The Kulturisk Regional Risk Assessment Methodology for Water-Related Natural Hazards – Partapplication 2: to the Zurich Case Study P

Home , Albis, Friesenberg, Gewerbeschule (Zürich), Langnau am Albis, Langstrasse, Leimbach (Zürich)

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , and 4 , M. Zappa 3 , R. Olschewski 1,2 7876 7875 , A. Critto 2 , S. Torresan 1 1,2 , M. Bullo 1,2 This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Dept. Environmental Sciences, Informatics and Statistics University Ca’Foscari Venice, Centro Euro-Mediterraneo su i Cambiamenti Climatici (CMCC), Impacts on SoilSwiss and Federal Research Coast Institute WSL, Economics and Social Sciences,Swiss Birmensdorf, Federal Research Institute WSL, Mountain Hydrology and Mass Movements, Received: 9 June 2014 – Accepted: 11Correspondence June to: 2014 A. – Marcomini Published: ([email protected]) 11 July 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/7875/2014/ 11, 7875–7933, 2014 doi:10.5194/hessd-11-7875-2014 © Author(s) 2014. CC Attribution 3.0 License. 1 Venice, Italy 2 Division, Lecce, Italy 3 Switzerland 4 Birmensdorf, Switzerland A. Marcomini The KULTURisk Regional Risk Assessment methodology for water-related natural hazards – PartApplication 2: to the Zurich case study P. Ronco Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , altering ff erent geographical and socio-economic ff 7878 7877 erent receptors lying on the Sihl River valley including the city of Zurich, ff Particularly, in Switzerland severe flood events have occurred in many catchments in the last decade,have while occurred during periods the with last frequent 150 floods years (Bründl alternated et with al., quieter 2009). periods In northern Switzerland, currently being intensified by changescover, in all temperature, linked precipitation, to climate glaciers change.contribute and Projected to snow changes altering in the precipitation intensityflash regimes and floods will frequency also (IPCC, of 2012). rain-fed floodsinflicted In and Europe, by possibly floods also natural account of disasters,about for both the natural biggest on disasters share economicsource: of losses terms 2009). EM-DAT, damage and and frequency life in threat Europe (see: statistics for the period 1980–2008, impacts of flooding canet be al., dramatic 2012). and In have thisthe a sense, problems the of wide so flooding community called bywatercourses impact not-sustainable and accelerating (Mazzorana removing development and floodplain can increasing storage exacerbate surface (OPW,factors 2009). water In causes run-o the meantime, of physical floods are strongly connected to the hydrological cycle which is 1 Introduction Nowadays, one of the major environmentalglobal issues scale which is is asserting the morenatural increasing and disasters, more threat flooding at has related significant to impactspeople’s natural on lives, human disasters. activities their Among as property, the it servicesinclude can variety threaten as housing, of well transport as andindustrial the and public environment. agricultural service enterprises. Assets infrastructures, The at health, as risk social, well economic can and as environmental commercial, well as to severalits other sites flexibility across and Europecontexts, (not possible depending presented adaptation on here), data toother has hazard availability demonstrated di scenarios. and peculiarities of the sites, as well as for Finally, the application of the KR-RRA methodology to the Sihl River case study as impacted by the selected flood scenario mainly because their scattered presence. with the lower classesdeeply of urbanized risk. area In within general, andbehind higher around the to relative Zurich risks the city are Sihl centremainly concentrated and River due in areas course. to the that rely Here, highinundated just forecasted buildings population are injuries density mainly classified and and asflooded continuous potential high and roads, fatalities presence discontinuous urban are of pathways fabric; main old and train (vulnerable) station railways, people; (Hauptbahnhof), the aredamages. at majority The high of risk analysis of of themand inundation, flood causing referring cultural huge risk to indirect heritage to the have agriculture, natural pointed Zurich and out semi-natural that systems these receptors could be relatively less has been producedstudy. to By means visualize of thethe a spatial consideration tailored of pattern participative technical approach, expertsstakeholders of for the with the flood appraisal the total of risk (essential) risk therelative point specific maps within risks. scores of and supplement The view the weights total related of risk area to the maps the relevant of receptor- obtained for the Sihl River case study are associated assessed for di which represents a typicalthe case peculiarities of of rivera the flooding 300 specific in years case urban returntargets, study, area. exposed period risk to After scenario maps flood characterizing (including (selected buildings, risk have as infrastructures in been and baseline) agriculture), the developedand for natural Sihl under cultural and six semi-natural valley, heritage. identified namely: systems rank Finally, relevant people, the areas economic and total activities hotspots risk at index risk map, by which means allows of to Multi identify Criteria and Decision Analysis tools, The main objective ofAssessment (KR-RRA) the methodology, presented paper in the is companionet paper the al., (Part 1, 2014), application Ronco to ofmethodology the the to Sihl KULTURisk River the Regional valley, site-specific in Risk context Switzerland. and Through a features, tuning flood process related of risks the have been Abstract 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) entering 2 erent, more ff erent sources, ff erent components ff ects of local scale issues erent components of the ff ff ) are located at Drusberg in the 2 ). As many of the alpine rivers, the 