P13_copertina_R_OK C August 20-28,2004 Florence -

Field Trip Guide Book - P13 Post-Congress G. Larini,M.Pizziolo Associate Leaders:M.T. DeNardo, Leader: G.Bertolini EMILIA APENNINES LANDSLIDES OFTHE 32 Volume n°3-fromD01toP13 GEOLOGICAL CONGRESS nd INTERNATIONAL P13 14-06-2004, 14:29:46 The scientific content of this guide is under the total responsibility of the Authors

Published by: APAT – Italian Agency for the Environmental Protection and Technical Services - Via Vitaliano Brancati, 48 - 00144 Roma - Italy

Series Editors: Luca Guerrieri, Irene Rischia and Leonello Serva (APAT, Roma)

English Desk-copy Editors: Paul Mazza (Università di Firenze), Jessica Ann Thonn (Università di Firenze), Nathalie Marléne Adams (Università di Firenze), Miriam Friedman (Università di Firenze), Kate Eadie (Freelance indipendent professional)

Field Trip Committee: Leonello Serva (APAT, Roma), Alessandro Michetti (Università dell’Insubria, Como), Giulio Pavia (Università di Torino), Raffaele Pignone (Servizio Geologico Regione Emilia-Romagna, Bologna) and Riccardo Polino (CNR, Torino)

Acknowledgments: The 32nd IGC Organizing Committee is grateful to Roberto Pompili and Elisa Brustia (APAT, Roma) for their collaboration in editing.

Graphic project: Full snc - Firenze

Layout and press: Lito Terrazzi srl - Firenze

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32nd INTERNATIONAL GEOLOGICAL CONGRESS

LANDSLIDES OF THE EMILIA APENNINES ()

AUTHORS: G. Bertolini1, M. Pizziolo2 LEADER: G. Bertolini1 ASSOCIATE LEADERS: M.T. De Nardo2, G. Larini3, M. Pizziolo2

1Regione Emilia-Romagna, Servizio Tecnico dei bacini Enza e Sinistra - Italy 2Regione Emilia-Romagna, Servizio Geologico, Sismico e dei Suoli - Italy 3Regione Emilia-Romagna, Servizio Tecnico dei bacini Taro e Parma - Italy

“DIREZIONE GENERALE AMBIENTE, DIFESA DEL SUOLO, DELLA COSTA E PROTEZIONE CIVILE. Servizio Geologico, Sismico e dei Suoli. Servizio Tecnico bacini Enza e sinistra Secchia”

Florence - Italy August 20-28, 2004

Post-Congress P13

P13_R_OK A 25-05-2004, 13:26:31 Front Cover: The landslide is the oldest among those dated in the Province. It formed from the Late-glacial to the Subboreal period, but several parts of it are still active today.

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Leader: G. Bertolini Associate Leaders: M.T. De Nardo, G. Larini, M. Pizziolo

Introduction Even before the Landslide Inventory Map, the The Emilia-Romagna Region is one of the Regional Geological Survey was a national leader most landslide-prone territories in the world. in the study of landslides and their distribution. In Approximately 20% of the mountainous terrain is the 1980s a survey was performed for the 1:10.000- subject to the risk of landslides. scale regional geological cartography project. The Almost 99% of present-day landslide activity is due to detailed scale of this map allowed data from about the reactivation of pre-existing landslide bodies. 32.000 landslides to be collected. Under pressure Reactivation is a key-concept which must be from renewed public awareness, much work has been addressed. accomplished during the last decade. In addition, Since medieval times, 2000 villages in Emilia- events occurring in this time period have been studied Romagna have been built upon or very close to (a synthesis is found in Bertolini et al., 2001). A dormant landslides, despite the recurrent damage historical database of landslide events has been set which was infl icted upon some of them. up and some thousand records have already been After WW II, these villages expanded during the collected for the National Inventory of Landslides ensuing economic boom, without regard for such (IFFI) project. “minor” problems as landslides. This urban expansion continued into the 1970s and 1980s, when the climate The aim of the fi eldtrip is to show and explain was generally milder and landslide reactivation events experiences with landslides occurring within the infrequent. region. Geological and environmental conditions People, swept up by their new-found wealth, lost leading to instability will be described. Discussion some of their historical memory. Houses and factories will be encouraged especially regarding the role were built upon the fl atter, wider and apparently stable of mathematical modelling, cartography, historical portion of slopes …. which instead often turned out to research, monitoring and remote-sensing, as applied be the feet of dormant landslides! to landslide hazard evaluation. An awareness of landslides on the part of the regional administration, the media and the public, was fi nally References heightened in 1994 with the Corniglio landslide. This guide contains both original unpublished data This landslide was reactivated after one century of and references to recent publications. The main dormancy as it completely destroyed the hamlet of sources are: Linari (70 houses and industrial buildings). • Bettelli and de Nardo (2001) for the geological Since then, this region’s territory has been affected setting of marine units; several times (in 1996, 2000 and 2001) and some • Bertolini G. and Pellegrini M. (2001) for other hamlets have been either destroyed, severely historical data, radiocarbon dating and statistics damaged or threatened. about landslides; In Emilia-Romagna there have been no casualties, • Bertolini G., Canuti P., Casagli N., De Nardo but the economic costs and the repercussions upon M.T., Egidi D., Mainetti M., Pignone R. and industrial development have been heavy. The costs Pizziolo M. (2002) for cartography. of reconstruction and consolidation works have amounted to several hundreds of millions of Euros. A simple Glossary of Italian terms These costs have been entirely covered by the national Frana: how is it defi ned? Frana in Italian is a and regional governments. comprehensive term for any mass of rock, debris or DO1 to P13 n° 3 - from Volume In order to confront this problem, the Emilia-Romagna soil moving under the force of gravity, independent Geological Survey developed a new and detailed of the mechanism or the volume involved (sinkholes “Landslide Inventory Map” starting in the mid-1990s. are included). Frana is derived from the Latin noun This map is a powerful tool: it was immediately put to “frangina, ” which in turn is derived from the verb use in new territorial and urban planning. On the basis “frangere,” which means “to break.” of the new cartography, Emilia-Romagna became the The use of this term is widespread in all Italian fi rst Italian region to enforce rules and obligations regions, although several local dialect terms exist: addressing landslide hazard reduction. “lama,” “lezza,” “lavina”, “rovina,” and “ruina.” In

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particular, this last term is quite old: it was used in the Thetian basin closed due to continuous convergence written form in Dante’s “Divina Commedia” (Inferno, between the European and the Adriatic plates. First, XII, 4-9, 28-30) in reference to a large rockslide near in the Early-Middle Eocene, the subduction of oceanic Rovereto in the Adige Valley (“la grande ruina”). crust produced an accretionary prism of sediments. A list follows of the most commonly used specifi c After the oceanic crust was completely consumed, landslide classifi cations. But remember! Rarely is the ongoing collision between the two continents there a perfect correspondence between the Italian produced three broad allochthonous assemblages and English terms. The translations of Cruden & which correspond to three distinct paleogeographic Varnes’ defi nitions are not defi nitive and often are a domains (from internal to external): Ligurian, Sub- cause of endless debate! You can fi nd a more detailed Ligurian and Tuscan-Umbria-Romagna (Figure 1 discussion in Canuti & Esu, 1995. and 2). The Tuscan Units formed a fold-and-thrust belt which The more specifi c terms about landslide was then buried by the Ligurian and Sub-Ligurian classifi cation are: Nappes, both moving toward the NE. The Tuscan • referring to the landslide mechanism: Colata di Units are now partially exposed in a few tectonic terra (Mudslide, Mudfl ow), Colata rapida di windows (Mt. Zuccone, Gova, etc.) and on the ridge detrito (Debris fl ow), Scivolamento (Sliding), of the Apennine chain. Scivolamento traslativo (Translational slide), The relatively more allochthonous Ligurian Nappe Scivolamento rotazionale (Rotational slide), consists of the uppermost structural units and is Crollo (Fall), Ribaltamento (Toppling), well-exposed in the Emilian Apennines, from Smottamento (Land, Soil slip), Espansione Pavia to the Bologna Apennines. Its basal contact (Spread), Sprofondamento (Sinking); upon the Umbria-Romagna units is evident in • referring to the material involved: Suolo (Soil), outcrops along the transverse “Sillaro Line”. As a Terra (Earth), Detrito (Debris), Roccia (Rock), consequence of the Early-Middle Eocene closure of Substrato (Bedrock); the Ligurian oceanic basin, sediments which compose • referring to the state-of-activity: Attiva (Active), the semi-allochthonous “Epi-Ligurian sequence” Quiescente (Dormant), Inattiva (Inactive), were deposited in “satellite” basins, just above Sospesa (Suspended), Relitta (Relict). the Ligurian Nappe. The deposition of terrigenous sediments in the Plain foredeep from the Late Regional geological setting Miocene-Pliocene to the Quaternary ended the period A little over half of the land surface in the Emilia- of marine sedimentation in the Apennines. Romagna region is covered by the Apennine mountain chain. This mountainous region extends Tuscan-Umbria-Romagna Units from the Apennine ridge (in the SW part of the These are the deepest occurring sedimentary rocks in region), reaching elevations of 2165 m a.s.l. (Mt. the Northern Apennine mountain chain and may be Cimone in the province of ), to the pede- subdivided into three sequences: the Metamorphic Apennine margin (in the NE) which ranges from 100 Tuscan Sequence, the Umbria-Romagna Sequence to 200 m a.s.l. The “Emilian Apennines,” where the and the Tuscan Nappe Sequence. The fi rst stage of fi eldtrip takes place, are the main subject of this paper. sedimentation is common to all these sequences. They are located in the southern part of the Bologna, The deposition upon the crystalline Palaeozoic Modena, Reggio Emilia and Parma provinces. basement began in the Middle-Late Triassic with The main reference for the description of the the “Verrucano” unit (alluvial, lagoonal, shallow geological setting is the 1:10,000-scale Geological marine coarse sediments), followed by the Late Map that was produced by the Regional Geological Triassic “Gessi Triassici” unit (evaporites), then by DO1 to P13 n° 3 - from Volume Survey, and the map synthesis at a scale of 1:50,000, Late Liassic carbonate shelf deposits and, in turn, by commissioned by the National Geological Survey various pelagic units from the Late Liassic to Early to the Regional Administration and now in press. Oligocene in age. The foredeep clastic turbidites of Both projects were conducted in collaboration with the Macigno-Falterona-Trasimeno sequence (Late university departments and research institutions. Oligocene to Aquitanian in age) fi nish off the Tuscan The Northern Apennines are a fold-and-thrust post- Nappe Sequence. Outside the study area, in the collisional belt, built-up during the Tertiary as the Umbria-Romagna sector, sedimentation continued until the Late Miocene with slope mudstones

