Geomorphological Hazard and Tourist Vulnerability Along Portofino Park Trails (Italy) P

Geomorphological hazard and tourist vulnerability along Portofino Park trails (Italy) P. Brandolini, F. Faccini, M. Piccazzo

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P. Brandolini, F. Faccini, M. Piccazzo. Geomorphological hazard and tourist vulnerability along Portofino Park trails (Italy). Natural Hazards and Earth System Sciences, Copernicus Publ. /Euro- pean Geosciences Union, 2006, 6 (4), pp.563-571. hal-00299331

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HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 www.nat-hazards-earth-syst-sci.net/6/563/2006/ Natural Hazards © Author(s) 2006. This work is licensed and Earth under a Creative Commons License. System Sciences

Geomorphological hazard and tourist vulnerability along Portoﬁno Park trails (Italy)

P. Brandolini1, F. Faccini1, and M. Piccazzo2 1DISAM Department, University of Genoa, Italy 2DIPTERIS Department, University of Genoa, Italy Received: 26 July 2005 – Revised: 7 April 2006 – Accepted: 7 April 2006 – Published: 27 June 2006

Abstract. The many trails existing in the coastal area of Swarbrooke et al., 2003). This phenomenon has led to in- Portofino Promontory are used by tourists for trekking or as creased risk and environmental impact, as in the case of pathways to small villages and beaches. The aim of this pa- Portofino Natural Park in the northwestern coastal sector of per is to define geomorphological hazard and tourist vulner- Italy; Portofino is an Italian seaside tourist resort of interna- ability in this area, within the framework of the management tional renown. and planning of hiking activities in Portofino Natural Park. The boom in hiking and related tourist activities along the In particular, processes triggered by gravity, running wa- steep slopes of the promontory, which are frequently affected ters and wave motion, affecting the slopes and the cliff, are by instability phenomena, has brought about an increase in considered. The typology of the trails and trail maintenance accidents involving visitors to the area. Data collected by are also taken into account in relation to weather conditions the C.N.S.A.S. (National Alpine and Speleological Rescue that can make the excursion routes dangerous for tourists. Corps) on rescue operations performed in a recent five-year In conclusion, an operative model is applied for the defi- period (1999–2004) on the park trails, show an average of nition of possible risk scenarios. This model is founded on 5–6 major rescue efforts per year, involving a total of 28 per- an inventory and the quantification of geomorphological haz- sons. ards and tourist vulnerability, in comparison with trail rescue data. The model can be applied to other environments and Taking the concept of risk (Varnes, 1984; Panizza, 1987; tourist areas. Bell, 1999; Grecu et al., 2003; Glade et al., 2005) as the starting point and defining it as a product of hazard and vulnerability, an operative model has been applied for the assessment of possible risk scenarios, and tested in several morpho- 1 Introduction climatic environments within the framework of the Ministry of Education, University and Research project “Geomorpho- Research focused on geomorphological hazard associated logical heritage as a resource for sustainable tourism” (Bran- with tourist activities and facilities is currently taking on dolini et al., 2004a, b). This model analyzes geomorpholog- great importance because of hazard-related environmental ical instability phenomena, together with the structural fea- and socioeconomic ramifications. This trend is particularly tures characterizing the trails. In the case of particular mete- pertinent in the case of vast areas of the Alpine and Mediter- orological conditions (e.g. heavy rainfall, high temperatures, ranean regions. winds), the latter can contribute to increasing the risk of ac- Tourism has led to the occupation and utilisation of ar- cidents, as can the level of physical fitness and the technical eas marked by ever-increasing geomorphological fragility. skills of visitors. There has been an enormous increase in the number of visitors – visitors who are often inadequately prepared (in terms The aim of this study is to improve the above-mentioned of skills, experience and equipment) – to areas considered model, in order to make it applicable to a larger number virtually inaccessible just a few decades ago, in both high of morphodynamic environments and tourist areas. Greater mountain and coastal sectors (Dowling and Newsome, 2005; knowledge about the geomorphological hazards associated with hiking and trekking activities can contribute to making Correspondence to: P. Brandolini tourists more aware of natural phenomena and risky situa- ([email protected]) tions (Solana and Kilburn, 2003).