2 erent flood impacts on multiple receptors ff 7880 7879 ective engagement of scientists, stakeholders, ective and integrated approach has been used ff ff erent prevention scenarios in the considered region. Accordingly, ff ect large geographic areas (Hunsaker et al., 1990). By means of di ff Finally, through the integration of the three pillars of risk concept defined by UNISDR On these basis, the pro-active and e separated by a chain ofin hills. the Finally, Zurich the city Sihl centre River (downstream joins basin: the 180 Limmat km River at Platzspitz 2 The Sihl River valley The Sihl is a 68The km sources long of alpine the river riverCanton (total located of basin in Schwyz coverage: the (SZ) 336 km foothills inthe the of artificial central the Sihl part Alps lake of of regulated Switzerland.the Switzerland. by Downstream Canton a it of concrete flows Zurich dam through (ZH) (upstream through basin: the 156 km Sihl valley and flowing parallel with Zurich lake, the European level. This innovative,for e assessing the riskZurich and of surrounding, flood by posed(i.e. people, considering by economic di activities, the natural and Sihlthe semi-natural meso-scale River systems, level. cultural and heritage) at tributaries to the city of risk assessment, (iv)assessment relative risk are estimation. theinfluence The on evaluation local main scale of objectives problems ason of well broader regional as regional endpoints the scale in cumulative scale e orderorder problems, to to prioritise prioritize their and the evaluate contribution risks intervention present and and in mitigation the measures. region(2005) of and IPCC interest (2012) in asmethodology hazard, represents exposure, a and benchmark vulnerability, the for proposed the KR-RRA implementation of the Floods Directive at methodology follows the theoretical approachand proposed by used Landis in and Weigers asuggested (1997) the wide following implementation range steps: ofhabitats (i) and identification cases of impacts, (Pasini the (ii) di et rankingof the al., the (relative) 2012; importance risk of Torresan assessment, et the di al., (iii) 2012), spatial that visualisation of the di a multiplicity of endpoint of regional interest (Landis, 2005). The proposed KR-RRA a multiplicity of sources of hazards, widely spread over a large area, which impact the risk posed bybeen a widely variety presented of byRegional water-related Ronco Risk hazards. Assessment et The approach, KR-RRA al.and in methodology (2014) systematic general, has way in is to the aimedthat estimate companion a at and paper, providing compare a Part theor quantitative impacts 1. of less The environmental sophisticated problems prioritization algorithms, of the targets/multiple RRA receptors/elementsof approach the and benefits provides areas of the atRRA di identification becomes risk and important and when evaluation policymakers are called to face problems caused by related natural hazards havefew been of proposed within them theThrough can scientific a be community, but tailored adopted very Regionalout to FP7-KULTURisk Risk Project implement (Knowledge-based Assessment approach (RRA) the to developprevention-KR), approach, a last developed cULTUre of the a European Risk recently state-of-the-art Flood phased risk Directive assessment (FD). methodology to assess where 56 % of this(up damage to) caused 37 % by due six to single sediment flood transport. events frompolicy 1978 and to decision makers 2005, towards the and challengingthe objective impact of reducing of and mitigating floods,science is of dramatically these needed. events, theirrobust In impacts, fact, and enough only options over for tostrategies the dealing (IPCC, with last support 2012). them few has Several years and become methodologies the develop to assess comprehensive the and risk posed mature by assessment water- onwards, while fewmassive floods flood have2007, events occurred Schmocker-Fackel in and in-between.et Naef, northern Since al. 2010). (2009) around Switzerland Recent and Badouxbillion researches 1900, et Euros have conducted of al. three total (2014) occurred by monetary in Hilker Switzerland loss (1999, due has to estimated 2005 floods, an debris approximate and flows, 8 landslides and rockfall, indeed, numerous floods were recorded between 1874 and 1881 and from 1968 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in the downstream ff are covered by forest 2 ) covers only the lower part of the 2 7882 7881 for the environs of Zürich central station are triggered ff er capacity of Sihl lake retention basin is not enough to ff are devoted to agriculture. Several cultural heritage hotspots are 2 generation in late spring and early summer. Flash-floods as triggered by ce of Canton of Zurich, 2011), while 20.19 km ff ffi (more than half of the case study area) and the total population is 289 029 2 Pro Sihltal (2008) reported the most important floods that have occurred in the Sihl The area of reference is densely populated, in particular on its lower part close to As far as the administrative characterization is concerned, the Sihl River valley The Sihl River valley is extensively wooded and, in particular, the forest lying on the registered in the areademonstrated but that since the then, bu in 2005 and in 2007, severe inundations have River valley duringflooded the Zurich last main three trainwere centuries. station badly In with damaged more and 1910, than thewere in under service 40 1 cm particular, m was of of interrupted, a water water,were Leimbach and massive some some and completely buildings railway event Adliswil of flooded. tracks districts the Swissfor In National Museum both 1937, at Platzplitz hydropower theflooding and artificial downstream as (Schwanbeck multipurpose et retention Sihl al., 2010). (over-flow) lake Until basin was 1999 no to realized more reduce floods have the been frequency of exceeds natural storage capacities in soil,of rivers, lakes the and basin, reservoirs. In thefor the which