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and a foredeep turbidite sequence assigned to the interbedded turbiditic sandstones (the Petrignacola “Marnoso Arenacea Formation.” Deposition of the and Ponte Bratica Formations). Metamorphic Tuscan Sequence probably fi nished in The Sub-Ligurian sequence also crops out in tectonic the Late Oligocene with the “Pseudomacigno,” since windows beneath the overlying Ligurian Nappe (at this is buried beneath the Tuscan Nappe. Mt. Zuccone, Bobbio). In the study area, only a few units belong to the Tuscan Nappe outcrop. These outcrops are evident Ligurian Units in the upper part of the mountain chain: they are the These are deep-sea sediment sequences which are Late Macigno and Gessi Triassici Formations. Jurassic to Early Eocene in age. They are subdivided into many different local sequences that share major Sestola-Vidiciatico tectonic Units features: in the lowest part of the sequences, Early In the fi eld-trip area other Miocene clastic turbidites and Late Cretaceous clayey complexes (“Complessi (the Mt. Cervarola, Mt. Modino-Mt. Ventasso Units) basali”) are composed of calcareous or arenaceous are present. They fi lled the foredeep basins situated turbidites (“Argille a Palombini”, “Arenarie di Ostia”) at the front of the Ligurian and Sub-Ligurian Nappes and multicoloured shales (“Argille Varicolori”). and are frequently associated with chaotic melanges All these formations exhibit a block-in-matrix composed of materials derived from the Sub-Ligurian, texture due to the effects of continuous and intense Ligurian and Tuscan Sequences. These chaotic tectonic stresses which almost destroyed the original assemblages are considered to be one distinct tectonic well-layered lithology. Because of this textural unit that overthrust also the foredeep sediments (i.e. feature, these units were grouped together under Cervarola Formation) during its deposition. the comprehensive term “Argille Scagliose” (“scaly clays”), and then the term “Complesso Caotico” Sub-Ligurian Units (“Chaotic Complex”) until the late 1970s. This sequence mainly constists of Paleocene- The units are now considered to be tectonic melanges Middle Eocene shaly-calcareous turbidites (the (fragments of formations and olistostromes), in which Canetolo Complex). The upper part of the sequence, the common block-in-matrix feature was acquired Late Eocene-Early Miocene, is also made up of during formation of the accretionary prism during Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 2 - Geological cross-section of the Emilia Apennines

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the Late Cretaceous to Early Eocene. The degree with the exception of the already mentioned clayey of tectonisation is very intense, with shear surfaces breccias and olistostromes which are present at two observable at all scales. levels of the sequence (in the Middle Eocene and All these chaotic units are usually referred to as the Late Oligocene-Burdigalian). These chaotic “Basal Complexes.” They are overlain by a thick Epi-Ligurian Units are quite similar to the Ligurian series of more coherent Late Cretaceous to Early Units, also from lithological and geotechnical points Tertiary calcareous or arenaceous turbidites known of view. as “Helmintoid Flysches.” These form wide, thick and less-deformed slabs, lying on top of the basal Marine units of the Apennine margin complexes. This layered structure is usually well- A sequence of marine terrigenous sediments fi lled preserved. Physical weathering processes make the youngest foredeep, during the Late Miocene these formations susceptible to erosion and landslide to Pleistocene. The sequence commences with processes. Messinian evaporites (“Gessoso Solfi fera”), related We estimate that almost two-thirds of all the to the Mediterranean desiccation event, overlain landslides occurring in Emilia-Romagna originate by continental, brackish water clastic deposits (the within Ligurian units. “Colombacci” Formation). These deposits are in turn overlain by deep-water Early Pliocene to Early Epi-Ligurian Sequence Pleistocene blue clays (“Argille azzurre”). After the closure of the Ligurian oceanic basin, a The blue clays outcrop along the Apennine margin and thick sequence of sediments was deposited in marine plunge gently northward underneath the regressive basins (“satellite basins”) lying at fi rst upon the sands and the Po Plain continental infi ll. The so- already deformed accretionary prism, and then upon called “Intra-Apennine Pliocene” is an exception: it the translating Ligurian Nappe. is a large slab of Pliocene blue clays and sands, gently These sedimentary sequences were deposited from synclinal in shape, located in the Bologna Apennines the Middle Eocene to the Early Messinian. In the and physically separated from the corresponding lower part of the sequence argillaceous breccias and “blue clays” of the margin. olistostromes were deposited as a result of mud fl ows and debris fl ows (Bettelli & De Nardo, 2001). They Quaternary continental deposits were formed by reworked materials coming from the Alluvial deposits: gravel deposits are in the valley front of the Ligurian Nappe. bottoms, independent of bedrock type and basin The “normal” sedimentation commences with hierarchy. The deposits are a results of the worst deep-water shale and turbidites (the Monte Piano historical and pre-historical climatic periods as, for and Loiano Formations, Middle to Late Eocene) example, the recent Little Ice Age from 1500 to followed by muddy and sandstone turbidites 1850 B.P. and the Last Glacial Age from 75,000 to (the Ranzano Formation, Early Oligocene), by 11,500 yr. B.P. The lithosomes that fed these deposits hemipelagic slope deposits (the Upper Oligocene- were mostly the bases of numerous landslides which Burdigalian Antognola Formation) and, in turn, were eroded by the hydrographic network. Peat and by Miocene shallow-water (sandstone) and slope lacustrine clay lenses are often found interbedded with (marls) sediments (the Bismantova Group). The clay coarser fl uvial sediments, attesting to ancient landslide of the Termina Formation (Late Serravallian to Early dams. A clear, modern example of this phenomenon is Messinian) tops the Epi-Ligurian Sequence. Huge found on the Secchia River: a landslide dam occurred lenticular units consisting of clay-supported breccias in 1960 A.D. and formed a lake about 26 km2 wide. (i.e. Canossa Olistostrome) are interbedded in the Within a three-month interval, more than 5 metres of Antognola Formation. These are made up of reworked clay was deposited on the valley fl oor. DO1 to P13 n° 3 - from Volume Ligurian materials. After the end of the Last Glacial Age, moraines As a consequence of their different depositional became important sources of gravel that fed the history, the Epi-Ligurian Sequence and the Ligurian alluvial deposits on the valley fl oors. Gravel alluvial Units show remarkably different degrees of terraces of fi ve to six different orders are found on deformation. The Epi-Ligurian Sequence forms the present-day hillsides, at elevations of tens of thick, fl at, horizontally-bedded, gently-folded slabs; it metres above the existing riverbeds. They are relics of lies on top of the more deformed Ligurian complexes. previous valley fl oors and attest to the recent, actual These rocks are very resistant to weathering processes, uplift of the mountain chain.

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini by moreresistantslabsofHelmintoidFlyschesor Ponte Bratica,” “Argille” and“Calcari”) areoverlain Varicolori”) orSub-Ligurian units(i.e.“Arenarie di Basal Complexes (i.e.“Argille aPalombini,” “Argille 1000 m,amoregentle,hillyaspectprevails: Ligurian Formation) along thesteepandrocky slopes.Below prevails. Tertiary sandstonesoutcrop(i.e.theMacigno along themountainchain’s crest,themountainchain different landscapetypes. Above 1000minelevation, The Emilian Apennines canbedivided intotwo landscape The Apennine exposed toweatheringprocesses,causesthis. consequently thenarrowness ofthestratumrock a few decimetresofsoil. Weak permeability, and are oftenvisibleinoutcroporburied underonly Ligurian Unitsdonothave considerablecover and Usually, theLigurianBasal Complexes andSub- eluvial cover isoftenthicker than1meter. their highcarbonaceouscontentandconsequentlythe prone tochemicalweatheringprocessesbecauseof Epi-Ligurian UnitssuchastheBismantova Groupare and landslideactivity. several metresandarefrequentlyaffected bycreep eluvio-colluvial depositsmayreachthicknessof susceptible tophysicalweatheringprocesses. The Cretaceous HelmintoidFlysches,andthey arevery which areoftenmesa-shaped,composedofLigurian deposits arealmostalways presentontheslabs, including freeze-thaw cycles. The eluvio-colluvial is directlyexposed tophysicalweatheringprocesses the Macigno,Cervarola, orModinofl upper chainwhere Tertiary sandstoneoutcrops(i.e. deposits, ispresent. The formerisfrequentinthe consisting ofcoarsedebrisandeluvio-colluvial Slope-deposits (Larini etal.,2001). attested tobytheCedraandParma Valley glaciers and thatthey rarelyextended below 900m.a.s.l.,as that onlyafew, smallglacialtongueswerepresent, basis ofageomorphologicreconstruction,weknow snowline rangedfrom1300to1200ma.s.l.Onthe was reached18,000to20,000yearsago,whenthe Phase” inthe Apennines, afterLarinietal.,2001) America. The LastGlacialMaximum(“Val Parma Würm phaseofthe Alps and Wisconsinian inNorth 75,000 to11,500yrs.B.P. Itcorrespondstothe ascribed totheLastGlacial Age thatlastedform catchment basins. The Glacialdepositsareusually the upperParma, Enza,SecchiaandPanaro Rivers on thehighestpartsofridgeandparticularlyin Moraines : Glacialcirquesandmorainesarefound : Quaternarycontinentalcover, yce) and ysches),

literature thesehave oftenbeencalled is alsousedforthesematerials.Inthegeological evident slickensides. Indeed,theterm “scalyclays” one centimetre. The lensesorscalesareboundedby marl, isontheorderofonemillimetre(orless)upto the shearedlensesofclay, clayshales,marlyor The sizeoftheclasticfragmentaggregates andof (occurring intectonicorsedimentarymélanges). structure, sometimeseven atamicroscopicscale units isacomplex anddisarrangedoreven chaotic The clearestfeatureofthemostlandslide-pronerock landslide-prone rockunits Lithologic andgeotechnicalfeaturesofthemost from 20%to40%. a Formational LandslideDensityIndex which ranges and “OlistostromadiCanossa”). All theseunitshave “Melange diBaiso,” “MelangediCostadeiBuoi,” belonging totheEpi-LigurianSequence(e.g. the sedimentarybreccias(EoceneandOligocene) Scabiazza,” “Argille Scagliose” Auctt.), aswell a Palombini,” “Argille Varicolori,” “Arenarie di Ligurian andSub-LigurianDomains(e.g.:“Argille largest number oflandslidesarethoseassignedtothe TLDI For theentireEmilia-RomagnaRegion, theaverage the areaofterritorialsurface considered. Municipality, Province, drainagebasin,etc.)and given territorialsurface-type classifi the sumoflandslideareaoccurringwithina • entire formationtaken intoconsideration. (over theEmilia-Romagnaregional territory)ofthe geological formationand the sumofalllandslideareasoccurringwithineach di Bismantova” nearCastelnuovo Monti). sub-vertical slopesandmesa-like features(i.e.“Pietra superimposed fl affected bybadlandsandlandslides,whereasthe a gentlegradient(usually10-20°)andareoften The slopescomposedofclayandchaoticunitshave Epi-Ligurian Sandstones(i.e.Bismantova Group). • different parameters(Bertolini Index (LDI), Emilia-Romagna isassignedbythe The variability oflandslidedistribution within features andcauses Landslide distribution, TLDI (Territorial LDI) FLDI (Formational LDI) value is17.1%. The rockunitsaffected bythe whichhasbeendeterminedbasedontwo ysches orsandstonescaneven present = = S s/St * s/S* is themappedsurface et Al. Landslide Density 2002): 100: where 100, where cto (e.g. cation 25-05-2004, 13:23:34 Argille St s s is is is LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Figure 3 - The fl atter, wider and apparently stable parts of the Apennine slopes where many villages grew up over the last few centuries often are the exposed feet of very large, dormant landslides. Photo by Giovanni Bertolini, September 2002.

scagliose (“scaly clay”) and Complesso caotico prevalently argillaceous materials is accompanied (“chaotic complex”). by physical weathering processes that often lead to In terms of their shear strength properties, these a consistency lower than the solid state; in this way materials show a high degree of variability, which their initial condition of “weak rock” is lost and they is diffi cult to quantify. This is particularly true assume the characteristics of a clayey soil aggregate. because progressive water absorption in these The minimum shear strength values are found in Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 4 - The layered structure of a typical landslide investigated by means of continuous-core borings. Sample age increases as depth increases. A well-preserved 2400-year old tree trunk was found inside the landslide. (original data by Giovanni Bertolini).

