Lessons Learnt from the Snow Emergency Management of Winter Season 2008–2009 in Piemonte

Adv. Geosci., 26, 149–153, 2011 www.adv-geosci.net/26/149/2011/ Advances in doi:10.5194/adgeo-26-149-2011 Geosciences © Author(s) 2011. CC Attribution 3.0 License.

Lessons learnt from the snow emergency management of winter season 2008–2009 in Piemonte

R. Pelosini, S. Bovo, and M. Cordola Arpa Piemonte, Via Pio VII 9, 10135 Torino, Italy Received: 8 March 2010 – Revised: 7 May 2010 – Accepted: 28 June 2010 – Published: 16 February 2011

Abstract. The winter season 2008–2009 has been character- As shown in the Fig. 2, the gap of the mean daily new ized by heavy snowfalls over the western Alps. The snow- snow accumulation with respect to the climatology started falls have been exceptional because of their earliness, per- from November, increased in December significatively and sistence, intensity and territorial spread. The impact on the persisted throughout the spring season. regional environment and territory has been relevant, also As the snow in the mountain is concerned, see Fig. 3, the from the economical point of view, as well as the effort of 2008–2009 winter has been characterized by a large amount the people involved in the forecasting, prevention and fight- of new snow with respect to the climate, with snow amount ing actions. The environmental induced effects have been up to the 99% above the average. In three alpine sectors it shown until late spring. Several snowfall events affected also has been the snowiest season since 1966. the plains and the main towns, causing social impacts. The Several snowfall events affected also the plains and main purpose of this work is to describe the overall effects of the towns. 14 significant snow events have been recorded in Cu- anomalous snowfalls and the emergency response by the lo- neo and 9 in Torino from December 2008 to March 2009. cal government and institutions to face the hazard scenario The main one was in January 2009: 35 cm of new snow in and mitigate the risk for people, properties and environment. 36 h, with an intensity of 25 cm/24 h, the maximum intensity Arpa Piemonte (Regional Agency for Environmental Protec- recorded in the last 20 yr (the previous one was 17 cm/24 h in tion) gave the technical support to the snow emergency man- 1997). The intensity value is above the 90th percentile of the agement borrowing the expertise acquired during the heavy new snow measured in 24 h distribution considering only the hydrological events occurred in the Piemonte region and con- snowy days. These results agree with the 2008–2009 winter tributing to minimize losses. A short list of recommendations season snow anomaly studies on the southern alpine range came out from the experience, as well as the technical tools (e.g., Valt and Cianfarra, 2009). and products, all highlighting the emergency preparedness relevance. 2 Societal impacts of the snowfalls

1 The winter 2008–2009 heavy snowfalls The impact scenarios related to the snow emergency are different according to the geographical and anthropic territory The main critical situations have been arisen from the snow- features. During the winter 2008–2009 in the mountains, falls earliness in season, the several snow precipitation events several natural avalanche releases, characterized frequently over the plains, the big amount of snow accumulation on the by large size and heavy destroying power, affected villages ground, as well as the anomaly with respect to the last 30 yr and caused interruptions of the main and secondary road sys- climatic trend of snow conditions in the western Alps. The tems both down in the valleys and in small villages road ac- high-density snow depth manual station network (see Fig. 1) cess, requiring a long time for the complete and safe snow allows performing a reliable climatological analysis. removal and road re-opening. The avalanches often caused the service breakdowns and damages to the infrastructures in the built-up areas and to the forest heritage. The destruc- Correspondence to: R. Pelosini tive power of the avalanches was due to their characteristics: ([email protected]) the large amount of new snow triggered powder avalanches,

Published by Copernicus Publications on behalf of the European Geosciences Union. 150 R. Pelosini et al.: Lessons learnt from the snow emergency management

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1 Figure 2. TheFig. daily 2. amountThe daily of new amount accumulated of new snow accumulated measured by snow mountain measured weather by stations in mountain weather stations in winter 2008–2009 (pink line) and the 2 winter 2008-200930 yr climatology(pink line) and averaged the 30 years over clim theatology western averaged Alps (blue over line).the western Alps (blue 3 line).