lower Sihl part it River represents flowsjoining the through largest the flood Zurich, Limmat threat Switzerland’s(Zürich (Addor River, most Hauptbahnhof et the HB) populated al., located Sihl 2011). city, in flows In the city fact, beneath centre, just the as before showed main in Fig. railway 2. station of Zurich The Sihl River basin isto flash located floods: in during the wintertimegoverns middle runo snow of accumulates Swiss in Alps theintense and headwaters thunderstorms it and is might snow particularly be melt (e.g. responsible prone the for region high of damages Einsiedeln),part but in of rarely the lead the upstream to river. areas criticalby Critical long-lasting peak-runo runo rainfall events that2013) lead This to process the overspill isof of generally water the slow input Sihl exceeds but lake the (Scherrer severe ability et floods al., of can the occur soil whenever to the absorb rate it or when the amount of water of Bühl. 3 Hydrological pattern and regime Swiss National Museum, the Kaspar Escher House, the Fraumünster and the Church Werd, Wipkingen, Wollishofen) andAlbis, 5 Rüschlikon municipalities and (Adliswil, Thalwil) Kilchberg, (see Langnau Fig. 1). am the city ofto Zurich, CORINE which Land is Cover41.28 (CLC) km located classification north (EEA, 2007), and(Statistical the north-west O residential of area covers and Zurich just lake. 7.67 According km present in the valley and especially in Zurich city centre, among the others are the includes parts of theZurich districts (lower Sihl of valley). Einsiedeln The studied (SZ)valley area and (upper (77.97 km in Sihl particular valley), the HorgenAltstetten, city (ZH) City, of Enge, and Zurich Escher with Wyss,Höngg, its Friesenberg, Langstrasse, 21 Gewerbeschule, Leimbach, districts Hard, Lindenhof, (Albisrieden, Oberstrass, Hochschule, Alt-Wiedikon, Rathaus, Sihlfeld, Unterstrass, river valley is also cultivated asSihl arable consist land of and several with small pastures. torrential(Rickenmann The rivers, upstream et able part to al., of mobilize the 2012) highcauses quantities and the of typical drift-wood bedload brown (Turowski color etof of the al., the Limmat, water 2013). drift of wood While thesince represent Sihl bedload it a (Fig. just serious can 2) treat cause that along joinbelow obstruction the the Zürich of whole clear central the channel waters station. of river the section Sihl, below bridges and, most important, not navigable. hills is classified as coniferous andbeen mixed forest. declared Since the as year (protected) 2000, thebecome Natural Sihl attractive Reserve forest for has recreation and purposes several as areas well along as the important ecological river habitats. have The Sihl preserves most of its natural morphological pattern of a meandering river and it is 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ective ff ff ected by ff ce of Canton of can be released ffi 1 − s 3 erent use of the various hazard ff erent scenarios to be investigated erent receptors could be a ff ff ce (BFS, Bundesamt für Statistik) and the 7884 7883 ffi erent stakeholders and institutions/authorities of the ce of Topography, the Statistical O ff ffi ce for Agriculture (FOAG), (Bundesamt für Landwirtschaft, BLW) in ffi . 2 erent prevention scenarios. According to the DEFRA (2006) approach, followed by the KR-RRA methodology However, while existing flood hazard maps can be easily used to estimate flood For the risk assessment to agriculture and natural and semi-natural systems, the The Sihl catchment had been comparatively little impacted by the extreme rainfall ff depth, they do provide information on flow speed very rarely (DEFRA, 2006). This is metrics depending on thedepicted analysed in Table receptors 2. in order to assess theto relative assess risk, the as riskmapped) by to commercial, more people, ordebris water less factor, sophisticated, depth that hydraulics and models. ranges Moreover, velocitydebris between the would are 0 lead and normally to 1, a computedranges significant respectively of hazard, (and low water can and depth be and high easily velocity, assigned probability as according per that to Table 3. di 4.1 Hazard data processing As explained by Roncoidentifying et the al. relevant (2014)coming physical in metrics from Part (water hydrodynamics(baseline 1, depth, models or the velocity alternative). for hazard and The assessment the methodology flood is makes di extension) di aimed at CLC dataset (EEA,spatially 2007, characterize the targets with at the spatialand regional level; cultural resolution while for heritage, buildings, of infrastructures databeen 1 with : used. 100000) a Finally, finer to hasprovided resolution characterize has been (spatial the been used resolution used receptor25 to m of to people, compute 1 the : the 5000) residential number has census of data people within residential cells of the (flood) hazard. Theof data Zurich, has the been Swiss mainlyZurich, Federal provided the O by Swiss theSwiss GIS Federal Federal Centre Statistical O of O Canton raster, vector graphic or numerical format, as specified in Table 1. assessment, that is the degree to which the di heritage) in order topercentage perform of the exposure disable assessment, people, (iii) relevant slope, indicators soil (e.g. type etc.) to perform the vulnerability 4 Dataset characterization and processing The dataset requiredcharacterization for of the the applicationinto intensity specific of and hazard the the scenarioflood frequency KR-RRA (e.g. extension, of hazard methodology return the metrics period), includes: suchreceptors flood (ii) (e.g. (i) as event, people, spatial flow to economic pattern velocity, activities, be water and natural depth, framed distribution and of semi-natural systems, the cultural investigated area. The complexity ofa hydrological planned pattern strategy of of theapproach prevention in Sihl measures order River dramatically to assess asks valley the and fortools risk to a of the identify flood broader need