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini in fullyconfi affecting thematerialwhenmovement takes place fragments andasqueezingoftheclayfraction) to themechanicalaction(agrindingofcoarser shifted toward thefi body itself.Moreover, grain-sizeselectionwas clearly more) comparedtothebedrockandlandslide higher naturalmoisturecontent(atleast20to30% breaking pointsurface duringmovement revealed a Some testsanddirectfi (for example, argillaceous materials withmontmorilloniteminerals and lodgethesecondnightoffi off fromthe“Ligurian”oceanfl red ophiolitelyingwithintheChaoticComplexes oftheLigurianDomain.Itisa mass ofpillow lavaswhich was sheared Figure 5-TheRossenaCastle,oncethepropertyofCountessMatildediCanossa,islocateduponacliff composedof now beoutdated,owing tosubsequentevolution of a periodoftimerangingfrom1982to1995—may classifi classifi at thetimeofsurvey, theremainingoneswere six percentoflandslideswereclassifi scale, intheEmilia-Romagna Apennines. Twenty- production oftheRegional GeologicalMap,1:10.000 been identifi Approximately 32,300landslidebodieshave Features oflandslides cations—established bythesurveyors over ed as“dormant.” Obviously, someofthese ned conditions. ed duringsurveys carriedoutforthe Argille di Viano ner fraction:thisisobviously due eld observations madeonthe oor bytheLiguriannappeduringitstranslationalmovement. Herewe’ll have dinner ). eldtrip. PhotobyGiovanni Bertolini,September2003. ed as“active” (1993). These earth fl earth (1993). These may beclassifi with displacementvelocities whichinsomecases earth fl A liquidconsistency is reached,thusproducing break-up ofthemass,becomessaturatedwithwater. decline ofitsmechanicalpropertiesand,following sizes. The displacedmaterialundergoes arapid accompanied byslidesofrockmassesvarious reactivation causesaregression ofthemainscarp, are large rotationalslides inthesourcearea.Each When reactivation occurs,thefi translational slidesinthelower andfrontalparts. slides intheupperpart,andmultipleadvancing by multipleandretrogressive rotational-translational viewpoint, theselandslidesaregenerallycharacterised “widening” onbothfl upper part;“advancing” inthemid-lower part;and landslides” (WP/WLI,1993):“retrogressive” inthe landslides, they shouldbeconsideredas“reactivated As forthe classifi from slow torapid,accordingCruden& Varnes’s the landslide. The actual andtypicalvelocities vary cation. ows. These earthfl state ed as“rapid,” accordingto WP/WLI , distribution ows soonwidenasfar outas anks. Fromatime-sequence and ows move downward style ofactivity rt movements rst 25-05-2004, 13:23:38 of LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Figure 6 - Landslide distribution within the Emilian Apennines during the last 15,000 years. Legend: A - probable origin of landslides; B and C - reactivations. (original data by Giovanni Bertolini).

the landslide body’s mid-section, and may partially overlap the accumulation zone, thus forming wide, fl at fans with average slope inclinations of less than 10°. The accumulation of earth fl ows over the basal accumulation material may induce an undrained overload and, consequently, a sudden increase in porewater pressure, thus reactivating the whole landslide body, from head to toe. At least 1300 of the landslide bodies in Emilia- Romagna have an estimated volume exceeding one million cubic metres. Some landslide bodies have a total length exceeding 5 km: the largest ones are classifi ed within the most frequent complex type, that is, the slide-fl ow. From plan view, these landslides show a large crown (with slope inclinations >20°), a relatively narrower middle “channel” corresponding to the area of fl ow, and a wide basal fan with a modest slope inclination which is often <10° (example: the Morsiano Landslide represented on the cover of this booklet). The depth of the rupture surface is most frequently from 10 to 15 m; about 20% of landslides have a Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 7 - Reggio-Emilia Apennine: monthly distribution of landslide-triggering events in the 20th century (histogram “a”) vs a typical curve of rainfall (line “b”). This graph was drawn on the basis of the triggering dates (mostly reactivations) available for about 1000 landslides. Despite the time distribution of precipitation, landslides occurring in the spring are much more frequent than autumn ones. That demonstrates the importance of spring snowmelt as a triggering factor. (from Bertolini & Pellegrini, 2001).

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini Map (Bertolini (Pizziolo, 1996),andtheLandslideSusceptivity The new Inventory MapofLandslide Distribution The Risk mainly duringperiodsBandC. subsequent growth occurredin the following period, beginning ofthe Holocene(AinFigure6). Their litosomes originatedduringtheLate-glacialor previous landslides. As shown inFigure6,thepresent In fact, thelastglaciationerodedalmostall glacial andHolocenicclimate. 4). These landslide bodiesaretheproductofLate- superimposed, relatively minor, earthfl each large landslide body iscomprisedofseveral progressive) depths,thusdemonstratingthat (and progressive) agearefoundatdifferent (and useful forradiometricdating.Samplesofdifferent of wood remnants(buried bythelandslides) continuous coreboringsallows forthecollection carried outinrecentyears. The increasingusageof this isdemonstratedbyabout50radiocarbondatings earth fl landslide bodies,many ofwhichwereoriginally a completeorpartialreactivation ofpre-existing The majorityoflandslidesareconsideredtobe depth exceeding 20m(Figure8). b) classesofdepth(fromBertolini&Pellegrini, 2001). to 15m,whereasabout20%oflandslidesshow adepthexceeding20m.Legend:a)numberoflandslides; carried outonabout70inclinometercurves. As onecansee,thehighestfrequencyisfound for depthsrangingfrom10 Figure 8-Depth(inm)oftherupturesurfaceslandslidesinReggioEmiliaProvince. Thiscalculationwas ows fromseveral thousandsofyearsago; et al . 2002)producedbytheEmilia- os (Figure ows Emilia-Romagna isin10 lost becauseoflandslides. According tothisauthor, to 1990inEmilia-Romagna“just”47lives were negligible. Catenacci (1990)statesthatfrom1945 The riskofhumancasualtiesisrelatively low, yetnot creating risky situations forsomany settlements. events, have always favoured thischoice,thus of human“memory,” especiallyforlocalhistorical of several centuries)andthewell-known shortness landslides, reactivation timemaybeontheorder <10°). The low reactivation frequency (forlarge of theirfrontalandmid-accumulationzones(often settlement sinceancienttimes,thankstothelow slope landslides have beenareasdeemedsuitableforhuman development, rillerosion,creep,etc.).Large dormant is subjecttomany weatheringprocesses(badland is adirectresultofthe Apennine environment, which 1608 morebydormantlandslides. This large number upon, oraredirectlyaffected by, active landslides,with more buildings, excluding “scatteredhouses”)lie show that281inhabitedplaces(defi the statisticaloccurrenceoflandslides. These maps 25,000), arethemostusefuldocumentsforexamining a scaleof1:10,000andpublishedatthe1: Romagna Region (boththemapsweresurveyed at byslope instabilityinthatsameperiod. The relatively regions, inthesad classifi cation ofcasualties caused th placeamongsttheItalian ned asfouror 25-05-2004, 13:23:46 LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Figure 9 - The number of landslide reactivations per hydrological year is here compared to the cumulative rainfalls and snowfalls. The dates of events are from Brunamonte (1999), who recorded over 1000 pieces of data, taken from historical documents in the archives of the province of Reggio Emilia. Since the pluviometric regime shows here two main peaks (October and November) and a minimum in July, all data are grouped per hydrological year (from August to August). The number of landslides occurring during the fi rst half of the century is slightly underestimated, because of different laws and loss of data. The hydrological year 1959-60 was the most rainy and with the greatest number of landslides in the century. This graph is useful for establishing the triggering causes as well. In fact, one can see that normally there is a good correlation between events and rainfalls. Instead, when the landslide maximums do not agree with rainfall peaks (e.g. 1963-64 and 1986-87), they correspond to the snowfall peaks. 1963-64 was the second landslide apex of the century, but was caused mainly by snowmelt waters (from Bertolini & Pellegrini, 2001).

low number of lives lost in this region is due to the bodies, and so is threatened, as well as periodically DO1 to P13 n° 3 - from Volume generally slow displacement velocity of landslides. affected, by slope movements. Unlike bodily harm, social and economic damage is Sometimes, owing to the uplift of the landslide extremely diffi cult to quantify, however the amount foot (in the case of landslides with a rotational- is noteworthy. All the mountainous areas of Emilia- translational rupture surface) and/or complete Romagna are, in fact, affected by the presence of obstruction of the valley fl oor (simple earth fl ow), landslides, causing a consequent progressive human a dammed impoundment is formed. In this case, migration out of the rural areas. A good 16% of the hydrodynamic risk related to the possible collapse of total road network is on top of existing landslide the damming materials is very high. In recent times,