Published by Copernicus GmbH on behalf of the European Geosciences Union. 564 P. Brandolini et al.: Geomorphological risk in Portoﬁno Park (Italy)

300

S.Rocco Camogli 250 Semaforo Nuovo S.Margherita Nozarego

200 summers and mild winters; b) a mid-hill zone on the northern slope, with lower mean winter 150

temperatures and higher ramm (rainfall) 100infall, especially in the sectors exposed to the N.

In general, maximum rainfa50ll occurs in the autumn months, whereas the minimum takes place in the summer months (Fig.0 2). Annual mean rainfall varies between 1000 and 1400 mm (Fig. april may june july march august january february october 3) and the annual mean temperature ranges between 12september and 13°november decemberC, reaching a 23-24° C peak in the summer and a lowFig. of 2.7-Distribution8°C in the of annualwint meaner. rainfall.

Fig. 1. Location of the study area. High-altitude (12 500 m) aerial photograph of the Promontory of Portoﬁno (Flight Italia 94 – Con- sorzio Compagnie Aeronautiche, Parma).

2 General framework

Situated about 25 km E of Genoa, the Portofino Promontory abruptly breaks up the continuity of the coastline between Genoa and Sestri Levante and covers a surface area of about 18 km2. It was declared a protected area in 1935. The promontory is a massive and prominent SSW pro- jection clearly differentiating the virtually rectilinear pattern of the surrounding coastline (Fig. 1). Considerable vari- ability of the morphology can be observed on the western Fig. 3. Isohyet map with meteorological stations. side, where the promontory extendsFigur ine a 3. N-S Isohye directiont map and with meteorological stations. is almost rectilinear between Camogli and Punta Chiappa for about 3 km. The eastern side is virtually parallel to the In general, maximum rainfall occurs in the autumn western side, with a heightened complexityWinds from and acoastal the S ex- are wmonths,arm and whereas satura theted minimum with w takesater placevapour in theaft summerer crossing wide expanses of tension of about 8 km. The inlets of Cala dell’Oro and San months (Fig. 2). Annual mean rainfall varies between 1000 Fruttuoso are located on the southernsea. side,As whichthey presentsencounter andand 1400 cli mmmb (Fig.the 3)nat andura thel ba annualrrier meanof th temperaturee Promontory, the temperature a general E-W orientation and extends for a length of about ranges between 12 and 13◦C, reaching a 23–24◦C peak in 6.5 km. decreases, causing condethens summeration of and la arg lowe a ofm 7–8ount◦Cs in of the w winter.ater, especially in the summer. This is Mt. Portofino (610 m a.s.l.) is the highest orographic largely due to the temperaWindsture fromgrad theient S be aretw warmeen andthe saturatedair and with the waterrock discontinuities. This elevation on the promontory. It stands on the divide vapour after crossing wide expanses of sea. As they en- that is subparallel to the southernproc shoreline,ess suppl whereies sev-the numcountererous andpere climbnnia thel spri naturalngs, barrierwhich of a there a Promontory,lso found at high altitudes (Fig. eral smaller peaks are observable, among which Mt. Tocco the temperature decreases, causing condensation of large (543 m a.s.l.), Mt. delle Bocche (5064). mT a.s.l.)hese andspri Mt.ngs Pol- have amountsbeen us ofed water, sinc especiallye histori inca thel ti summer.mes and This ar ise largelystill used today by trekkers lone (465 m a.s.l.). due to the temperature gradient between the air and the rock The climate of the promontory isan conditionedd visitors by (F theac mor-cini et aldiscontinuities.., 2005). This process supplies the numerous peren- phology, so that it can be subdivided into two zones: a) a nial springs, which are also found at high altitudes (Fig. 4). typically Mediterranean one on the southern slope, with dry, These springs have been used since historical times and are warm summers and mild winters; b) a mid-hill zone on the still used today by trekkers and visitors (Faccini et al., 2005). northern slope, with lower mean winter temperatures and The geological profile of the Promontory can be schemat- higher rainfall, especially in the sectors exposed to the N. ically indicated as Conglomerate overlying Flysch, along a

Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 www.nat-hazards-earth-syst-sci.net/6/563/2006/

Figure 4. Geological sketch map: 1. Flysch; 2. Conglomerate; 3. Fault or fracture; 4. Attitude; 5. Water spring.