4 As the snow in the mountain is concerned, see Fig. 3, the 2008-2009 winter has been characterized 5 by a large amount of new snow with respect to the climate, with snow amount up to the 99% above 6 the average. In three alpine sectors it has been the snowiest season since 1966.

1 Figure 1. The snow depthFig. 1.manualThe snow stations depth (blue manual dots) stations cons (blueidered dots) in considered this study. in In colours the Alpine this study. In colours the Alpine sectors (grey: Northern sector, light 2 sectors (grey: Northernblue: sector, North-western light blue: sector, North-western green: Western sector, sector, green: pink: Western South- sector, pink: South- western sector). 3 western sector)

4 As shown in the Fig.2, the gap of the mean daily new snow− accumulation withFig. respect 3. The to total the amount of new accumulated snow in the period characterized by high speeds (up to 350 km h 1) and strong 1 Figure 3. The total amount of new accumulated snow in the period November 2008 - May 2009 November 2008–May 2009 (blue) and in the 1996–2009 climatol- 5 climatology started frompressure November, over chalets, increased houses, in December mountain huts, significatively rural and graz- and persisted2 (blue) and throughoutin the 1996-2009 clim atology (red) for four alpine sectors (N, NW, W, SW) 3 ogySeveral (red) snowfall for events four affected alpine also sectors the plains (N,and main NW, towns. W, 14 SW). significant snow events have 6 the spring season. ing huts. For example, in the area around Ceresole Reale, a small village at 1570 m a.s.l. in the upper Orco Valley, in 4 been recorded in Cuneo and 9 in Torino from December 2008 to March 2009. The main one was in 5 January 2009: 35 cm of new snow in 36 h, with an intensity of 25cm/24h, the maximum intensity the period between the 15 and the 16 December 2008 many 6 telephone),recorded in the last determining20 years (the previous a one widespread was 17cm/24h in critical1997). The in situation.tensity value is above The avalanches occurred. Some of them have been classified as 7 urbanthe 90th percentile and commuting of the new snow measured traffic in during 24h distribution the considering snow emergency only the snowy days. en- extreme avalanches and flowed in areas where no avalanches 8 hancesThese results the agree difficultieswith the 2008-2009 related winter season to snow the anomaly road studies management on the southern alpine and 9 range (e.g., Valt M. and P. Cianfarra, 2009). were reported in the past, over crossing the limits of the offi- traffic control over the whole road system in the plains, even cial avalanche map. In particular, 4 simultaneous avalanches 10 with2 Societal little impacts snow of accumulationthe snowfalls on the ground. In the towns 3 11 The impact scenarios related to the snow emergency are different according to the geographical and occurred just above the village and destroyed 6 houses and the snowfalls determined several impacts: the urban traffic 12 ha of forest (Maggioni et al., 2009). 12 anthropic territory features. During the winter 2008-2009 in the mountains, several natural 13 slowedavalanche releases, up until characterized the completefrequently by large blockage, size and heavy the dest snowroying power, accumu- affected Moreover, the hydrogeological risk increased: the rocks 14 latedvillages and on caused the interruptions sidewalks of the andmain an parkingd secondary road areas systems for both several down in the days,valleys and wood transportation by canalized avalanches caused con- 15 theand in sidewalk small villages road iced, access, the requiring snow a long fell time from for the complete the roof, and safe tree snow branches removal and ditions prone to debris flows triggering (Tiranti, 2008) in the 16 crashedroad re-opening. along The avalanches the roads often andcaused temporarythe service breakdowns infrastructures, and damages to in-the 17 infrastructures in the built-up areas and to the forest heritage. The destructive power of the late spring and compacted snow accumulations caused the volving a large amount of people directly (discomforts, side- 18 avalanches was due to their characteristics: the large amount of new snow triggered powder water bags formation inside the snowpack, very dangerous walks snow removal, habit changes, difficulties in getting in case of sudden release (Bosco et al., 2007). Strong im- workplace, school closing. . . ) and asking for unexpected salt4 pacts have been recorded on the mountain wildlife also. supply. Critical situations due to the snow loading and the snow Negative indirect effects also arose from the road frost removal involved all the mountain people directly. Over the and intense freezing spells on the plains due to the snow plain and the hill country, where the new snow density was cover persistency. The minimum temperatures were be- generally high, the accumulated snow gave rise to effects re- low the 1991–2005 climatology for 41 days in the period lated to its load capacity, with the isolation of little residen- January–February2 2009 in Torino and for 41 days in Alessan- tial and rural settlements, several damages on the secondary dria, where for 5 consecutive days the minima were below road system due to the tree and tree branch falls, together the absolute minimum value (−10.6 ◦C). In the end, several with many public services interruptions (electric power and landslides were recorded at low altitudes. In fact, the snow

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Table 1. The heavy snowfall impacts and social relevance.