to and integrated multiple for prioritize receptorsdi areas and and a suite targets of at e risk to finally evaluate the benefits of of August 2005event (Bezzola triggered and a (preliminary) Hegg,et flood 2007; al., risk 2007) Jaun assessment and,prevention of et measures. finally, the However al., to the catchment date, 2008, planning out (Schwanbeck system of of see the (EWS) few planned Fig. model ones, immediate, only to 2)implemented, intermediate the forecast early but while and extreme warning intermediate long-term this events andanalysis and and mitigate long-term discussion their by prevention impact the measures di has are been still under even if thethe discharge catchment of area upstream thein of Sihl case the is dam of are relatively heavyemergency usually precipitations regulations modest diverged procedures, dam into and discharges overflow the as most mightinto high lake the occur as of of Sihl 470 and, Zurich, m River, the with according waters dramatic to consequences from the downstream (Addor, dam 2009). mitigate the impacts of extreme flood events during heavy rainfalls seasons. In fact, 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | for class 1 1 − s ect the typical ff 2 0.5 m = d · v product have been selected for are associated to the highest level d · v v ering capacity of the Sihl lake, the EWS ff are known as single values, and not as and ect the main railway station of Zurich, that d ff d 7886 7885 and velocity 100 years – medium probability of floods, < d 300 years – low probability of floods. < TR product and < TR d erent classes of frequency of the event (high, medium and < · 30 years – high probability of floods, ff v < 0.5 m for the class 2 of Table 4, and = d erent flood scenarios (baseline and alternative) where structural and/or ff average event 30 years rare event 100 years frequent event TR – – – The Canton of Zurich is currently discussing further prevention measures such as In 2008 an Early Warning System (EWS IFKIS Hydro Sihl) has been installed As request by the European Flood Directive (2007/60/EC), the baseline scenarios The pattern of water velocity has been calculated as follow. Based on a precautionary Zürich to both allow for increased hydropower production and accelerated drawdown retention system by extending the reservoircontributes bu to a consistent reductionin of flood this risk study magnitude the ofthis baseline the Sihl scenario mitigation River. considers However, measure the sinceassessed situation the before to the reduction a establishment of of reliable(yet) available the degree (Addor, flood 2011). because risk data for referring the to EWS largerbypass cannot tunnel flood be (close events to are Langnauvalley am not into Albis, the Fig. 1) Lake diverging of flood Zürich, peaks along or the a Sihl larger pipe between the Sihl lake and the lake of along the SihlIFKIS River is valley a (Romangforecasts hydro-meteorological provided ensemble by et the prediction (deterministic) al., model systemCOSMO-LEPS. COSMO-7 2011; and based It the (probabilistic) propagates on Bruen model the atmospheric ensembles et atmospheric from al., COSMO-LEPS, uncertainty leading 2010). by a ingesting The probability atmospheric of EWS errors. Coupled with a flood has been consideredsince the the most other relevantprone two area for scenarios of the (30 thetypically purpose Sihl and valley is 100 of and a years) this docatastrophic only not very study configuration, a marginally critical (see the a hot Fig. selectedplan spot (baseline) the 3) in mitigation, scenario case adaptive,framework. gives response of the and opportunity flood. preparedness to Finally, actions by in assessing a the conservative most authorities and land planners toand characterize the properly hazard in manage theconcerned, the area, prepare the events for floods available (EEA,(30, flood 2009). 100 hazard As and 300 maps farCanton of years as referring Zurich. of The the to low return Zurich probability three period) – case classes high have intensity study been of 300 is provided years hazards return by period the scenario GIS Centre of Spatially distributed flood hazard maps are normally used by property owners, local non-structural solutions to mitigate, and possibly reduce, the risk areshould planned. be basedclassified on according deterministic to flood di low). hazard In maps, particular, wherehazardous flood-prone the event and areas probability the are classification depends is based on on the the following concept thresholds: of return period of the 5 Baseline and alternative hazard scenarios The KULTURisk methodologicalanalysis of framework di requires the preliminary setting and principle (highest values ofof depth hazard) theeach highest class values (e.g: for depth of Table 5). Moreover, dueclasses to 2 the and specific 3Now, range of of provided intensity values that have refereed the beena to merged range the of as case values well study, Table as as 6). it classes was 6 before, and it was 7 easy of to depth. derive the pattern of velocities (see available. In fact, onlythe hazard combination maps between water with depths waterbeen and depth velocities) provided, grouped and without in any intensity range explicit ofbeen patterns specification values used (namely: about have to the get particular them (see models Tables that 4 have and 5). the case of the Sihl River valley, where patterns of flow velocities were not directly 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 2 − erent ff with 30 148 2 er from the higher ff 7888 7887 respectively). Most of the upper part of the Sihl 2 − ) spatially distributed along the Sihl River valley. As ected areas, Albisrieden and Altstetten districts that are 2 ering capacity of the Sihl lake during critical flood events. ff ce of Canton of Zurich has provided demographic data ff R ffi erences among the SF score actually depend only on the ff ) and fatalities ( 1 R As far as the exposure assessment is concerned, the total population living in not negligible, if weresidential consider area. the high density of population that actually rely on the densely populated with mediumof casualties scores with for 223 suscetibility, andunderlined are that 155 these subject injuries two of and districtsof 5 are higher the normally fatalities values Sihl. flooded each, Considering by respectively. only the It thenumbers Limmat should Sihl of River, prone-area, casualties a be the are tributary Adliswill, districts Alt-Wiedikon, thatof Langstrasse su and injuries Sihlfeld with between a range 55considering the to total population 96 of andpeople the study 2 is area to is 0.01 0.35 %. 