4 P. Brandolini et al.: Geomorphological risk in Portofino Park (Italy) 565 contact with a SSW dip direction (Fig. 4). The Flysch, dat- ing from the Upper Cretaceous – Paleocene (Corsi et al., 2001), is made up of marly limestone with thin interlay- ers of clayey shales, sandstones and calcarenites. The Con- glomerate (Oligocene) consists of marly limestone pebbles ranging in diameter from centimetres to meters. Arena- ceous elements are present to a minor extent, and other rock types, among which ophiolites and cherts, are even less frequent. The pebbles are embedded in a matrix that is generally calcareous-arenaceous, and sometimes quartzose or clayey. The Conglomerate presents an average overall SSE dip direction in the western sector and SSW in the eastern sector, with a dip of 10◦–20◦. Interrelations between the geomorphological elements and Fig. 4. Geological sketch map: 1. Flysch; 2. Conglomerate; 3. Fault tectonic lineations are observable, as follows. In addition or fracture; 4. Attitude; 5. Water spring. to the faults delimiting the Promontory of Portofino, the drainage pattern and the watershed ridges, including both major and minor ones, all appear to be arranged on fracturing 3.1 Geomorphological hazard and fault lines, with the systems being oriented WNW–ESE, NNE–SSW, N–S and E–W. Geomorphological dynamics on the promontory are characterized by landforms and processes triggered by gravity, running waters and by the action of the sea (Fig. 5). 3 Methods Active landslides are prevalently concentrated on the western slope, between Camogli and San Rocco, where rockslide The research was based on the following survey and data- and rockfall phenomena are observable and affect residen- processing phases: a) definition of general background in- tial areas, paths and other infrastructures (De Stefanis et al., formation concerning the area or the tourist route, b) survey 1984; Terranova, 1999; Brandolini et al., 2005). Additional of the geomorphological hazard, c) survey of the structural mass movements are observable along the main watershed morphological elements and the geoenvironmental elements ridge zone, where they are aligned along the contact be- that may affect trail vulnerability, d) definition of tourist vul- tween the Conglomerate and the underlying Flysch. In this nerability, and e) definition of possible risk scenarios. case, the landslides, which are essentially dormant, are de- Risk assessment takes into account factors relating to ge- termined by the geomechanical contrast between the forma- omorphological hazard and factors relating to tourist vulner- tions described above. This leads to slowly developing lateral ability (Brandolini et al., 2004a). Three simplified classes of spread types of movement (Pietre Strette) or complex types risk (i.e., Low, Medium, and High) are defined using a Geo- of movement, a sort of combined rockfall and debris flow graphic Information System (GIS). (Gave). Lastly, phenomena such as rockfalls and topples are The geomorphological hazard factors include all the natu- frequent along the active cliff bordering the entire promon- ral processes that may affect hikers in any way along a trail tory. Near Santa Margherita Ligure, in particular, talus cones (e.g. types of processes, states of activity, morphometric fea- and scree slopes are created at the base, especially in the tures, frequency, conditions of the bedrock). Besides the marly limestone, and they supply material to the gravelly- components regarding the trail considered as an infrastruc- pebbly pocket beaches, often through steep ravines. ture (e.g., characteristics and structure, state of preservation, Landforms and processes due to running waters can be ob- steepness, exposure, and presence of protective devices such served throughout the promontory. The debris flows in the as barriers or railings), tourist vulnerability includes aspects western sector of the promontory are particularly important relating to the vulnerability of hikers. These latter aspects in terms of geomorphological dynamics (Schumm, 1994; De may be subdivided according to the elements characterising Chano and Butler, 2001). Moreover, colluvial deposits cov- the tourist influx (e.g. type and magnitude of the tourist in- ering the contact between the Flysch and the Conglomerate flux, presence of infrastructures) and on the basis of the ty- are found in the upper portions of this slope. The deposits pology of visitors (e.g. sex, level of knowledge and aware- present thicknesses in the range of several meters in some ness, physical and psychological preparation, equipment). cases and they have often been reworked into terraces for Although this latter variable is very important for the identifi- agricultural use. The drainage pattern on the southern slope cation of possible situations characterised by the interaction is steep, very brief and with heavy rainfall, it causes marked between natural hazards and visitors to the area, it was not transport of solids, resulting in serious geomorphological in- taken into account in this specific case, owing to difficulty stability phenomena along the longitudinal profile. The flood with insertion in the matrices used to define risk levels. of 1915 is one example of such an event, an event that led to www.nat-hazards-earth-syst-sci.net/6/563/2006/ Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 566 P. Brandolini et al.: Geomorphological risk in Portofino Park (Italy)

