. In recent times, where the construction material had been removed in the past, the excavation materials from the New Rail Link through the Alps (NRLA, also known as AlpTransit) were deposited. The alluvial floodplain between Malvaglia and Loderio also formed after 1515 thanks to the accumulation of fluvial deposits coming from the river Brenno and the Orino and Lesgiüna streams; this sector is today known as “Bolla di Loderio” and is recognized in the Swiss federal inventory of alluvial zones of national importance (object no. 150).
Vom Rath (1862) described the MCRA as one of the major events of
its type in the Alps, covering a surface of almost 2 km
The structure of the deposits composed of several overlapped cones was
clearly recognized and described thanks to the boreholes drilled in the
deposits for characterizing materials in view of the construction of the A2
(E35) national highway (Hantke, 1983; Scapozza et al., 2015; De Antoni et
al., 2016), serving in the northern part of the MCRA deposit as storage of
the material excavated from the Gotthard Base Tunnel of the NRLA. A new
detailed description and interpretation of these borehole logs is discussed
in Sect. 4.2. These stratigraphical considerations are supported by
the recent documentation of a historical observation tower built in the
13th century (De Antoni et al., 2016): this tower, known as Torre di
Granono, was located in Loderio (Figs. 1 and 2), and its use allowed for
alerting the inhabitants of Montegnano, a hamlet of Biasca that was entirely
covered by the MCRA, and all inhabitants survived the event. The few historical
documents related to the MCRA (mostly written in Latin, collected and
discussed by De Antoni et al., 2016) tell us about the event that (1) the
MCRA fell in non-rainy weather (“
Digital mapping was based on both 2-D and 3-D Earth observation, as well as
on direct in situ field mapping. The 2-D Earth observation was based on the
joint analysis of three base images (for details, see Ambrosi and Scapozza,
2015): (1) hillshade generated for various exposition-angles from the
swissALTI3D DEM, which has a pixel resolution of 2.0 m and an accuracy of
The mapping was performed according to the legend for the Geological Atlas of Switzerland 1 : 25 000 (OFEG, 2003; Wiederkehr and Möri, 2013; Ambrosi and Scapozza, 2015).
Geographical information systems (GISs) highly facilitate the integration of
historic landscape patterns in actual topographical maps (e.g. Kienast, 1993; Stäuble et al., 2008; Scapozza, 2013).
The reconstruction of the MCRA accumulation before its exploitation in the
20th century was based on the georeferentiation of the oldest detailed
topographical representation of the rock avalanche accumulation: the
original relief (
The first modern topographical representation of the MCRA, falling from the west side of the Pizzo Magno (alternatively called Pizzo Magn)); the accumulation is visible on the valley floor between Biasca and Loderio. Extract from the original relief for the Dufour Map (Kündig and Müller, 1854), drawn by Andreas Kündig and Benjamin Müller in 1854. © Swiss Federal Office of Topography swisstopo. A comparison with the actual topography is possible by observing Fig. 1.
The numerical analysis of the MCRA focuses on the runout
representation and does not concern the rock slope stability analysis
prior to the failure, since the latter does not determine a highly
relevant element for the flow dynamics and deposition. The runout analysis
has been performed using the 2-D numerical simulation software RAMMS (Rapid
Mass Movement Simulation) DEBRISFLOW module, developed by the WSL
Institute for Snow and Avalanche Research SLF (Christen et al., 2012) and obtainable
on request via the RAMMS website (RAMMS rapid mass movements website, 2019). This
software has been chosen because of its application of modelling rock
avalanches to three cases of historical rockslides in the Canton of Ticino
(Steinemann, 2012a, b, c). RAMMS utilizes the Voellmy frictional law, which
applies two friction parameters to represent the frictional resistance (Pa)
(see Salm, 1993; Salm et al., 1990): the dry Coulomb-type friction
(coefficient
In the
Before calibrating the cited parameters, the model needs as input data a DEM of the pre-failure surface and the mobilized mass volume. The latter was obtained directly by numerical modelling on the basis of the deposition results. The release volume does not represent the actual geometry of the collapsed body. Instead, it is defined by a fictitious release area combined with a release depth inside the Release Tab.
The mapping at a scale of 1 : 10 000 highlights the deposits' nature, recognized through the field surveys and the geomorphological elements already mapped in the SUPSI landslide inventory map of the Canton of Ticino.