3 % and These fatalities. the The percentage rates of percentage suggest dead of that injured risk people to people is generally low, despite People related riskinjuries maps ( (Figs. 4for and the 5, otherobtained Tables receptors, through 8 the the andof equal-interval intervals 9) total classification injuries provide of is methods.estimated the values estimated in The number 29. in provided Among forecasted 1000, of the by number while a chromatic the number tables of are total (potential) fatalities is area ranges from 7.6has been to used 32.3 to %.residential estimate Finally, areas. the The the number normalization presence phase of hasprocedure, people of been so within performed people according cells the the within of number KR-RRA people each 25 of m relative injured/dead district resolution to people the in has district the with been highest divided population. by6.1.2 the number of Results of people toresidents characterize the with susceptibility disabilities).district, factors assuming The (people that same aged fordistributed. each more value municipalities Therefore, than the di (5 %) number 75percentage of and has disable of people been residents is aged equally considered 75 for years each or over. The SF computed within the study Moreover, the Statistical O (11 759 and 13 163Valley habitants km has a lower density, with a range between 826 and 5981 habitants km 6.1.1 Assessment According to the KR-RRA proceduredata (see processing the Part presented 1, above,been Eq. the calculated 1) and and hazard reported following scores in theincreasing Table (hazard) 7. for values The Sihl mean hazard an River scores increasing range case hazard from for 0.9 study people. to have 6, where residential areas is ofhabitants), 289 029. while The Sihlfeld largest and district Gewerbeschule is Altstetten are (7.48 the km most densely populated ones assessments, GIS based maps andhave related been statistics produced of and total presented and below. receptor-related risks 6.1 Risk to people 6 Results of the KR-RRA applicationThe to the KR-RRA selected receptors methodologyapplied presented to inat the the companion risk, Zurich paperand case namely: (Part agriculture; study people; 1) naturalthe has by economic and sub-sequential been considering semi-natural implementation activities, of systems the including the and whole buildings, hazard, cultural suite exposure, infrastructures heritage. susceptibility of Through and receptors risk Furthermore a reservoir for drifttoo wood (Fig. is 1). thought In of case toflood of be risk being realized of established, in the these Langnau Sihl am preventionprevention measures Albis, to measures could a have reduce lower not the levelhave yet but not details been been on estimated. considered the in Due expected this to impact study. under this, di alternative scenarios of the lake to increase the bu 5 5 25 20 10 15 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent classes of risk. ). Moreover, coupling 2 ff erent use of buildings. ff erent CLC classes. ff 7890 7889 erent uses; the related normalization phase for ff ected by the flood event would be only inundated ff . The percentage of flooded buildings is around 17 % while the 2 er from dramatic structural damages. Despite this, the flooding can ff erent uses (i.e. residential, commercial and industrial areas). Table 10 ff As already mentioned, the studied area is mostly classified as residential one and As already reported by the companion paper (Part 1), the vulnerability assessment As already mentioned, in fact, the KR-RRA methodology considers people living in relevant data for the analysed receptor, considering the di rail networks andIn associated particular, land, only greenservices 17 (road, items urban rail are areas networksis classified and and very as associated relevant sport infrastructures (most land leisure ofmain related class) them railway facilities). to so are station the the linked of to riskthe supply Zurich the districts for city, of strategic Zurich this with transportation Hauptbahnhof). category higher networkSeveral Box number small of A of the residential of inundated areas Fig. buildingsnamely would 6 around be Leimbach, focuses the flooded on Adliswil, also Zurich in city Thalwil the centre. and southern part Langnau of am the Albis. city, Table 12 presents the percentage of flooded areasbuildings. is almost 20 % over the total surface actuallyalmost covered 95 by % of floodedand buildings discontinuous belong urban fabric) to while classto just 1.1.1 less classes and than 1.1.2 1.2.1, 6 % of of 1.2.2, CLC inundated (Continuous 1.4.1 buildings belong and 1.4.2 (industrial or commercial units, road and The GIS-based riskbuilding map across (Fig. thefixed studied 6) threshold, area. points all Being the outand the buildings would the a intensity not spatial su ofstill phenomena distribution have dramatic consequences lower of on than theimportance, the infrastructure the because such many risk as assets electricity of to and primary lower water ground services, level. heating, The are total normally numberarea located of at at buildings the at risk risk is is 2.2 3267 km and the related surface buildings has been developed0 (no by risk) considering to normalized 1 (maximum scores risk) where are6.2.2 assigned values according from to the Results di of flooded buildings referring