Avalanches Snow amount/loading Direct social impact – infrastructure damages – villages snowed-up (up to 10–15 gg) – road and railway system interruptions – summer settlement destroyed – services breakdowns Indirect social impact – protection forest destroyed – people involvement in snow removal – limitations in winter tourism – relevant hardships and discomfort – delay in spring/summer mountain activities

Table 2. The main criticalities of the 14–22 December 2008 snow- region due to natural causes. The Agency, trough the real fall event. time monitoring, forecasting, and surveillance of meteoro- logical events and the consequential effects on the territory Municipalities with avalanche notification 53 supports the authorities in the warning issuing (Campus et Villages snowed up 68 al., 2007). Preventive evacuations 33 During the winter 2008–2009, Arpa Piemonte provided Roads and railways interrupted 243 the essential information to open the emergency phase be- Municipality affected by power cuts 173 fore the risk became high and provided the technical support Number of power users cut off 97 000 to the emergency management. The main activities were: the Municipality with landslide notification 95 elaboration of up-date target forecasts, the snow and weather real time data delivery, the on-line Agency avalanche information system sharing, the coordination of the avalanche and damage reporting to get a regional updating framework of accumulation over the hill country, besides the snow removal critical situations, the evaluation of inspection and interven- needs and infrastructures damages, caused a rapid soil satu- tion demands in order to give priorities, the support to the ration, which fostered soil slips and debris flows. avalanche and snow pack survey and to artificial triggering, The Table 1 summarizes the impacts of the avalanches and the guideline for the local avalanche commissions definition. the snow loading that affected environment, properties and Moreover the issue of the weather product for the motorways people for a long time. to optimize the closing, cleaning and salting operations and, To get the real aspects and numbers of the emergency in above all, being at the task force disposal 24 h a day. the mountain area, we report for example the event of 14– 22 December 2008, when the intensity of the new snow was This technical support allowed analysing and highlighting up to 2 m in 36–48 h. This determined a snow accumulation the direct and induced effects of the heavy snowfalls, outlin- on the ground around 2–3 m at 2000 m of altitude, almost ing risk scenarios characterized by different space and time everywhere, doubling the mean values of the season. The scales. The risk scenarios deployment provided a prompt Table 2 reports the main criticalities total numbers during the recommendation list, both for the emergency management event and in Fig. 4 the wide territory involved is shown. and for the natural phenomena evolution surveillance plan- The damage costs to the public property caused by the 14– ning to assure the people and property safety. The Table 3 22 December 2008 snowfalls have been estimated by the Re- summarizes the different impact time scales for the moun- gione Piemonte to be about 470 millions of euros, giving ev- tain and plains area, highlighting the long last effects in the idence of the real emergency dimension of the event, never mountain and the consequent difficulties in emergency clo- occurred during the last 20 yr. A similar amount (541 mil- sure decision-making. lions of euros) was evaluated for damages caused by flood The operational implementation of the technical rules for event in Piemonte in May 2008. the snow emergency management, tested the first time during the event in a dynamic way, pointed out its drawbacks and potentiality, highlighting the “emergency preparedness” 3 The technical support to the snow emergency importance at different institutional levels, with the popula- management tion and stakeholder involvement. Some measures have to be especially underlined: the coordination of the snow monitor- The Regional Agency for Environmental Protection of Re- ing over the territory performed by the local operators and the gione Piemonte (Arpa Piemonte) is in charge of the opera- steps taken locally; the improvement of the tools for the snow tional evaluation of the impacts of extreme events over the pack evaluation to drive the avalanche artificial triggering off, www.adv-geosci.net/26/149/2011/ Adv. Geosci., 26, 149–153, 2011 152 R. Pelosini et al.: Lessons learnt from the snow emergency management

Table 3. The different impact time scales for the mountain and plain areas.