The trace of the MCRA on the bottom of the lower Blenio Valley consists of impressive, well-recognizable debris accumulation at the mouth of the Crenone Valley (see Sect. 2.1). In particular, along the right side of the Crenone stream, from the MCRA debris cone summit (Pt. 1 in Fig. 3) toward the west, a roughly 700 m long and 10–30 m high morphological crest dominates the landscape (Fig. 4c). This crest is characterized by sub-angulated grain-supported boulders of augen gneiss and leucocratic gneiss of the Simano nappe, exceeding 1 m in diameter (Fig. 4e). Again on the Crenone stream's right side, the deposit persists further east inside the Crenone Valley and traces the altitude limit of the MCRA flow (Pt. 2 in Fig. 3). At the opposite side of the Crenone stream (Pt. 3 in Fig. 3), the MCRA deposit appears to be more distributed over the slope (Fig. 4f) and maintains the size and lithology but shows a higher percentage of matrix. Outward from the cone, both the deposits continue with a smaller slope gradient.
Part of the MCRA deposit is also recognizable along the river Brenno's right side (Chiegnezz locality, Pt. 4 in Fig. 3; Fig. 4d), where it reaches an altitude of 420 m a.s.l. The material is constituted by a massive diamicton, matrix supported (lithofacies code Dmm), composed of sub-angulated clasts of augen gneiss and leucocratic gneiss within a very well graded silty sand (20 % fine) of light beige colour (Prandi, 2018). In this area, the erosional action of the Buzza is well visible on a gradient change, from the original deposit altitude (420 m a.s.l.) to the river Brenno altitude (350 m a.s.l.).
In the northernmost area (Pt. 5 in Fig. 3), the MCRA deposit is deeply reshaped by the succession of works, starting with the excavation of inert material used mainly for the construction of the national highway and, in earlier times, the deposition of materials coming from the NRLA.
Along the Crenone riverbed, the deposit derives from the torrential and debris flow transport subsequent to the MCRA.
The attempt to recreate the MCRA pre-failure morphology of the Blenio Valley (pre-failure surface in the following sections) is the major challenge of this study. As no maps are available prior to the mid-19th century (see Sect. 3.2), information about the deposit thickness and extension derives from the boreholes completed during the geotechnical studies performed for the construction of the national highway A2 (E35) and from the remaining in situ MCRA deposits.
Borehole data were extracted from the GESPOS (Gestione Sondaggi, Pozzi e Sorgenti) database (managed by the SUPSI Institute of Earth Sciences) containing drilling data, well logs and springs in the Canton of Ticino territory. From the five boreholes completed in 1974, the three boreholes identified through GESPOS, IDs 701.27, 701.31 and 701.30, are located in the northernmost deposit portion and allow the quantification of the deposit thickness at their sites (Fig. 3). Because the boreholes were drilled in 1974, the shown thicknesses are reduced compared to the original MCRA deposit, which was not eroded by the Buzza di Biasca of 1515. Borehole 701.27 shows 24.2 m of coarse deposits that could be attributed to the MCRA on the basis of the grain size and on the depositional facies (Fig. 5a). Borehole 701.30 presents 13.5 m of deposits attributed to the MCRA (Hantke, 1983) (Fig. 5b). According to the comparison with the historical topographical maps of the second half of the 19th century (Fig. 2), the extra deposit thickness in borehole 701.30 could reach an altitude of about 420 m a.s.l.; the total deposit thickness associated with the MCRA could be estimated to be about 30 m (Fig. 5). Borehole 701.31 drilled in the most distal part of the cone shows an erosion of the MCRA accumulation of about 30 m, considering the original deposit altitude of 390 m a.s.l. (Fig. 5c). Considering the 13.85 m of rock avalanche deposit in this location, the original deposit thickness just after the MCRA falling was probably at least 40 m.
Geomorphological map of the lower part of the Blenio Valley, reporting the morphostructures and deposits associated with the MCRA of 1515 and following events. Cartographic basis: National Map of Switzerland 1 : 25 000, © Swiss Federal Office of Topography swisstopo.
Field photographs of the current situation of MCRA morphostructures
and deposits.
Stratigraphy of GESPOS boreholes 701.27, 701.30 and 701.31 drilled on the Monte Crenone debris cone.
The incised MCRA deposit along the river Brenno's right side is the only information on the deposit thickness in the western part of the accumulation area (Fig. 4d) and provides a key element to understanding the MCRA flow. Indeed, its extension and position force us to think of strong downstream path curvature. Flow propagation following the valley axis would provide too much deposition upstream, not supported by the current geomorphological evidence. According to the field and borehole evidence, the best pre-failure MCRA Blenio Valley surface was selected by performing several numerical models and evaluating which pre-failure surface could better host the failure mass. The final pre-failure surface shown in Fig. 6 represents a debris cone that is clearly smaller than the current one. The central cone section shows a 900 m long, 30 m high morphological crest covering the easternmost part of the current crest described in Sect. 4.1. This geomorphological element channelled the MCRA flow southward in agreement with the field observations and suggests a strong erosional activity prior to the MCRA. Finally, the pre-failure contour surface on the river Brenno's right side removes the MCRA deposit and has been tracked considering the steep slope morphology.