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini landslides, Among the landslide bodies. the claymaterialsthatmake upmostoftheslopesand turn, totheextremely low hydraulicconductivity of is certainlycausedbyvery slow percolationdue,in of movement. The slow recharge ofgroundwater of water saturationsuffi necessary formostlandslidebodiestoreachastate Obviously, thisphaseshiftcorrespondstothetime precipitation peakandthecorrelative landslidepeak. the delayofoneortwo monthsbetweentheautumn The samegraphinFigure7alsoclearlypinpoints snowmelt water iscombinedwiththespringrainfall. the Apennines untillatespring. Thus theactionof snow cover maylastatthehighestelevations in this mustberelatedtosnowmelt, sinceextensive occurring inspring(disproportionatetorainfall); The graphhighlightsthegreaternumberoflandslides autumn one). rainfall peak(onaverage slightlylower thanthe absolute value) actuallyaccompaniesthesecond spring landslideevents (April,whichishigherin peak rainfall (October),whereasthemaximumin events (December)occursoneortwo monthsafter shows thatthemaximumofautumn-winterlandslide only 29%betweenOctoberandDecember. Figure7 events occurredbetweenMarchandMay, whereas Emilia Province wefi occurring over thepastseveral centuriesintheReggio investigations ofthemorethan1000landslides monthly distribution ofmasswasting events. From in causinglandslidesisdemonstratedbythe On theotherhand,importanceofsnowmelt the reactivation oflarge landslides. possible tocorrelatelong-lastingprecipitationwith a majorroleintriggeringmasswasting. Itisusually such as structurally complex materials rocks, whichareclassifi weak sedimentary, sensitive andintenselytectonised formations outcroppingare,infact, composedof related to in themountainsofEmilia-Romagnaisprimarily The extremely highnumberoflandslidesoccurring Causes impoundments exceeded onemillioncubicmetres. In abouthalfoftheknown cases,thesizeof sudden, uncontrolledcollapseoftheimpoundment. size —areartifi these impoundments—sometimesofconsiderable intense and/orprolonged precipitation geological causes earthquakes triggering causes cially drainedinordertoavoid a nd that48%ofthemasswasting shouldnotbeforgotten, even cient toinitiateresumption e as ed . Nearlyallthegeological oftheEmilian Apennine . Also lithologically and/or physical causes play

history ( time” whichcanbeestablishedlookingatthepast be quantitatively describedbytheevent’s “return landslide body. The probabilityofoccurrencemay time, representquantitatively the“hazard”ofeach The repetitiveness ofreactivations, andtheirreturn Occurrence andrecurrence oflandslides. degree MCSintensity. (Reggio EmiliaandModenaProvinces) withan8 in September1920,whichstrucktheupper Apennines earthquakes, like theseismicshock(6.5magnitude) seismic caseswerecausedbyparticularlystrong with certainty. Inthisregion thosefew, defi though seismictriggershave seldombeenidentifi Apennine mountainridgenearPasso dellaFutaat Coming fromFlorence,thehighway crossesthe local roadstoMonteBeni. We leave thehighway atRoncobilaccioandgoalong Beni (Stop1.1). description Itinerary A monitoring Radar Synthetic Aperture cartography, GPS,ground-andsatellite-based Topics oftheday: 1.2), andstateroad(S.S.64)ontoBologna. roads toMontovolo (Stop1.1),RoccaPitigliana Via the A1 highway toPiandel Voglio andthenlocal Florence -Bologna itinerary Field tripitinerary snow packinearlyspringtime. landslide triggeringcauseisclearlythemeltingof (e.g. hydrologicalyears1963-64and1986-87)the the snow graphinFigure9shows thatinsomeyears throughout theoverall trend. According toFigure7, time, althoughsometen-yearfl data show adecreasingtrenddown tilthepresent the 1960-1961hydrologicalyear. Afterwards, the shows thatthemaximunofactivity was reachedin trend (Figure9). The numberoflandslidesperyear by hydrologicalyears enabled ustocomparethelandslidehistory, grouped 20th centuryhave beencollected). This researchalso (records ofover 1000landslidesoccurringover the of the Apennines oftheReggio EmiliaProvince analysis ofarchival documents,asshown by research Landslide hazardmaybegarneredfromahistorical “historic failure rate” Apennine geology, landslide , DAY 1 with therainfall andsnowfall –fromFirenzetoMonte uctuationsareevident in W U

et Alii 25-05-2004, 13:23:57 , 1996). nitely ed LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

about 900 m a.s.l.. Here we are close to the “Sillaro instability problems associated with the fall of blocks line” that runs straight towards the NE and divides of several cubic metres in size. However, for the fi rst the “Ligurid” nappe of the Emilian Apennines from time, it also recognised the presence of a mass of the harder sandstones of the Marnoso-Arenacea heavily jointed rock in precarious stability conditions, fl ysch, Miocene in age, which outcrop extensively in located at the upper part of the mountain. the Romagna Apennines. Once on the Emilian side In April 2002 after a moderate rainstorm (66.4 mm of the Sillaro line, following along our journey, the of rain between the 12th and the 13th of April), new Marnoso-Arenacea forms the deep substratum of the dramatic evidence of instability appeared on the Ligurian Nappe and does not outcrop, except forthe slope. tectonic window of Salsomaggiore near the Parma After a fi eld survey it was possible to assess the actual Apennine border. size of the problem: the upper boundary and the right The highway tunnels take us through a ridge fl ank of the rockslide were clearly defi ned by an composed of foredeep clastic turbidites of the opened perimetral crack, 320 m long. Macigno Formation (Late Oligocene to Aquitanian In a case like this it is very important to assess in age) that conclude the Tuscan Nappe Sequence. the volume of the incipient rockslide rapidly and In this area the Macigno is composed of alternating precisely, because volume is one of the main factors well-cemented sandstones and pelites, and shows its controlling the runout in the case of a catastrophic large-scale NE verging fold-and-thrust structure. We failure and, therefore, the consequences in terms of are now entering into the Po Plain side of Apennines expected loss. In particular the value of 1 million m3 where, during the journey, we can see several seems to be the limit between low mobility and high splendid views. They all present ideal opportunities mobility rock avalanches. to describe the geological structure of the Apennines For this reason it was decided to employ LISA, a new and visualise the complicated relationships amongst remote sensing technique based on SAR (Synthetic the different domains and units. Aperture Radar) interferometry, developed at the Joint Research Centre (JRC) of the European Commission, Stop 1.1: specifi cally for the fi eld assessment of ground surface Monte Beni displacements (Figure 10). This novel system was by Nicola Casagli, University of Florence used at Monte Beni in a monitoring campaign lasting Monte Beni (elevation 1260.5 m a.s.l.) is located 2 weeks, from the 5th to the 19th of May 2002. in Northern Tuscany (Italy), about 8 km NW of The basic principles behind the system involve the Firenzuola, a town well-known for the industrial SAR interferometric technique developed over the production of quarried stones. last decades in the realm of satellite imaging. The eastern slope of Monte Beni was worked over by This system must be installed in a stable position quarrying activity, to produce construction material, in front of the area to be monitored, which must be from an ophilolitic sequence, which lies reversed over completely visible from this position. Cretaceous clay-shales pertaining to the Ligurian The entire operational chain of data processing nappe. The sequence is composed, from the top to the can be done directly in the fi eld using portable bottom, of the following units: instrumentation and a laptop PC, thus providing real- a) massive jointed basalts; time information. b) basalts with a pillow-lava structure; The fi nal product is a sequence of interferograms c) basalt breccias; showing, pixel by pixel, the phase differences d) a thin layer of laminated cherts (Diaspri between successive images. Formation); Interferograms, after the transformation of phase e) limestones with marl inter-beds (Calcari a values into displacement, come up with direct, DO1 to P13 n° 3 - from Volume Calpionelle Formation) with a regular bedding multitemporal deformation maps showing the fi eld of dipping into the slope. displacements along the sight-line of the system over The lower part of the mountain chain is covered by all the area where the radar backscattering is coherent slope-waste deposits with visible remains of ancient enough (corresponding to the less vegetated sectors rockslides. of the slope). A geological study, commissioned by the Firenzuola The atmospheric conditions during the monitoring of Municipality for the recovery of the quarry area, Monte Beni were quite troublesome since for most fi nished in July 2000, confi rmed the well-known of the time the slope was covered by dense fog. In

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini Monte Benirepresentsthefi maximum depthoftheslidingsurface isabout30m. ) LISAcanbeusedformonitoringmovements a) points arose: From thisfi supported byCivil Protectionauthorities. operational conditions,onthebasisofadecision new SARtechnologyofLISAwas appliedinreal initial estimateof1 effective magnitudeoftherockslide,confi After theLISAprojectitwas possibletoassessthe and time. mass andtheevolution ofthemovement over space with highprecision,theboundariesofmoving rockslide mechanismandhasallowed ustodelimit, The dataprovided bytheLISAclearlydefi were fullycarriedout. topographic systems,whereastheradarobservations these conditionsitwas notpossibletouseany optical raw dataatselectedpositionsalongtherail..PhotobyNicolaCasagli, 2003. receiving antenna,which slidesalongastraightrail,about3mlong.Thesyntheticapertureisrealisedbyacquiring Figure 10-LISAisaground-basedportableapparatus consistingofamotorisedsled,carryingtransmittingand requires onlyafew hoursanditisabletoprovide during anemergency sinceitsinstallation rst operationaltestthefollowing positive × 10 6 m 3 ofmaterialinvolved. The rst caseinwhichthe rming the rming nd the ned Voglio exit, we’ll take municipalandprovincial roads a chaoticstructure.Furtheron,afterthePiandel calcareous turbidites(CanetoloComplex), with consisting ofPaleocene-Middle Eoceneshaly- through theSub-LigurianSestola-Vidiciatico Unit, Castiglion deiPepolianticline,thehighway proceeds Once weleave theMacignoFormation ofthe Montovolo. Voglio, thengoalonglocalroadstoCamugnanoand We take thehighway northward andexit atPiandel 1.1) toMontovolo (Stop1.2). Itinerary Bdescription LISAremotelyassessesdisplacements,without d) LISAdelivers multitemporalinformationat c) LISAiscapableofassessingtheentire b) needing toaccesstheunstablearea. short timeintervals (10minutes); in zoneswithscarceormoderatevegetation; deformation fi real-time data; eld ofamassmovement, atleast – fromMonteBeni(Stop 25-05-2004, 13:23:59 LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