Emergency phase Post emergency phase (spring season) Post emergency phase (summer season) avalanches spring avalanches rural settlement damages road/parking/roof snow accumulation debris ﬂows ecological effects (wooded areas, animals, ecosystem services) villages cutting off enhancement of ﬂoods/discharge delay on spring/summer mountain activities (grazing) service breakdowns wood silting up tracks, signs, fences and avalanches barrier damages

mountains infrastructure damages infrastructure damages infrastructure damages forest heritage damages forest heritage damages forest heritage damages road/parking/roof snow accumulation enhancement of ﬂoods/discharge road icing service interruptions frost

hills/plains air quality worsening

Fig. 4.1 TheFigure territorial 4.distribution The territorial of the distribution damages (pink), of powerthe damages services breakdowns(pink), power (blue) se andrvices road breakdowns interruptions (yellow)(blue) and caused by the 14–22 December 2008 snowfalls. 2 road interruptions (yellow) caused by the 14-22 December 2008 snowfalls. in case3 of snow3 The mass technical hazard assessment, support and to the their snow regional emergencyMm3 management Total SWE Piedmont 5000 coordination.4 The The Regional rapid reporting Agency of for avalanches Environmental and damages Protection of Regione Piemonte (Arpa Piemonte) is in was good, as well as the management of available resources 4500 4000 for survey5 charge and counteractions. of the operational Moreover, evaluati becauseon of the the snow impacts of extreme events over the region due to natural 3500 accumulation in the mountain basins represented the biggest 6 causes. The Agency, trough the real time monitoring,3000 forecasting, and surveillance of water stock of the latest 10 yr (Fig. 5), a tool has been set up 2500 to carry7 onmeteorological several hydrological events simulations and the consequential forced by differ- effects 2000on the territory supports the authorities in the ent weather8 warning scenarios issuing to evaluate (Campus the effects et al., on 2007). the discharges 1500 in case of spring ﬂoods, according to a method described by 1000 Rabuffetti9 etDuring al. (2007). the winter 2008-2009, Arpa Piemonte provided500 the essential information to open the 0 10 emergency phase before the risk became high and provided10/1999 10/2000 the 10/2001technical 10/2002 10/2003support 10/2004 to 10/2005 the 10/2006 emergency 10/2007 10/2008 10/2009 4 Conclusions and recommendations 1 Figure 5. Snow Water Equivalent (SWE) calculated for the Piemonte Po basin area from October 11 management. The main activities were: the elaborat2 1999Fig.ion to5. February ofSnow up-date 2010. Water target Equivalent forecasts, (SWE) calculatedthe snow for and the Piemonte Po basin area from October 1999 to February 2010. The12 experience weather highlights real time the importancedata delivery, of having the on-line deﬁned Agen3 4cy Conclusions avalanche and recommendationsinformation system sharing, the and shared standards, acknowledged and accepted prevention 4 The experience highlights the importance of having defined and shared standards, acknowledged 13 coordination of the avalanche and damage reporting5 and to accepted get a prevention regional actions updating suited to minimize framework the heavy snowfall of critical effects, with particular actions suited to minimize the heavy snowfall effects, with 6 attention to the road conditions, to the school system opening/closing and to the preventive 14 situations, the evaluation of inspection and interv7 entioninformation caredemands in order to avoidin theorder missing toperception give of thepriorities, risk. Special attention the must be paid 15 support to the avalanche and snow pack survey8 andto the tohydrogeological artificial risk triggering, condition assessment, the forecasting guideline and su rveillance.for the In fact they are Adv. Geosci., 26, 149–153, 20119 enhanced by the winter heavy snowfalls and www.adv-geosci.net/26/149/2011/ show their effects during the following season. The 16 local avalanche commissions definition. Moreove10 improvementr the inissue the prediction of ofthe the riskweather evolution scenarios product and in the forprevention the action planning 11 helps the decision making to a considerable degree. 17 motorways to optimize the closing, cleaning and12 saltToing conclude, operations a short list of ge and,neral recommendations above all, for being the future casesat the is presented task here: 13 • setting up of the task force timely (actors/leadership, information flows, responsibility and 18 force disposal 24h a day. 14 role assignation, suitable venue guaranteeing data access, elaboration tools, connectivity, 19 This technical support allowed analysing and 15high lightingcomfort, externalthe directcommunication and capacity); induced effects of the 16 • involving of the local actors since the emergency declaration; 20 heavy snowfalls, outlining risk scenarios characterized17 • improvingby different of the coordination space in theand road timeand motorways scales. closing The and opening; risk 18 • providing the media, authorities and people with univocal, official and timely information;