Contour lines of the lower part of the Blenio Valley as reconstructed for the pre-MCRA falling. Cartographic basis: hillshade derived from the swissALTI3D digital elevation model, © Swiss Federal Office of Topography swisstopo.
The numerical modelling of the MCRA has the aim of identifying a best-fit simulation in terms of runout propagation, distribution, deposit thickness and flow velocity plausibility. The attempt to reproduce the MCRA through numerical modelling meets strong criticism, and unavoidable simplifications have to be adopted. The first criticism, as mentioned in Sect. 4.2, derives from the lack of knowledge of the exact morphology preceding the 1513 event. The suggested shape and depth of the pre-failure surface under the MCRA deposit is not confirmed by any data in the central and southern part of the cone. Consequently, the numerical modelling parameters assume a considerable margin of variability. Furthermore, no data on the event dynamics and timing exist.
With respect to the pre-failure surface, a 10 m DEM resolution has been
considered suitable for the model's needs to run the simulation. Considering
the uncertainty of the reconstructed surface, a higher resolution would not
bring more accurate results regarding the phenomenon veracity. For the flow
density, the value of 2500 kg m
The numerical simulation represents the MCRA as a single event. The difference in the altitude of the path associated with a narrow valley on a reduced path acts on the strong energy of the phenomenon. The high turbulence shown in the numerical modelling is confirmed through the relatively small size of the boulders (metric diameter) in relation to the volume of the deposit (Fig. 5e, f).
The flow height shown in the numerical modelling finds agreement with the NNE–SSW accumulation on the Crenone Valley's right side (Fig. 8c), passing by the deposit (Pt. 2 in Fig. 3), and the flow motion 110 s after the initial collapse is plausible.
Several attempts to model the MCRA by varying the
Results of the numerical modelling of the MCRA, with the representation of flow heights every 20 s (30 s for the last image). Cartographic basis: hillshade derived from the swissALTI3D digital elevation model, © Swiss Federal Office of Topography swisstopo.
The final model attributes a calibrated deposit volume of 85.5 hm
The MCRA accumulation surface obtained by numerical modelling added to the pre-failure DEM.
Table 1 shows a comparison among the RAMMS::DEBRISFLOW modelling calibrations performed on the MCRA and three other case studies on rockslides in the Canton of Ticino. The models proposed by Steinemann (2012a, b, c) were performed to find optimal input parameters to use RAMMS for hazard prediction for an unstable slope in the Maggia Valley. A clear difference between the MCRA modelling parameters and the other case studies is present. Utilizing the Preonzo rockslide dataset on the MCRA case, the model shows a runout that is twice more extended than the real case and a failure time of 32 min. The difference between the RAMMS models parametrization proposed by Steinemann (2012b) in his case studies and the MCRA model could be related to the huge difference in the volume magnitude and the path. Indeed, if for the Sasso Rosso, Preonzo and Cè rockslides, the accumulation is not constrained by the topography, the path is tightened at the mouth of the Crenone Valley for the MCRA.
This particular morphological conformation associated with the large volumes involved gives the movement a very particular kinematics with associated high turbulence.
Examples of RAMMS::DEBRISFLOW software parametrization for rockslides in the Canton of Ticino.
The reconstruction of the MCRA runout model allowed us to confirm the
historical data about this event, in particular the damming of the valley
floor up to an elevation of 390 m a.s.l. and the subsequent creation of a lake
which reached a maximum extension of 4.5 km and 130 hm
The runout model of the Buzza di Biasca considers an occurrence of the
breakage shortly after the lake overflow, with subsequent triggering of a
sudden chain reaction (Scapozza et al., 2015; De Antoni et al., 2016). The
Buzza di Biasca simulation indicates a flood peak at the breach of about
50 000–60 000 m
If the historical and territorial consequences of the extreme flood generated by the collapse of the dam constituted by the MCRA accumulation are well known (e.g. Pometta, 1928; Galli, 1937; Solari, 1982; and Colombo, 1999, and their summary and critical analysis in Scapozza et al., 2015, and De Antoni et al., 2016), less information is available concerning the sedimentary and morphological impact of this event. Recent investigations carried out into the fluvial morphology of the river Ticino floodplain and delta between Bellinzona and Lake Maggiore indicate, as a consequence of the Buzza di Biasca of 1515, the following: (1) the migration of the Ticino river mouth from the south to the north, (2) the rapid progradation of the Ticino river delta and (3) the fluvial metamorphosis of the river Ticino from a meandering to a braided morphology (for a detailed analysis of these three main points, see Scapozza, 2013; Scapozza and Oppizzi, 2013; Scapozza and Ambrosi, 2021).
The Riviera valley floor between Biasca and Lodrino in 1785.