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Fig. 5. Geomorphological map: 1. Colluvial deposit; 2. Landslide and debris cover; 3. Conglomerate; 4. Flysch; 5. Edge of degradational or landslide scarp; 6. Direction of movement; 7. Edge of scarp due to wave erosion; 8. Rock fall direction; 9. Planation surface; 10. Pocket beach; 11. Trail; 12. Build up area.

Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 www.nat-hazards-earth-syst-sci.net/6/563/2006/ P. Brandolini et al.: Geomorphological risk in Portoﬁno Park (Italy) 567

rescue 1999-2004 (from CNSAS) rescue days

10 10 9 9 8 8 7 7 6 6 5 5 4 n° rescue 4 n° rescue 3 3 2 2 1 1 0 0 1999 2000 2001 2002 2003 2004 friday sunday tuesday monday thursday saturday

total rescue man woman wednesday

rescue months rescue tracks

10 16 9 14 8 12 7 10 6 5 8 6 4 n° rescue n° rescue 3 4 2 2 1 0 0 july nuovo may april june Base 0 chiappa Batterie- march Gaixella- august january october february M.Portofino S.Fruttuoso november december S.Fruttuoso- S.Fruttuoso- pietre strette september oca-semaforo S.Rocco-punta T Olmi-Nozarego Portofino-vitrale

range of ages meteorologichal conditions

12 10 10 9 8 8 7 6 6 5 4 n° rescue n° rescue 4 3 2 2 1 0 0

under 10 10-18 19-30 31-40 41-50 51-65 over 65 sunny cloudy light rain heavy rain

total rescue man woman partly cloudy

Fig. 6. Rescue data in the 1999–2004 period (source: Corpo Nazionale di Soccorso Alpino e Speleologico – C.N.S.A.S.). the formation of San Fruttuoso beach, which had disappeared line with respect to dominant currents and in relation to the previously owing to marine erosion. existing rock types and their geomechanical characteristics. Along the coastal strip of the park, wave action takes on As mentioned previously, erosion by wave motion has pro- an important role as regards both the orientation of the coast- duced a cliff that reaches a height of over 25 m. It is a very www.nat-hazards-earth-syst-sci.net/6/563/2006/ Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 568 P. Brandolini et al.: Geomorphological risk in Portoﬁno Park (Italy)

forts per year (Fig. 6). In a total of 28 operations, 9 men and 19 women were assisted; the age range was between 30 and 60 years. As expected, the data revealed a concentration of rescue operations between May and September, that is, the summer months when there is a major influx of tourists. The distribution of the rescue efforts, however, proved to be scat- tered throughout the days of the week. The trails showing the largest number of incidents are those leading to the hamlet of San Fruttuoso (Fig. 7), that is, one trail in the western sector starting from Batterie, one in the northern sector starting from Pietre Strette, and another in the eastern sector starting from Base 0, amounting to 13, 7 and 5 rescue efforts respectively, or about 75% of the total. A comparison between the weather conditions and the number of rescue operations revealed a multimodal distribu- Fig. 7. Detail of San Fruttuoso bay, one of principal hiking/tourist tion, although a substantial number of rescue operations took destinations, with its two very popular small beaches. place when weather conditions were prevalently characterized by sunny weather or drizzle. characteristic feature of the southern slope with its typical series of promontories and inlets, among which we note the 4 Results inlets of San Fruttuoso and Cala dell’Oro. As concerns geomorphological hazard, the Portofino Natural With its characteristic conglomeratic block, which Park trails can be subdivided into 4 sectors according to their projects further out than the surrounding coast, the promon- particular characteristics: tory’s particular coastal morphology is thought to be linked more to recent tectonic events than to other exogenetic – the western sector, between Punta Chiappa and agents. If the conglomeratic rock mass were not endowed Camogli. The sector presents a continuous cliff that ex- with good intrinsic stability, marine erosion would surely ceeds 25 m in height. Due to fracturing of the rock mass, have carved it out to a more pronounced degree. In fact, the the cliff is the source of rock falls and rock slides. The slopes facing SSW are particularly exposed to wave cutting portions above the Poggio, Galletti and Mortola ham- by rough seas with southwesterly currents, which carve them lets are characterized by significant active and inactive out frontally, and by those with southeasterly currents, which landslide scarps (De Stefanis et al., 1984; Brandolini et scour them. al., 2005);