to di structure. Therefore, the susceptibilityFinally, the risk of assessment buildings to buildings is estimates the assumed number, surface as and percentage a constant value. Building footprint) for thebuildings: spatial 19 430; localization total ofthese surface the covered data buildings by at buildings: withbelonging risk 10.67 to km the (total di number hazardshows of maps, the it statisticspotentially related is be flooded, to possible according to the to the presence di discriminate andassumes flooded coverage that, of building at buildings the which meso-scale level, can the buildings are characterized by the same 6.2.1 Assessment Floods have atotal potential damage massive to impact thepopulated on area structures, as buildings damage it is infrastructures to for mostuse the (e.g. of of the indoor partial Sihl the River goods), valley. or The Building particularly analysis makes footprint in considerable GIS densely shapefile (GIS Centre of Canton of Zurich TLM3D methodology is somehow underestimating theareas number of while injuries and overestimating fatalities injuriesworth in these and to fatalities notice inadaptive that the capacity the residential since RRA areas. these(SERRA) methodology It of aspects the is does are complete finally KR modelled not methodology in consider (see the Giupponi people’s et6.2 social-economic coping al., clusters 2014). and Risk to economic activities: buildings residential areas only, and doessuch not as include people commercial, eventuallydoes present industrial not in other and discriminate zones, are agricultural between day/night areas. usually times. Moreover, locatedcentres, During the facilities in the (as methodology their the daytime, main in working station fact, places of people Zurich) and/or and in along the restaurants, streets. bars, Therefore the shopping 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent categories of infrastructures ff ected by the flood event, belonging to the ff 7892 7891 erent level of service that the di ff main train station), see Fig. 8, pathways at Platzspitz green area, see Fig. 8, part of Zurich main train station HauptbahnhofZurich (HB), City see centre Fig. area 8, with itsdistricts pedestrian including and urban Bahnhofbrücke road and in Walchebrücke Langstrasse (two and City bridges next to Zurich – – – ected by a flood event of 300 years return period. The total extent of road, railways Considering the pattern of the urban mobility within the studied area, the following The infrastructures receptor is very relevant for the city of Zurich if we consider that As far as the spatial distribution of the (relative) risk is concerned, the Langstrasse The flood hazard assessment to infrastructures considers the flood extension as ff and to rank theservices di could provide. items could be considered the most critical hotspots points: 17 km of floodedmost of items) the the onesMoreover, railway belonging several lines to pathways the could alongflooding main of be the pathways station is completely less Sihl of relevant than Zurichconsidering flooded, River the the city one could as of economic in highway be impact. well and Langstrasse railways, Therefore especially stricken. as district. it by Of is particularly course, important the to discriminate respectively. Moreover, the roads/railway networkand of Rathaus districts Escher do Wyss, not Unterstrass, experience Hard any loss ofthe services do Sihl to River flood. flowsjust underneath beside the of main the stationalong river and the course. many For Sihl railways example, River lines thearea for are of Sihltal around the located road Sihl 16 km (Sihltalstrasse) Riverthe valley that connecting where Sihlbrugg runs the the small Sihlwald city village. (Sihl of Again, forest Zurich natural within area) the with ends district the reaching of southern Langnau am Albis (with almost 54 km refers to railways network and 155 km to roadsand and Albisrieden pathways. districtsvery are high the class most and1. high a class The of extent risk, of according inundated to the infrastructures classification has provided been by Part computed in 32 km and 26 km, rely on the study area (less than 14 % of infrastructures are at risk). In particular, around and pathways at risk is around 209 km out of 1540 km of infrastructures that currently have been considered relevantto since connect many rural of area themRiver. to are the normally city used centre, running by along pedestrian the flood6.3.2 prone area of Results the Sihl The infrastructures relateda risk map (Fig. 7) identifies the infrastructures potentially relevant flood metric; no otherbecause the flood analysis metrics is (e.g.infrastructures, not flow oriented but velocity) have rather to been the to considered assessment evaluation the of characterization step direct of structural focuses the damagesrailways loss on and for of pathways. the All service. these The spatiallinear objects exposure could extension localization be (length) geometrically and and characterized distribution by by their their of extension the (area). roads, In particular, pathway routes includes the characterization of roads, pathwaysZurich and railway main lines within train the study stationrailway area. represents network an important systemsystems: and as more strategic well than hub forIn 1900 as fact, the trains urban for Cantonal commuter daily rail theGeneva, pass-by networks Basel, are Swiss the Bern, focused Lausanne on Hauptbahnhof and and the Neuchatel. mainin country’s European Strategic and major train highways cities: out and railways station. Zurich, Zurich roads network also city. run 6.3.1 Assessment The strategic networkrailways of shapefiles, provided infrastructures by the have GIS been Centre identified of Canton using of the Zurich. The roads information and 6.3 Risk to economic activities: infrastructures 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 , CLC 2 , the risk for 1 . The valley is belongs to the − 2 2 erent classes