that will head NW across the Sub-Ligurian Units Cretaceous Argille a Palombini and then through to Castiglion dei Pepoli, and farther on, across the the Miocene sandstone of the Bismantova Group. Ligurian nappe, to Montovolo where the fi rst stop is Stop 1.2 is located close to the sedimentary border planned. between these units. The church of Rocca Pitigliana stands upon a small cliff composed of well-exposed Stop 1.2: Miocene sandstones. Montovolo. The Montovolo and Monte Vigese cliffs (approximately Stop 1.3: 1000 m a.s.l.) are composed of Miocene sandstones The Rocca Pitigliana monitoring system. belonging to the Epi-Ligurian Bismantova Group. By: Matteo Berti, Monica Ghirotti, Alessandro They are calcarenites and calcirudites deposited in a Simoni, and Paolo Baldi (University of Bologna). shallow marine environment (continental platform), highly fractured by systematic joints and mesoscopic This recurrent landslide represents a small but faults. The two cliffs stand on the clayey units of the fruitful fi eld test of several ground-based monitoring Ligurian Nappe and provide one of the best views of techniques: GPS, pore pressures, and inSAR. the Bologna Apennines. On one cliff stands a small This mudfl ow, rapid to moderate in speed, originates one-thousand-year-old monastery. The large Lissano on a slope made up of the Cretaceous “Argille a landslide lies at the foot of the slope and is almost Palombini” Formation. It is a unit pertaining to the completely visible. This is a very ancient earthfl ow Ligurian Domain, with block-in-matrix structure, showing all the typical features of a landslide: it is a made up of a grey clay-shale matrix, including blocks few kilometres long, several hundreds of meters wide of limestone and sandstone. The features of the unit is and it has the typical hourglass shape with the large clearly shown in the crown of this little landslide. and fl at toe lapped by the watercourse. After each Long-term automatic monitoring has proved to be reactivation, its lateral convexity effectively channels effective in answering some of the most compelling rillwash towards the landslide’s fl anks, forming questions: two streams that erode these fl anks, thus creating • what is the relationship between rainfall and the characteristic shape. The toe extends onto the landslide movement? main valley fl oor, creating somewhat of a meander • how do groundwater pressures respond to in the river, often damming the valley and causing transient rainfall? the temporary formation of a lake. The existence of • does rainfall infl uence groundwater only by a third stream that cuts the landslide body, running modulating a steady or quasi-steady water table parallel to the fl anks, suggests possibly two different (slope-parallel fl ow) or by transient infi ltration yet now coalesced landslide bodies. of water (vertical fl ow)? At this moment this landslide is considered dormant. • which is the most effective drainage system? Several hamlets and scattered houses have been • were the preventive works successful? built upon it during the last century; for this reason A good understanding of the subsurface fl ow fi eld it represents an example of a local population would reveal rainfall effects on the timing and style of unknowingly accepting a hazardous condition. landslides, and it would hone model forecasting and countermeasure design. A brief presentation about landslide cartography and The aim of the monitoring system is to detect the the use of satellite-based earth observation techniques subsurface fl ow fi eld in the headscarp area and to (InSAR) will be held by the geologists of the Regional correlate landslide movements to rainfall events. The Geological Survey, utilizing computer projections. system consists of: • 16 pore pressure sensors DO1 to P13 n° 3 - from Volume Lunch is planned in the fi eld in Montovolo. We will • 3 soil moisture sensors (electrical capacitance) have grilled meat and typical dishes catered by a local • 3 tensiometers restaurant. • 1 rain gauge • 1 surface wire extensometer Itinerary C description – From Montovolo (Stop Data is recorded every 15 minutes and downloaded 1.2) to Rocca Pitigliana (Stop 1.3): via GSM every 15 days. This short excursion runs across the Ligurian Nappe and Epi-Ligurian Units: we will cross through the Sensor recordings

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini accuracy oftheothermethodologies adopted. shape obtainedfromotherssurveys, andtocheckthe to performadirectcomparisonwiththelandslide’s Subsequently, itwas reducedtoa1x1mgridinorder high densityDEMsaccuratedown toa few centimers. resolution was upto5mm:processingresultedin performed byLaserScanning.Measurement Moreover, inthe headscarparea,asurvey was generated DEMs. permits directcomparisonsofthesuccessively measured withGPSinthesamereferenceframe from 0.5to1m. The useof22groundcontrolpoints enabled ustoobtaininternalDEMaccuracy ranging DEMs oftheareawereobtained.thisconfi and 1993images)two 1x1mregular- spacedgrid photogrammetric surveys wereperformed (the1976 For theRoccaPitiglianasitetwo aereo- DTMs obtainedfromGPSwillbecompared. gives ahighresolutionDTMtowhichthesubsequent provided bythedigitalphotogrammetricsurvey: it 1- The initial“zero” situationofthelandslideareais observations respectively. to afew centimetresforstaticandkinematic GPS measurementsrangesfromseveral millimetres Pitigliana landslide. The accuracy achieved withthese fast-static andkinematic)wereappliedtotheRocca photogrammetry anddifferent GPStechniques(static, Beside wireextensometers, acombinationofdigital Movement detectionandtopographicsurveys delayed andlesssharp. decrease; deepersensorresponsestendedtobe of rainfall), withasharpriseandthensmoother (an approximately10-hour-delay fromtheonset storm. Shallow sensorstendedtorespondquickly to avalue generallygreaterthanthatbeforethe sizeable pressureincreasesfollowed byadrop Following eachindividual storm,sensorsrecorded • • month ofdatamaybesummarisedasfollows: The generalpicturethathasemerged fromthefi from above ratherthanbyslope-parallelfl deeper portionsarerecharged bypercolation sensors thanindeepsensors,indicatingthat Hydraulic headstendtobehigherinshallow depth. episodes donotgeneratepressurepulsesatany shallow sensorsaredryandsinglerainfall and relatively quick.Duringsummermonths, single rainfalls atshallow depthsaresynchronous surface inthewetseason,whenresponsesto Saturation extends very closetotheground guration ow. rst downloaded fromtheremote receivers viaGSM sampled at10secondintervals, areautomatically Continuous dataobservations fromthetwo stations, on apillarbuilt attheheadoflandslidearea. outcrop outsidethelandslide,andotherone stations: thereferencestationissetuponarock movement isprovided bytwo permanentGPS 3- Finally, continuousobservation oflandslide (about 160000m2)in12hoursoperatingtime. positions werecollectedonthewholelandslidearea the landslideperimeter. Morethan40,000coordinate density ofabout1pointpersquaremetre,andtodefi planned soastocover thewholeactive area,witha at asamplingrateof1persecond. The pathswere walking alongthelandsliderecordingGPSsignal The moving GPSreceiver was carriedbyanoperator performed toobtainaDEMofthelandslidesurface. obtained. InMarch2003akinematicsurvey was of materialinvolved inlandslidemovement canbe the elevation values ofsuccessive DEMs,thevolume of irregularly distributed points. Then, bycomparing surface (a1x1metregrid)bymeasuringthepositions the kinematictechniqueprovides modelsofthe although withreducedprecision(somecentimeters). the positionofmany pointsinashortertimeperiod, with amoving receiver; itispossibletodetermine 3- Kinematicmethodsallow fordataacquisition topographical variations alongselectedprofi kinematic techniquesand,ifperiodicallyrepeated, provide bothaccuratetime-seriescoordinatesfor along thelongitudinalaxes ofthelandslide:these of minutesonseveral marked pointsdistributed static surveying, observations aremadeforaperiod precision, oftheorderafew centimeters.Inrapid infl while thealtimetriccomponentsmaybestrongly is sub-centimetrefortheplanimetriccoordinates, observable GPSsisapplied. The achievable accuracy sophisticated post-processingmethodusingallthe fi kilometres (rapidstaticmethod),aslongatleast about 10minutesforbaselinesshorterthanafew on network characteristicsandmaybereducedto possible precision.Staticoccupationtimesdepend the measurementsessionandproducehighest require GPSreceivers tobestationarythroughout movement throughtime.Staticsurveying methods to determinethelocationofapoint,aswellits 2- GPSsurveys areeffi ve GPSsatellitesperperiodarevisibleanda uenced bytroposphericconditions,giving lower cient andaprecisemeans les. 25-05-2004, 13:24:04 ne LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

to a server in our Local Area Network. Three-hour From Sasso Marconi (birthplace of Guglielmo sessions are automatically run through once a day. Marconi, the famous scientist and inventor of the The increase in the baseline length between the two telegraph), the highway will bring us to the city of permanent GPS stations gives information about Bologna, passing through the intra-Apennine Pliocene the velocity of the monitored point. The achievable clays and sandstones (observe the high cliff on the precision is the same as automated geodetic stations, left, just in front of the highway entrance) and then but with a lower temporal resolution. through Ligurian and Epi-Ligurian Units. Bologna is situated upon the Po Plain, yet very close to the Itinerary D description – From Rocca Pitigliana Apennine’s margin. The city’s southern edge and the (Stop 1.3) to Bologna. St. Luca Abbey (which rises on the last hill, and can The journey follows the national “Porrettana” road be seen to the right of the highway as we approach (S.S. 64) that runs along the Reno valley. At fi rst we the town) lie upon the Epi-Ligurian sandstones of the will encounter Chaotic Complexes of the Ligurian Bismantova Group. The southern part of the city lies Nappe. Beyond the village of Vergato, the steep and upon Calabrian sandstones, the western part upon overhanging cliff of Calvenzano marks the southern coarse-grained Holocene deposits of the Reno River limit of the superimposed slabs composed of Epi- fan. The remainder is set on the clayey and sandy Ligurian Miocene sandstones of the Bismantova overbank deposits of the Reno and Savena rivers. Group. Thick layers of calcirudites are evident, as In the city we will have a few hours to rest, and an well as their sub-parallel and horizontal attitude. optional tour, followed by dinner. The high cliffs (Monte Sole, on the right), consisting of the Epi-Ligurian Sequence, are evident on both DAY 2 sides of the valley from Calvenzano to Marzabotto, Bologna-Canossa itinerary and as far as the merging of the Reno and Setta Rivers. Some outcrops of clayey marls belonging to Along the A1 motorway to Modena and then on local the Antognola Formation (Upper Oligocene-Lower roads to , Cerredolo and Cavola (Stop 2.1). Miocene) are evident near “Pian di Venola” (on the From there we’ll continue the trip to Poviglio (Stop left), whereas the Reno River fl ows directly over 2.2) by helicopter. We’ll fl y over the impressive Bismantova sandstone outcrops (on the right). landslides of Morsiano, Valoria, Roncovetro and others. From there we’ll go by bus to the well-preserved medieval Rossena Castle, historically the property of Matilde, Countess of Canossa. In the castle, built on rough and steep ophiolites, we will have dinner and also lodge

Topics of the day: the risk-management of villages founded on large landslides, monitoring methods, and relocation of villages.