3.2 Trail and tourist vulnerability – the eastern sector, between Punta Portofino and Santa Margherita Ligure. The sector presents a modelled cliff The promontory features a dense network of trails, with the only in the Conglomerate, mainly between Punta del routes covering more than 70 km on steep slopes, unwinding Coppo and Punta Portofino, and between Punta della through a surface area slightly exceeding 1000 ha, and rang- Cervara and the Paraggi castle. Rock topple and rock- ing in elevation from sea level up to more than 600 m. fall phenomena may occur along the rock wall owing to With departure points from San Rocco, Portofino Vetta, localized alteration of the Conglomerate; Nozarego and Portofino, which are the main park access lo- cations, the park paths vary in length and levels of difficulty. – the northern sector, situated along the Mortola, These are mainly old flagstone or unpaved dirt mule tracks Mt. Portofino, Mt. delle Rocche, Mt. delle Croci di leading to the principal arrival points, Punta Chiappa, San Nozarego and Mt. Brano alignment. The sector is char- Fruttuoso and Portofino, travelling through different mor- acterized by the primary superposition of the Conglom- phoclimatic environments. The trails are conditioned by the erate on the Flysch. As mentioned previously, owing to morphology of the area. In particular, the trails on the south- the marked geomechanical contrast between the Forma- ern slope leading to San Fruttuoso are steep, often with steps tions, vast mass movements are observable. Some are in the rock and narrow winding turns. There are sometimes active, among which the most well known are in the lo- difficult parts in ascent or descent, which make for a rather calities of Gave and Pietre Strette, in the upper part of taxing hike. the Fosso Magistrato and Santa Barbara basins. Along As mentioned in the introduction, the data collected by the the contact, which is very evident owing to differences C.N.S.A.S. on rescue operations performed on the trails in in steepness, there are continuous rockfalls and topples the 1999–2004 period, show an average of 5–6 rescue ef- along the discontinuities with northward orientations;

Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 www.nat-hazards-earth-syst-sci.net/6/563/2006/ P. Brandolini et al.: Geomorphological risk in Portoﬁno Park (Italy) 569

Fig. 8. Map of geomorphological risk along the trails in Portoﬁno Park: 1. Low; 2. Medium; 3. High.

– the southern sector, between Punta Chiappa and Punta tourists. However, these trails are also characterized by un- Portofino. The sector is characterized by a high cliff favourable infrastructural features. Generally speaking, they (over 100 m in height) modelled in the Conglomerate are very narrow trails, often without any form of protection, and broken up only by the Cala dell’Oro and San Fruttu- and they are poorly maintained. These hiking trails often lack oso inlets; the cliff represents a high-level geomorpho- any form of markings or signs providing information. Safety logical hazard. Potential kinematic mechanisms may equipment is also lacking. occur in the rock mass owing to the discontinuities. The crosscheck between geomorphological hazard and They consist of planar sliding with wedge and toppling tourist vulnerability thus led to the definition of a risk sce- failure modes, constituting an evident hazard for hikers nario concerning critical situations in vast sectors of the on the nature trail (Cevasco et al., 2004). trail network, but particularly on the southern slope of the promontory (Fig. 8). The risk was found to be high along In terms of tourist vulnerability, the trails on the southern all trails leading to San Fruttuoso, whereas it proved to be a slope of the promontory, between Punta Chiappa to the W medium-level risk along the trails leading to Portofino and al- and Punta di Portofino to the E, witness the highest flow of ways on the southern slope, which is steep and more exposed www.nat-hazards-earth-syst-sci.net/6/563/2006/ Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 570 P. Brandolini et al.: Geomorphological risk in Portofino Park (Italy)