The fluvial metamorphosis probably also concerned the floodplain of the river Ticino between Biasca and Bellinzona, as seems to be indicated by a recently rediscovered topographic map of the valley floor between Biasca and Lodrino in 1785, conserved in the historical archive of the Biasca municipality (Fig. 10a). The river morphology is braided, even if the probable original meandering morphology is still well recognizable, with the gravel bars linked with the meanders' migration (Fig. 10b). The most recent channels mainly affect the alluvial forest, indicating that their origin must have been relatively recent (perhaps on the order of several centuries). West of Biasca, two palaeo-channels of the river Ticino are clearly recognizable and are marked on the maps as “Ramo mairano” (from the locality of Mairano, near Iragna) and as “Letto vecchio” (literally “old riverbed”). Between Pasquerio and Mairano, the river Ticino did not flow completely on the right side of the valley floor as it did after its correction at the beginning of 20th century but in a more central position (Fig. 10c).
Compilation and calibration of radiocarbon ages discussed in the
text. Calibration was performed with OxCal 4.4 software, using the IntCal20
curve and with a
Chronostratigraphic evidence of the sedimentary effect of the Buzza di Biasca on the river Ticino floodplain is very limited. It indicates a
very limited fluvial deposit input on the floodplain (
Sedimentation rates on the Ticino floodplain during the period including the Buzza di Biasca event, quantified thanks to the radiocarbon dating presented in Table 2. Sources are (1) Scapozza et al. (2017), (2) Scapozza and Oppizzi (2013), (3) Donati (1969), and (4) Donati (1999).
Five main conclusions can be drawn from the observations and modelling of the MCRA event:
Geological observations (in particular the stratigraphy of boreholes
crossing the MCRA deposit) as well as the historical sources (in particular
the existence of the Granono tower) indicate a series of collapses from
the Monte Crenone that began at least as early as the 13th century, leading
to the main rock avalanche of 30 September 1513, with a reconstructed volume
of about 85.5 hm The MCRA modelling thanks to the RAMMS::DEBRISFLOW module allowed for a precise
reconstruction of the event and of the accumulation volume and geometry. It
was possible in particular to determine a slight rise in the rock avalanche
front on the right-hand side of the Blenio Valley, where even today there is
a clear morphological trace of this event, and the damming of the valley floor up to
an altitude of 390 m a.s.l., which corresponds with the maximum level of Lake
Malvaglia just before the triggering of the Buzza di Biasca of 20 May
1515. The comparison of MCRA modelling with other case studies modelled in
the Lepontine Alps indicates lower values of the dry Coulomb-type friction
(coefficient The damming of the valley floor exercised by the MCRA accumulation up to an
elevation of 390 m a.s.l. allowed the creation of a lake which reached the
maximum extent of 4.5 km and 130 hm The MCRA, the subsequent creation of Lake Malvaglia and the sudden
collapse of the dam triggering the Buzza di Biasca can be considered
a sedimentary cascade originating from two very high magnitude events. Although the
direct impact on the sedimentation of the floodplain indicates very limited
fluvial deposit input related to the Buzza di Biasca, the
morphological effect of this event was evident in the floodplain in the following
centuries. Among the most important effects are the migration of the Ticino
river mouth from the south to the north, the rapid progradation of the
Ticino river delta and the fluvial metamorphosis of the river Ticino from a
meandering to a braided morphology. This indicates that the MCRA generated
geomorphological consequences that affected the Ticino valley as far as Lake
Maggiore. The reconstruction of large historical rock avalanches such as the MCRA
allows the parametrization and validation of numerical models, which can be
applied to the forecasting of today's unstable zones that present similar
geological and structural characteristics and have not already collapsed.
These models are also significant for the correct interpretation of the
chain of territorial consequences of large rockslides, affecting the
valley floor (or even the lakes) located downslope of the sector directly
impacted by the event. In this framework, they are of interest not only in
the field of geosciences but also for a better comprehension of the
historical and socio-economic consequences of these major natural events.
The code is not made accessible by the software developer because RAMMS::DEBRISFLOW is commercial software.
Research data can be accessed through the SUPSI Instory (SUPSI INSTitutional repositORY), the online institutional archive of publications of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI), at the following link
Investigation and formal analysis for MCRA mapping and modelling were performed by ADP and supervised by CA. Investigation and formal analysis for the MCRA geo-historical framework, as well as for Buzza di Biasca consequences, were performed by CS. ADP and CS prepared the manuscript with contributions from CA.
Cristian Scapozza is one of the two associated editors for the theme issue “Geomorphology and society”. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.
Publisher’s note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
An anonymous source provided the translation from Latin of the document written by Giovan Battista Pellanda and the topographical map of Riviera in 1785. The manuscript was substantially improved thanks to the two anonymous reviewers.
This paper was edited by Nikolaus J. Kuhn and reviewed by two anonymous referees.