Itinerary E description – From Bologna to Cavola (Stop 2.1):

From Bologna to highway A1 DO1 to P13 n° 3 - from Volume (“Autostrada del Sole”), we will come to Modena, and then take regional and provincial roads to Sassuolo and Figure 11 - The ruins of Matilde di Canossa’s castle, rising on a thick Morsiano. stratum of miocenic arenites pertaining to the Bismantova Group. The castle was one of the main centres of power in the Middle Ages, during The fi rst part of the journey will be quick the War of Investitures. Here, in 1077, the German Emperor Henry IV, as we cross the Po Plain. Past Sassuolo, barefoot, kneeled before and begged Pope Gregory VII to repeal his we will follow the Secchia River Valley excommunication. Aerial photo by Giovanni Bertolini, September 2003. and enter into the Apennine hills,

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini over, whichafterwards was artifi been considerablydisrupted:a15mhighstepwas left the watercourse’s profi of theimpoundmentover sixmonths.Sincethen, by the stabilisation measuresadoptedsoonaftertheevent blockage inordertomake anaturaldam.However, time, therewas discussionaboutreinforcingthe layer. 13,000,000m detached andslidalongadownstream dipping A large block ofHelmintoidfl merits description. we donotplanastopattheLupazzolandslide,itstill moved rapidlyon April 23,1960(Figure12). While body oftheLupazzolandslide,now inactive, which Past Cerredoloandvisibleontheleft,islarge Panoramic view I Flysch adElminntoidi,etc.). Palombini, ArgilleVaricolori,Scabiazza, di Arenarie Clays” andsands),thenLigurianunits(Argille a crossing throughmarinePliocenesediments(“Blue of calcareousfl Figure 12-Thisphotowas taken immediatelyafterthedetachment of thelargerock block m Cerredolo lake (maximumimpoundment26,000,000 dammed thevalley fl This lake lasted8monthsbefore itwas drained.PhotobyE.Carra,Parma, 1960. 3 over asurface ofabout2,000,000m Genio Civile ysch which dammedthevalleyfl : The Lupazzo landslide Lupazzo : The ledtotheregulated drainage 3 ofmaterialaccumulatedand le andhydraulicregime have oor, formingthetemporary cially stabilisedby ysch anddebris 2 oor andformed Lake Cerredolo. ). At that ). At Cerredolo Lake depositedsome1millionm means ofthreesuccessive dams.Duringitslifespan, the villagehasincreasedthreefoldinrecentdecades, body’s ridge,whichis4kmlong. The territoryof village ofCavola liesdirectlyuponthelandslide tolerate theriskassociatedwithlandslides. The large impressive examples ofhow peoplecan implicitly 13). The large Cavola landslideisoneofthemost River abuts thetoesofthreelarge landslides(Figure Beyond Colombaia, therightbankofSecchia Cavola, aSub-Boreal landslide. Stop 2.1: complexes, whilethevalley fl slopes onbothsidesarecomposedofLigurian which follows alongthevalley fl We passtheLupazzolandslideonaprovincial road on CerredoloLake. fi passage ofthecoarsermaterials.Itisstillpossibleto wide valley fl and silt,onlypartiallyerodedbytheriver. The present be madetoseetheselacustrinedeposits. 1960 byCerredoloLake. Ifpossible,abriefstopwill gravel buried byclayandsiltrapidlydepositedin nd oldpostcardsrepresentingsmilingpeoplerowing oor sillhindersalmostcompletelythe oor isconsists offl or Te valley The oor. 3 25-05-2004, 13:24:07 ofclay uvial LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

in spite of several local reactivation events which by the advances of the Fernau and Forni Glaciers in occurred before 1960, as well as several recent local the Alps. reactivation events occurring near the landslide’s In historical times, the oldest record dates to 1100- perimeter. The apparently inactive main body of 1600 A.D., when the “old” church was “destroyed the landslide is moving slowly (a few mm/year) at by a landslide” and a “new one”, which still exists a depth of 45 m., as demonstrated by inclinometer today, was built. The most recent failure of a large monitoring. portion of the landslide body was in 1960, when a mudslide-mudfl ow descended from the crown to the Depth Lab.code yr.BP Cal.yr present position of the village of Cavola,, destroying (m) BP(2σ) the hamlet of Morra and several scattered houses. -9 Beta 2970±40 3255-2990 Total displacements of several hundreds of metres 135395 -24 Beta 3250±40 3895-3690 were observed. The landslide body of the 1960 event 135394 is presently covered by vegetation and agricultural -32 Beta 3720±40 4160-3690 fi elds. People, completely unaware of the landslide’s 137039 -37 Beta 3660±40 4070-4035 recent past, again want to build upon the landslide. 137040 4000-3700 We are going to Cavola’s football ground where we’ll -45 Beta 3600±70 4090-3700 have our lunch. From there we’ll take off by helicopter 135396 for a panoramic fl ight through the Secchia and Enza Valleys. The next destination: the Poviglio landslide. Table 1 - Radiocarbon dates on wood fragments found During the fl ight we will see several landslides. within the Cavola landslide. The most interesting ones are the Morsiano and the “Lavina di Roncovetro” landslides. Obviously, there The 60-m-long continuous core, bored through the will be no time for in-fl ight conferences, so the case- landslide body in 1997, is available and has been histories will be discussed on the ground before the described. The landslide is mainly nourished by fl ight. Ranzano Sandstones (Oligocene) that form the left side of the valley in which the landslide is lying. Panoramic view II: The late-glacial Morsiano The right side is formed by Helmintoid Flysch. The landslide. vertical fault between them is directed N-S and buried by the landslide. The high clay content determines The oldest landslide dated in the Reggio Emilia- the mechanical behaviour of the descending mass. Province is the Morsiano. It is also the most well- This landslide is one of the most investigated in terms defi ned with a clear hourglass shape (photo on the of its evolution through time. Several wood samples cover). Total length is 4 km. The estimated volume were collected at different depths and allow the is more than 100*106 m3. The river abuts and reconstruction of the landslide’s evolution, starting erodes the landslide’s toe, thus revealing several well- from the lowest sample (45 m, near the base of the preserved tree trunks (Figure 14) which were once landslide) that dates back to 4090-3700 years before buried by the mudslides and mudfl ows descending present (95% probability, calibrated according to from the cliff of Mt. Penna. The slope’s bedrock is Stuiver’s curve). Younger remnants were found at composed of Hepiligurian fl ysch, Cretaceous in age. lesser depths, as shown in Table 1. The oldest trunk dates to before the Holocene (Table 2). The ages are chronologically in order from the Depth Lab.code yr.BP Cal.yr youngest (on the surface) to the oldest (at the (m) BP(2σ) landslide’s base) and testify to the layered internal -10 Beta 11390±70 13790- Volume n° 3 - from DO1 to P13 n° 3 - from Volume structure of the litosome. The landslide is actually 125333 13670 formed by the superimposition of several minor 13500- mudslides over a time span of approximately 1000 13145 0 Beta 3720±60 4240-3900 years during the Sub-Boreal period. More precisely, 166926 the landslide’s growth corresponds to the so-called “Lobben oscillation” (Veggiani, 1986) or “notable Table 2 - Radiocarbon dates on wood fragments found cold episode” described by Rothlisberger (1986), within the Morsiano landslide. when the climate was cold and wet, as demonstrated

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini 12,000 and6,000cal.yr. B.P. byGeraga on theMediterraneanseafl an increaseof100%inrainfall. The Sapropellayer testifi sudden increaseofmethane(40%)intheatmosphere the temperaturebecamequitesimilartopresent. A increase of7-8°Coccurredat14,700cal.yr. agoand yr. B.P.). After theLastGlacialMaximum,arapid warmer andwetterHoloceneperiod(11,800cal. (18,000-20,000 yr. B.P.) andthebeginning ofthe Glacial period,betweentheLastMaximum The landslideoriginatedduringtheso-calledLate- an earthfl recent reactivation occurredinautumn2000,andwas on theoppositesideofDoloRiver. The most Mt. Modinoandextends down tothevalley bottom The active Valoria landslide liesbelow thesummitof Panoramic view III: recent movement. as “dormant”sinceonlysmallportionshave shown the slidingsurface. The entirelandslideisclassifi maintain theshearstrengthatresidualvalues along not evident onthesurface, but aresuffi These smalldisplacements(2cmin4years)are landslide atadepthof25meters. slope andareoccurringnow inthemainbodyof slow, smallmovements whichare directeddown where thelandslideisseeminglyinactive, indicates even today. An inclinometrictube,excavated from Other partialreactivations dateto1880,1959and The new churchbuilt shortlybefore1725stillexists. to before1300,was destroyed by“thelandslide.” Between 1700and1725,theoldchurch,whichdated of landslideevents, datesbackto1631and1651. for Morsiano,existing intheregional data-base last few centuriesanddecades. The oldestrecords of ithave beenrepeatedlyreactivated even inthe Varnes’s sensu)despiteitsoldage.Several sections cannot beconsideredas“relict”(Crudenand As withtheCavola landslide,theMorsianolandslide Younger trunkswerealsodated. Some have adiameterofover one-halfmeter. Tree trunksoutcroponbothbanksofthewatercourse. like conditionsuntilthebeginning oftheHolocene. Younger Dryaswhichbroughtaboutglacialperiod- to 13,000cal.yrB.P., occurringshortlybeforethe Allerød coldfl More precisely, thislandslideoriginatedduringthe released bymeltingglaciers. is anothercluethatlarge amountsoffreshwater were es tothedevelopment oflarge wetareas,with ow. The landslide’s lengthisalmost4km, uctuation thatlastedfrom14,000 the Valoria landslide. oor, datedbetweencirca et al cet to cient . (2000), ed

The totalvolume ofthelandslideisabout3 1993 andisoccurringeven today. collapse ofbothlithosomestogetheroccurredafter lithosome hashadfrequentreactivations. Total been dormantsinceatleast1936,whiletheupper showing an“ lower lithosomeisolderandmorecompact,currently had beenstablearenow enteringtheslidezone. The as anew formation(regressive), sincesoilswhich from thecrown, thismayessentiallybeconsidered continually replenishedbyclayandwater entering 1 kmlongandalmost20mthick. The upperpartis 1.5 kmlongand10mthick,whilethelower partis by several ancientmudfl superimposed uponathicker lithosome(L2),formed velocities ofupto10m/day. The upperportion(L1)is very-active fl the landslidetobehave initsupperportionasa dominant fromthemechanicalpoint-of-view, causing calcareous-arenaceous fl 15). Mt.Staffola iscomposedofSub-Ligurianclayey where itcausestheformationofasmalllake (Figure the topofMt.Staffola down tothe Tassobbio River, We areintheEnza Valley. The landslideextends from Panoramic view IV reality. To date,thethreatofriver damminghasnotbecome via GSM. the landslide’s foot. All thedataaretransmitteddaily within thewatercourse andaweb-camfocussedon set-up. Itiscomposedoffourwater-level gaugesset in thedam,amonitoringsystemwas immediately risk ofdownstream fl river atthefootofslope.Inordertoavoid the risk was thethreatofalarge rock massdammingthe evident fromthemorphology. The majorresultant originated withinalarger landslidebody, clearly clayey Ligurianchaoticcomplexes. The 2000event is composedofhelmintoidfl caused byhighporewater pressuresmaintained by lithosome isremarkable:thepermanentfl evidentfl zone. The that linksthedepletionzoneandaccumulation 30 to40mwideanddeeplycarved intothebedrock, year. A uniquefeatureisthelongandnarrow channel, year, whilethelower onemoves afew decametresper the upperlithosomeisonorderofhectometresper has never completelystopped. The average speedof It hassinceslowed, duringthesummermonths,but The landslidereactivated completelyinautumn1993. and itsvolume is 8-10 udvsos mudfl uid-viscous en masse : the“Lavina diRoncovetro”. uidity thatcharacterisestheupper ooding duetoapossiblebreak *10 ” slidingmovement: ithad ows. The upperlithosomeis ysch. The clayfractionis 6 ysch (theupperpart)and m 3 . The slope’s. The bedrock ow, withmaximum uid stateis *10 25-05-2004, 13:24:13 6 m 3 . LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Figure 13 - The Cavola (foreground) and other dormant landslides lying on the right side of the Secchia valley. Photo by Giovanni Bertolini, September 2002. Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 14 - These tree trunks outcrop at the tip of the Morsiano Landslide. They date to the Late Glacial period (circa 13.500 cal.yr BP). The landslide’s clay matrix allows optimum preservation of the wood that appears fresh despite its age. Photo by Giovanni Bertolini, August 2003.