of the CLC ff to the pastures class (class 2 7894 7893 , most of it classified as arable land. Since none 2 erent kind of forest systems: coniferous forest (0.21 km ff (around 8 % of the total agricultural area). Out of this, 0.53 km 2 railway lines at Langnau-Gattikon train station in LangnauSihltalstrasse am Albis in district, someparticular spots in Adliswil, where Leimbach and the Langnau am roads Albis runs districts. next to the Sihl River, in – – However, the area of the Sihl River valley is mainly devoted to residential and The total surface at risk is probably underestimated because the exposure As a sake of simplification and according to the overall scope of the analysis, used to identify and characterizerisk the of natural flood and along semi-natural thecharacterized Sihl systems by River exposed valley, two to that di account the forclass more 3.1.2) than which 20 covers km the areaCLC only for class very small 3.1.3) part, which andarea. mixed occupied forest The (19.98 most km intrinsic ofthat characteristics the influence of natural the environment the degreeaccording in of territory, to the impact namely the case scores of the suggested study the by (susceptibility) flood the factors to companion paper the (Part receptor, 1) have contribution. been assessed 6.5.1 Assessment Flood extension has beennatural used systems. to As characterize for the the hazard other for receptors, the the natural CLC and classification semi- dataset has been classification have been performedmissed according out to the somecultivation. CLC small resolution agricultural that could areas have thatcommercial might purposes, therefore be the agriculture importantother can receptors be such for considered as less cash people, important buildings crop than and infrastructures. 6.5 Risk to natural and semi-natural systems the pattern of flowthe velocity agricultural is above cluster the is0.59 km minimum very threshold limited: of 0.25 thenon-irrigated m s arable flooded land agricultural class area (class2.3.1) (Table 2.1.1) only 15). and The amounts 0.07 districts km to more stricken are Albisrieden and Leimbach. The agriculture relatedprocedure and risk features of map analysis introduced (Fig. above. It 9) is worth has to notice been that despite elaborated according to the namely a risk assessment attypologies in regional the scale, Sihl it River valley hastherefore, have similar been the growing same assumed pattern susceptibility that (low score. growing thetechnical plants) According agricultural evaluation and, to of Torresan the et authors, al. thebeen (2012) two considered and CLC similar to classes to of the the agriculturalto class typologies of flood) have poor with vegetation a and score meadow equal (more to susceptible 1. 6.4.2 Results of the agricultural typologiespresent mentioned in in the Sihl the valley companion (namely:has vegetables, paper been vineyards, fruit assumed (Part trees that 1) and arablewith are olive lands similar groves), actually and it thresholds. pastures should be classified as vegetables, 6.4.1 Assessment As already reportedstep by Ronco requires et the al.metrics, while identification (2014) the in exposure of assessment Parttypologies to water agriculture present 1, allows in depth the to the identify Sihl flood anddataset the River (class hazard agricultural valley flow 2.1.1 according assessment as to velocity Non the irrigatedarea di as arable devoted land to and relevant agriculture class is 2.3.1 flood 7.67 as km Pastures). The total 6.4 Risk to economic activities: agriculture 5 5 20 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff erent confessional ff erent receptor-related risks by ff 7896 7895 ) belongs to the high class of risk while the rest (around 2 ected by loss of ecosystem service caused by a 300 years return ff ) belongs to the very high class of risk. erent susceptibility factors and in particular to the impermeable ground 2 , 1.4 % of total forest areas) and two classes of risk have been identified: ff 2 erent unit of measurement (Zabeo et al., 2011; Giupponi et al., 2013). Within ff Even if the flooded surface belongs mostly to the very high class of risk, due In this sense, the ecological, recreational and economic functionalities of the Sihl a better and more detailed visualization of the spatial variability of the total risk. between 0 and 1 and,by therefore, di to allow comparison amongthis (relative) study, risks for people, expressed infrastructuresdeveloped and at cultural CLC heritage polygon the sizenatural normalisation systems level. has the For been normalization buildings, agriculture hasand been and performed scores, natural according and as to semi- semi-natural the follow: relative systems: flooded tables 1 buildings: forrisk. 0.2, the Normalised destroyed very risks agricultural: has high been 1; class assigned of natural to risk and raster and cells 0.8 of for 25 m the resolution high that class allow of The total riskmeans index of MCDA is methods that calculatedwithin allow identifying the by and studied aggregating ranking area. areas Prior di receptor and to is hotspots performed this, at to risk, a rescale normalization the process receptor-related for risk each scores of into the a numerical analysed scale cultural protection level (regional and cantonal). Asmuseum already is reported, the at Swiss national (number risk of of inundated objects inundation between 10of while and Zurich the 15) city) are and districts Langstrasse Langnau (close belonging am to city Albis to centre (along higher the lower class Sihl of valley). 