ing levels of geomorphological risk affecting the excursion routes in this park. If adequately integrated with additional parameters, the proposed investigative model could be applied to other areas visited by tourists. The model could be adopted as an essen- tial tool serving to mitigate the risk connected with physical and anthropic components. Such efforts could be aimed at creating a heightened awareness of the interaction between trekking/hiking activities and natural phenomena, and thus also of hazardous situations. In conclusion, the data collected on this geomorphological environment could be made available to a wider public, ranging from the individual visitor, to Park Agency departments and staff, in the form of thematic geotourist or geoexcursion maps that are suitably condensed and simpliﬁed, and then generated and updated in the GIS (Geographical Information System) format. In turn, Park Agencies could utilize these maps as support for park area planning and management with the aim of safeguarding both the park and the park visitors, while also valorising the environment.

Acknowledgements. This work was carried out within the framework of the Ministry of Education, University and Research project “Geomorphological heritage as a resource for sustainable tourism” (COFIN 2004), National Coordinator: M. Panizza, and the local project of the Genoa University Research Unit on “Liguria’s geomorphological heritage as a resource for sustainable tourism”, Coordinator: M. X. Piccazzo. The authors wish to thank L. Sivori (C.N.S.A.S. – Tigullio Delegation) for the information supplied regarding rescue operations in the Park.

Edited by: T. Glade Reviewed by: V. Agnesi and another referee Fig. 9. The Caselle aqueduct trail (also known as “via dei Tubi”) is one of the most hazardous trails in the western sector of Portofino Park. References to weather and sea conditions. The risk levels determined Bell, F. G.: Geological hazards: their assessment, avoidance and for the trails using this approach appear to be consistent with mitigation, London, New York, E & FN Spon, 1999. the objective findings obtained from statistical analysis of the Brandolini, P., Farabollini, P., Motta, L., Motta, M., Pambianchi, G., Pelfini, M., and Piccazzo, M.: Geomorphologic hazards along rescue operations carried out in the park area. tourist itineraries: some examples from Italy’s territory, 32nd In- The Caselle aqueduct trail, which is undoubtedly the most ternational Geological Congress, Florence, 20–28 August 2004a. hazardous in terms of the geomorphological features in the Brandolini, P., Motta, M., Pambianchi, G., Pelfini, M., and Pic- study area, shows no recorded rescue operations in the pe- cazzo, M.: How to assess geomorphological risk in tourist areas. riod considered, as transit had long been banned due to nu- 32◦ International Geological Congress, Florence 20–28 August merous incidents in the past (Faccini et al., 2004). Today 2004b. the trail is used only by trekkers who are physically fit, Brandolini, P., Faccini, F., Robbiano, A., and Terranova, R.: Geo- adequately equipped and accompanied by authorized Park morphological hazard and monitoring activities in the western Guides (Fig. 9). area of Portofino Promontory (Italy), 14th Meeting of the Asso- ciation of European Geological Society, Turin, 19–23 September 2005. Cevasco, A., Faccini, F., Nosengo, S., Olivari, F., and Rob- 5 Conclusions biano, A.: Valutazioni sull’uso delle classificazioni geomecca- niche nell’analisi della stabilita` dei versanti rocciosi: il caso del The comparison and correlation of the geoenvironmental and Promontorio di Portofino (Provincia di Genova), GEAM, 111, tourist-related aspects described above clearly revealed vary- 31–38, 2004.

Nat. Hazards Earth Syst. Sci., 6, 563–571, 2006 www.nat-hazards-earth-syst-sci.net/6/563/2006/ P. Brandolini et al.: Geomorphological risk in Portoﬁno Park (Italy) 571

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