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highly-mineralised groundwater, mixed with methane, urban management. The longer the dormancy period rising from the deep subsoil. This phenomenon is (as with Cavola and Morsiano), the more people will evident in the graph in Figure 16, which presents build edifi ces and structures upon the landslide body. a daily record of water table depth (with respect to If landslide reactivation occurs more frequently (the ground level). The open pipe piezometer is situated Roncovetro example), the more people will be aware on the slope crest and the water table is found at the of the danger and therefore avoid building. unusually shallow depth of only 1.0-4.5m. The graph In conclusion, from the point-of-view of territorial shows sudden water-level rises of several metres, management, our main problem lies in those which cannot be directly related to the amount of landslides which show lower failure rates. The large precipitation (Bertolini & Gorgoni, 2001). Methane Corniglio landslide (which we will see tomorrow) is lowers the groundwater’s density and facilitates its the most obvious example: it was deceptively safe upward percolation. The state of fl uidity varies over until complete reactivation in 1994, after nearly a time and space, causing varying fl ow velocities inside century of dormancy. the moving mass. Because of this, the narrow median channel is often completely empty and the two Stop 2.2: lithosomes appear clearly separated. The extreme Poviglio solution: relocating the village. Discussion: Are we sure that an active landslide is This small landslide reactivated in autumn 2000 after more “dangerous” than a dormant one? heavy rainfalls. The triggering factor was a total of Cavola and Morsiano, as well as many others, 500 mm of precipitation, which is 25% of the annual demonstrate that landslides lying upon the region’s slopes are products of previous periods when the climate deteriorated. In the present climate, landslide activity is mostly due to recurrent “pulses” of existing landslide bodies, alternating with relatively longer dormant periods. From this perspective, the upper part of the Roncovetro landslide is an exception, as it is related to a peculiar pattern of groundwater replenishment. More commonly reactivation occurs with a slow earth slide which is caused by the intrinsic instability of a more ancient landslide body. The comparison amongst these landslides points out the main problems: anthropic factors and

Figure 15 - Plan view of the “Lavina

Volume n° 3 - from DO1 to P13 n° 3 - from Volume di Roncovetro” landslide, showing the location of the two lithosomes (L1 is the higher and more active block, L2 is the lower and less active block). The measured seismic velocity (P waves) is approximately 0.80 km/s in L1 and 1.2 km/s in L2, while in the bedrock it is greater than 2.00 km/s. (from Bertolini & Gorgoni, 2001).

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average, that accumulated in only 10 days. The 20 and 21 describe the one-year data output from the volume of the slope involved in the year 2000 event gauges. was about 2.5*106 m3. The average thickness of the The data shows that: block, as demonstrated by inclinometric gauges, is • the area affected by post-event movements is 35 m. The measured displacement during this event larger than the area affected by the 2000 event; was approximately 60-80 m in the lowest part of the • a limited amount of rainfall may cause a slope, and a few decimetres inside the village, which noticeable rise in the water table; is located on the crown of the actual slide. • snowmelt causes a very large increase in the The crown has moved uphill approximately 50 m in water table. the last 50 years. The region’s historical records show To conclude, it is important to stress the effi ciency of that the same slope was affected four times in the the monitoring system and, in particular ,the value of last century. An older village had been completely the motorised theodolite; it has not failed during two destroyed in an event in 1947, and then was relocated years of monitoring. to its present-day position, where it was damaged The major problem related to the reconstruction again in 1972. of “new Poviglio” is that the new location must In 2001, the regional government allocated funds not be too far from the original site, because the for the construction of a new village, and a special inhabitants want to stay as close as possible to their technical committee found a safe site. The building farms. Another problem will be a new Regional law of “New Poviglio” will take two to three years. In requiring the destruction of the old hamlet, even if the the meantime, 20 villagers will remain in the existing buildings are not damaged. Poviglio thanks to a sophisticated monitoring system composed of automatically driven gauges (a Itinerary F description - From Poviglio (Stop 2.2) motorised theodolite, a three-base extensimeter and to Canossa: one piezometer). All data are transmitted in real-time Large expanses of Epi-Ligurian clayey breccias (the by GSM. In addition, satellite-based InSAR surveys “Canossa olistostrome,” Late Oligocene-Burdigalian were made by Telespazio s.p.a. Figures 17, 18, 19, in age) are visible in outcrop within the large area of Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 16 - Lavina di Roncovetro: the graph shows the trend through time of groundwater level measured on L1 inside a 40-m-deep open-pipe piezometer with n automatic daily recording. It can be noticed that in concomitance with main reactivation (c and d), sudden uplifts of the water table occur (line-b), although they are disproportionate to the preceding rainfalls (histogram-a). This data, together with other factors discussed in the text, point to a groundwater feeding from deep subsoil sulphate waters (from Bertolini & Pellegrini, 2001).

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini The olistostromeisformedbysubmarinemudfl badlands, seenontheapproachtoCanossaCastle. (Eocene); 6. Arenarie diPonte Bratica(Oligocene);a.fi debris deposits;3.poorly-consolidatedclaybreccia;4.overconsolidated claybreccia;5. Argille eCalcaridiCanetolo Figure 17-Schematic cross-sectionofthePoviglio landslide.Legend:1.Continuous-coreborings; 2.superfi the few remainingruinsisquite disappointing. Unlike attracts many German tourists,althoughtheview of during thelastcenturies. The historyofthecastle castle was almostcompletelydestroyed several times and German(“nachKanossagehen”). The Canossa to Canossa”means“humblehimself”bothinItalian memory ofthoseevents, even todaythe saying“togo Dante asanextraordinary example ofanactive life.In in St.Peter’s cathedralinRome.Shewas glorifi the solewoman tohave theprivilege ofbeingburied defender ofthe Vatican’s power andthat’s whysheis excommunication. Matildealways was avaliant before andbegged PopeGregory VII torepealhis the GermanEmperorHenryIV, barefoot,kneeled Europe duringthe War ofInvestitures: here,in1077, of themostimportantcentrespower inmedieval of CountessMatildediCanossa(1046-1115)andone formed byMiocenesandstones.Itwas theproperty Canossa castle(Figure11)sitsuponasteepcliff it aresandstonesoftheBismantova Group. m thickandshows ablock-in-matrixstructure. Above satellite Miocenebasin. The olistostromeisabout150 the underlyingLiguriannappeanddepositedin and debrisfl ows, resultingfromthereworking of ed by ows ssured; 7.rupturesurface(fromBeretti,2003). We willpassthroughLigurianfl (Stop 3.1). Itinerary Gdescription Topic oftheday: produced), andfi in whichthecharacteristic“ marvellous castle ontheright),Langhirano(aregion Parma River, passingthrough Torrechiara (noticethe to Pannocchia, andthenheadupstreamalongthe From theCastleofRossena,wecrossPoplain Canossa-Corniglio-Florence Itinerary have dinnerandlodge. nappe duringitstranslationalmovement. Here we’ll off fromthe“Ligurian”oceanfl Ophiolite isamassofpillow lavas whichwas sheared from thecolourofrock, of theLigurianDomain. The name“Rossena”derives of redophiolitelyingwithintheChaoticComplexes of Matilde. They arelocateduponacliff composed tower arewellpreserved. They also weretheproperty Canossa, Rossenacastleandthenearby“rossanella” nally Corniglio. thelarge CorniglioLandslide. DAY 3 –fromCanossatoCorniglio Prosciutto diParma oor bytheLigurian rosso ysches (theMonte meaningred. cial] 25-05-2004, 13:25:08 ” is LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Figure 18 - Poviglio landslide: the dashed line delineates the year 2000 landslide event. The vectors indicate the direction and total displacement (in mm) measured over one year by the motorised theodolite. The area involved by these post-event displacements is greater than the actual area affected by the year 2000 event (from Beretti, 2003). Volume n° 3 - from DO1 to P13 n° 3 - from Volume

Figure 19 - Poviglio landslide: Inclinometric curve showing a double rupture surface at depths of 36 and 15 m (from Beretti, 2003).

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini (n.1) iscausedbytheinfi that 45-90mmrainfallsover two-three daysraisedthewater tableby2-3meters(n.3).The6-metrelong-lastingrise Figure 20-Poviglio landslide:comparisonbetween dailyrainfall(histogram)andwater tabledepth(line).Itisnotable ltration ofsnowmelt waters, followed byasuddendecrease(n.2)(fromBeretti,2003). September 2003. Photos byGiovanni Bertolini, village inasafer area. the constructionofnew to remainintheirhousesduring movements, enablingvillagers theodolite surveys thelandslide’s the automaticmotorised Figure 21-Poviglio landslide: 14-06-2004, 14:31:23 LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