7 9 R. Pelosini et al.: Lessons learnt from the snow emergency management 153 particular attention to the road conditions, to the school sys- References tem opening/closing and to the preventive information care in order to avoid the missing perception of the risk. Special Arpa Piemonte: Rapporto sulle piogge e nevicate intense del 14–17 attention must be paid to the hydrogeological risk condition Dicembre 2008 in Piemonte, http://www.arpa.piemonte.it/index. \ \ assessment, forecasting and surveillance. In fact they are en- php?module=ContentExpress &func=display &ceid=806, 2008. hanced by the winter heavy snowfalls and show their effects Barbero, S.: Forecasting Natural Phenomena for Emergency Man- during the following season. The improvement in the pre- agement, Evaluation and prevention of natural risks, Taylor and diction of the risk evolution scenarios and in the prevention Francis Group NL/Balkema, 9–14, 2007. action planning helps the decision making to a considerable Bosco, F., Gandini, D., Giudici, I., Marco, F., Paro, L., Tarar- degree. bra, M., and Tiranti, D.: The mass movement of the Rio Fre- To conclude, a short list of general recommendations for jus (Bardonecchia, NW Italian Alps) on 6 August 2004, Evalu- the future cases is presented here: ation and prevention of natural risks, Taylor and Francis Group NL/Balkema, 409–447, 2007. – setting up of the task force timely (actors/leadership, Cordola, M., Turroni, E., Prola, M. C., Bertea A., Zaccagnino, information flows, responsibility and role assignation, M.,Turco, M., and Martorina, S.: Piogge e nevicate intense del suitable venue guaranteeing data access, elaboration 14–17 Dicembre 2008, Neve e Valanghe, AINEVA ed., 67, 28– tools, connectivity, comfort, external communication 37, 2009. capacity); Maggioni, M., Caimi, A., Godone, D., Freppaz, M., Bertea, A., Cor- dola, M. Prola, M.C., Bertoglio, V., and Frigo, B.: The avalanche – involving of the local actors since the emergency decla- events of December 2008 in Ceresole Reale, Proceedings of the ration; International Snow Science Workshop, Davos (CH), 2009. Rabuffetti, D. and Salandin, A.: Analisi delle risorse idriche – improving of the coordination in the road and motor- immagazzinate nel manto nevoso nei bacini alpini, Neve e ways closing and opening; Valanghe, AINEVA ed., 62, 42–49, 2007. Rabuffetti, D., Salandin, A., and Cremonini, R.: Hydrological mod- – providing the media, authorities and people with univo- elling of snow cover in the large upper Po river basin: win- cal, official and timely information; ter 2004 results and validation with snow cover estimation from satellite, Geo-Environment & Landscape Evolution II, 293–302, – defining of the procedures for artificial avalanche 2006. releases, increasing the coordination with the local Regione Piemonte, Direzione OO.PP., Difesa del Suolo ed Econo- avalanches committees; mia Montana a Foreste, Settore Protezione Civile: Evento Me- teoidrologico e nivologico del 14–22 Dicembre 2008, 2008. – improving the people preparedness; Tiranti, D.: The sediment gravity flows triggering mechanisms, evolution and sedimentary processes in Western Italian Alps, Ph.D. – motivating and incentiving volunteers; Thesis, Department of Earth Sciences, University of Torino (I) – being prepared but with a flexible attitude. with advising by the Cambridge Quaternary, Department of Ge- ography, University of Cambridge (UK), 100, 2008. Acknowledgements. The authors would like to thank their col- Valt, M. and Cianfarra, P.: Lo straordinario inverno 2008–2009, leagues for continuing support and contribution during the snow Neve e Valanghe, AINEVA ed., 67, 4–15, 2009. emergency and for the report preparation.

Edited by: G. Boni Reviewed by: one anonymous referee

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