Sporno and Monte Caio Formations) until Ghiare. We main landslide movement has also caused dragging then pass through the Sub-Ligurian Units (Canetolo effects, with deep-seated rotational failure surfaces Unit Auctt) of “Argille e calcari” (a clayey and and displacements of up to some decimetres recorded block-in-matrix structured unit, alias the “Mèlange simultaneously with each reactivation. Displacement di Lago”), the Arenarie di Ponte Bratica Formation vectors, variable both in space and in time, and (thinly-bedded, arenitic Eocene turbidites), until we sometimes even of opposite directions, have been reach Corniglio. recorded within the same inclinometer, according to the different tension states determined by the main Stop 3.1: landslide body. The large Corniglio Landslide The formations bounding the landslide body belong by Gianfranco Larini and Claudio Malaguti to the Ligurian and Sub-Ligurian sequences, and The Corniglio landslide is a large mass movement are made up of calcareous (Mt. Caio Formation) and (Figures 22 and 23) which has affected the old arenaceous (Arenarie di Ponte Bratica Formation) village of Corniglio (700 m a.s.l.), a medieval fl ysches, chaotically arranged clay shales (Argille hamlet, on several occasion during the past 400 e Calcari, Melange di Lago) and Quaternary slope years. Total reactivations of the landslide were deposits of various origins. All the rock types cropping recorded in the years 1612, 1740 and 1902, but the out in the area are highly tectonised, lithologically- evidence collected shows that other movements had and structurally-complex formations (“weak rocks”). occurred in previous times, as documented also in They are therefore subject to intense and rapid the land registry of 1559, in which the term “Lama” weathering, eventually turning into clay matrix debris is reported. Its present dimensions are considerable: covers. According to water content, their consistency over 3000 m long, 1000 m wide and up to 120 m deep, can reach the plastic or even liquid state, thus causing stretching from an altitude of 1150 m to 550 m a.s.l., large earth fl ows. The landslide causes are ascribable in correspondence with the torrent Parma riverbed, in to a decrease of geomechanical parameters, owing to an area characterised by an annual mean rainfall of weathering processes. 1500 mm. After a long period of dormancy lasting In the short term, the causes of instability result nearly a century, in mid-November 1994 this vast instead from an increase of porewater pressures, after landslide, classifi ed as a slow, intermittent complex periods of intense rainfall. The whole upper Parma and composite landslide, resumed its activity striking River valley is affected by several landslides which once more the village of Corniglio. The landslide, are also connected to the Late-Pleistocene morpho- which has developed within arenaceous and climatic processes, when two glaciations (Riss and calcareous fl ysches overlying chaotically arranged Wurm) deeply altered the outcropping rock types clay shales and limestones, consists of multiple by forming thick slope deposits. According to the rotational-translational slides in the upper part, evidence collected during the investigations carried associated with earth fl ows (up to 20 m in depth). The out in the fi ve past years, the landslide body does not total volume is about 0,2 km2. A new phase of urban seem to have ever reached truly stable conditions. In development started in the early 1970s and continued 1995, during a dormant phase, consolidation efforts until 1994, with the construction of some 70 new were made: thousands of trees displaced by the houses and 5 industrial buildings, mostly built on the landslide were cut down, new topographic mapping old landslide accumulation zone. The displacement of the landslide was performed, the runoff network measured during two recent reactivations, occurring was re-established, draining trenches were dug to a in the 1994-1996, period showed that the landslide’s depth of 12 m, and seismic investigations (refraction frontal part has undergone a displacement of about prospecting, down-hole and cross-hole tomography) 50 m, with consequent partial damming of the were carried out. DO1 to P13 n° 3 - from Volume Parma riverbed. Moreover, displacement of some Early in 1996, a large new detachment occurred centimetres has been recorded along the whole ridge along rotational slip surfaces. In February 1996 the made up of an arenaceous fl ysch (the Sub-ligurian formation of tension cracks in the ground and fi ssures Ponte Bratica Formation) delimiting the landslide’s in several buildings and streets of the village followed eastern fl ank, where the rest of the village lies, with mass re-mobilisation of the ancient landslide body. displacement vectors aiming both at the Torrente One inclinometer showed moderate deformations Bratica (eastward) and at the landslide’s body. Indeed, along the whole tube, up to its lowest extremity (80 on this highly fractured arenaceous formation the m in depth). Monitoring equipment has been further

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini 3) dormantlandslides;4)Colluvialdebris deposits;5)gelifl 2) active landslidesincluding“laLamadiLinari”landslide(a)andtheCorniglio-Coloniaridge landslide(b); Figure 22-GeologicalmapoftheCorniglio Landslide.Legend:1)present-dayandrecentalluvialdeposits; continuation; 11)faultburied byslopedeposits;12)overthrust (fromLarinietal.,2001). Ponte Braticatype(c);7) Arenarie diPonte Bratica;8)Mt.CaioFlysch; 9)layerattitude;10)thefaultanditspossible with calcareousfragments(a),arenaceousofthe Arenarie diPetrignacola type(b)and Arenarie di uction deposits(UpperPleistocene);6)MélangediLago, 14-06-2004, 14:31:52 LANDSLIDES OF THE EMILIA APENNINES (NORTHERN ITALY) P13

landslide body during the past 30 years. Conclusions During recent years the Italian territory has been hit by destructive landslides several times. Events including the Sarno, Valtellina, Soverato, Val di Stava and Corniglio landslides have caused the public to demand increased protection. People are now ready to accept new regulations and restrictions, but they want clarity from the geological community. This community has a responsibility: excessively prudent management could inhibit human activity in terms of growth, even when local conditions might permit such activity. On the other hand, the previous situation of deregulation led to extremely dangerous conditions. Figure 23 - Aerial view of the Corniglio Landslide (16 January 1996, courtesy of Recent progress Compagnia Generale Riprese Aeree). Italian Air Force authorization #.I-46 of 30/01/ 96. Legend: FC = Mt. Caio Flysch; AC= Mèlange di Lago; ABR= Arenarie di Ponte During the last decade great Bratica; 1c= crown zone; 1s= main scarp; 1= rotational slide (February-April 1996) progress has been made: along a failure surface deeper than 100 m; 4= portion of landslide not reactivated; • today we have clearly 22= Lumiera area, where NNW displacements occurred in February-April 1996, identifi ed the positions, afterwards partially annulled by displacement in opposite direction; 5= rotational shapes and dimensions slides within ABR, with formation of trenches and para-karst depressions; 21= Colonia of the region’s landslides area, showing displacements exceeding 80 m in depth; landslide sectors reactivated in bodies; 1902 (from Larini et al. 2001). • the large improved with the setting up of an Automatic landslides represent the Inclinometric System and electric piezometers with superimposition of several relatively more minor automatic data acquisition to safeguard the most mudslides, which occurred during previous periods of worsened climate. They are a result of multi- important built-up area. All the interventions carried phase events occurring over a period of several

out so far have been aimed at risk mitigation, including DO1 to P13 n° 3 - from Volume thousands of years; the Parma stream hydraulic risk resulting from the • we know that the present-day landslide activity is partial damming of its riverbeds. Consolidation directly related to the intrinsic instability of those measures, consisting of drainage systems, were ancient landslide bodies, and that their dormancy carried out near Corniglio, where slower and low- period may last months, years, or decades; intensity displacement occurred. Most of the costs • above all, we have learned that the geological and for these restorative measures (which roughly amount recent history of the large landslides is important in to 20.000.000 Euros) have gone for interventions on order to understand their present-day behaviour. the houses, storehouses and structures built on the

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Volume n° 3 - from DO1 to P13 P13 - P13 Leader: G.Bertolini Provincia diReggio -Emilia). di Roncovetro (Vedriano, ComunediCanossa, Bertolini G.andGorgoni C. (2001)-Lalavina Italy. della Regione Emilia-Romagna.SystemCart,Rome, (2002). CartadellaPericolositàRelativa daFrana Egidi D.,MainettiM.,PignoneR.andPizzioloM. Bertolini G.,CanutiP., CasagliN.,DeNardoM.T., Modena andReggio Emilia.Modena,Italy degree thesis.GeologicalDepartment,University of Ramiseto (AppenninoSettentrionale).Unpublished Beretti P. (2001).LafranadiPoviglio inComunedi Bibliography: techniques. utilizing long-termmonitoringandearthobservation , andmeasuringmotionataninstrumental-scaleby include thecontinuousupdatingofcartography failure, orhazard,inprobability. Otheressentialtasks very effective instrumentsindefi Historical researchandreal-timemonitoringare Future goals but itcannotforecastlarge-scale landslides. in ordertoassessthetriggeringmechanisms(causes), stability analysesandnumericalmodellingisuseful landslides. A deterministicapproachincluding (not dangerous)from“dormant”(still landslides, but wecannotyet distinguish“relict” we candistinguishbetween“active,” and“inactive” for yearsordecades,ismorediffi related tomoreinactive landslides,thosenotmoving them. Instead,defi understands thelandslide-relatedhazardandavoid in regards totheirrisk-management:thepopulation Active mudfl Problems interventions. 1994-1999 periodandrequiredCivil Protection reference tothosewhichresumedactivity inthe of theEmilia Apennines (northernItaly)with Bertolini G.andPellegrini M.(2001). The landslides Pitagora Editrice,Bologna,Italy. of theEmilia-Romagna Apennines. In Bertolini G.andPellegrini M.(2003). The landslides Bologna, Italy. Geotermia Poszukiwan Geologicznych Geosynoptyka i C. (2003).RadiocarbondataonLateglacial and Bertolini G.,CasagliN.,ErminiL.andMalaguti Krakow, Poland. Research InstituteofthePolish Academy ofSciences, , 3 ows andmudslidesarenotproblematic , 19-27,MineralandEnergy Economic Quad. Geol. Appl ning andexplaining thehazard Quad. Geol. Appl. . 8,PitagoraEditrice, cult. Inmostcases ning the rateof Technika

8 , (Italy). Holocene LandslidesintheNorthern Apennines Geol. Appl Parmense), riattivata negli anni1994-1999. C. (2001).“LaLama”diCorniglio(Appennino Larini G.,MalagutiC.,Pellegrini M.and Tellini Geol. D’It., in Italiadaldopoguerraal1990. Catenacci V. (1992).Ildissestogeologicoeambientale Japan. Heritage Mitigation andProtection ofCultural andNatural slope movements. ground-based radarinterferometrytomonitor A.J. and Tarchi, D. (2002) Someapplicationsof Canuti, P., Casagli,N.,Leva, D.,Moretti,S.,Sieber, 523-528. Balkema ed.Prague,Czech,,. Proceedings 1stEuropean Conference onLandslides Rybar, J.StemberkandP. Wagner (eds.), by usingground-basedradarinterferometry. In:J. A.J. and Tarchi, D. (2002) Landslidemonitoring Canuti, P., Casagli,N.,Leva, D.,Moretti,S.,Sieber, 243-250. Rome,Italy delle frane. Canuti P. andEsuF. (1995):Glossariointernazionale Appl reactivated inthe1994-1999peroiod. to therockunitscroppingoutinareasoflandslides Outlines ofEmilia Apennines (Italy)andintroduction Bettelli G.andDeNardoM.T. (2001).Geological Publishers, Netherland. Richmond, B.C. -Multilingual LandslideGlossary. BiTech Publishers, Inventory andCanadianGeotechnicalSociety(1993) WL/WLI Working Party onthe World Landslide Regione Emilia-Romagna, Bologna,Italy Pizziolo M.(1996).CartaInventario delDissesto. Soc. Geol.It. (Appennino settentrionale,Provincia diParma). morfologiche dellaGrandeFranadiCorniglio Marchi G.(1998).Caratteristichegeologichee Pellegrini M., Tellini C., Vernia L.,LariniG.& Quaternario ad EarlyHolocenechronologyandpaleoclimate. Orombelli G.andRavazzi C.(1996). The LateGlacial Geol di Maltalandslide(northern Apennines, Italy. monitoring ofmassmovements: application toCà Systems anddigitalphotogrammetryforthe Mazzini E.andPesci A. (2003).GlobalPositioning Mora P., BaldiP., CasulaG.,Fabris M.,Ghirotti M., Italy. ., ., 8 68 Natural Hazards , 1-26,PitagoraEditrice,Bologna,Italy. , 1-2,103-121,Rome,Italy. 357-374. UNESCOandKyoto University, ., 47 ,

Rivista ItalianadiGeotecnica 8 53 9 , Rome,Italy. , 59-114,PitagoraEditrice,Bologna, (2),439-444, Rome,Italy. , 543-561,Rome,Italy Proc. Int.Symp.LandslideRisk

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