7 risk Total risk index 7.1 Weighing process The cultural heritage relatedcultural risk assets map which are is supposedscenario. shown to in As be Fig. flooded a 11: inof it the result, the identifies framework 40 of the total the number items number investigated of within could the be area inundated, (416 corresponding items). to These the assets 9.13 belongs % to di 6.6.2 Results building), the Opernhaus, several ancientas well residential as buildings along and the villas Zurich in lake the etc. centre 6.6.1 Assessment The hazard assessmentflooded step consists area. in Moreover,cultural the the heritage spatial assets exposure in characterization assessment theare (extent) case present, requires of study mainly area. the classified the In asbuildings Sihl localisation ancient such River buildings. as valley, of 416 They Fraumuster, Grossmunster cultural include the the and assets di the Swiss Synagogue National in Museum, Zurich the city centre, central library of Zurich, the Rathaus (the municipal the hilly part of the area and this reducesvalley their forest susceptibility. ecosystem is not compromised by a flood6.6 event of such magnitude. Risk to cultural heritage a very small289 part 000 m (625 m to the di characteristics of thecan area be and considered asecosystems, degrees whiles not of growing relevant. along slope, In riversseasonal they the fact, flooding. are forests In very risk are addition, well related adapted in generally to the to stable occasional Sihl and and this valley resilient most receptor of the forests are located along The natural and semi-naturalarea systems related potentially risk a mapperiod (Fig. flood 10) event. allows As to(0.29 identify a km the result, only a limited portion of forest is at risk of inundation 6.5.2 Results 5 5 20 15 10 20 25 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and the total 2 7898 7897 and 0.24, that represents the lower class of risk 5 ectiveness (Yosie and Herbst, 1998). In this study, − ff 10 × The people receptor has scored 0.4, less than the one assigned to buildings and The lowest weights have been assigned to relatively less important receptors: The proposed MCDA method of aggregation is the weighted average which the receptor of importance, is higher in areas close to the main station of Zurich, where classification, normally tunedthe within calculated the range. The 0–1 mapalong range, specifically the has identifies Sihl the River been valley. hotspots Langstrasse re-tunedrelative district and and highest the according part values areas of to of at the risk; risk and city areas of Friesenberg within Zurich present the that the districts relyrisk of levels. next Werd, Areas Sihlfeld, to Alt-Wiedikon within thewell. Albisrieden Despite Sihl district being River are very courseplausible characterized because dependent by also they on demonstrate relative present that weights high the relative assigned, overall risk risk higher the as for the results study are area, considering very much The total riskwithin map the shows Sihl the River valleyrisk spatial (Fig. index pattern 12). ranges The between of total 0.6 considering flood surface the at risk classification risk within is scoresthe 7.98 the presented km relative in analysed distribution Part area of 1. In risk order belonging to to better these visualize classes, the green to red colour to flooded infrastructures andloss buildings of result services they also provide. In inentails particular, very the wide inundation high of loss (indirect) the Zurich of costsboth main for train for services station public the since transport connections it(a for represents the big whole a shopping Canton very and centrea for important area lot commercial and is reasons of residents nodal located and location in tourists). and around7.2 the train station, Results frequented and by discussion area and, inshould the be meantime, a underestimated kindweights the of have “compensation” risk been in to the assignedbeen others computation to considered area, of buildings the the therefore (0.6)Zurich most total there city. and Considering risk relevant the infrastructures index. receptors specific Higher (0.8) characteristics for of the which the study socio-economic have area, context damages related of the sense, they argued that the methodology overestimated the risk to people in residential in that district, particularly during the day time and the weekend evenings. In this it. to infrastructures, andargument this that choice has been hasbaseline used scenario raised to does not a support consider the this not-boundedimpact role assignation to played discussion. by is the the The the EWS population inthe fact main living mitigating methodology that the in only (flood) the the focuses on selected studieddo the area. to citizens Moreover, consider actually it the living number in hasor of the been people residential at argued normally area, the that and present, for main example, shopping at the area, main which station exceeds by far the number of actual residents assets have been alreadyadditional, considered cultural, in value the has buildingsA been weight analysis, added of and 0.2 to therefore has theto just been particular assigned an be to building relevant agriculture under becauseareas for protection. this are the sector not is socio-economic of not particular considered context quality of and the do not valley: have the any valuable flooded cash agricultural crops relying on the weighting process haswith been several implemented local experts during involved a inresults roundtable-meeting the and project. organized this They could were have influenced awareassigned their of weights opinion some are during preliminary as the per weights Table assignation. 16. The natural and semi-natural systemsconsidered have as scored 0 stable because,flood and as events. very stated A resilient above, weight they ecosystems of are without 0.1 has consistent been impact assigned from to cultural heritage because these considers overlapping receptors’ risksupposed to to give be numerical priority linearlyare to considered additive. those as The whose burdensome. ranking floodingmaking In damaging process process this consequences and is sense, the weightinga involvement is fundamental of a prerequisite relevant for typical stakeholders its political and e decision experts is seen as 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7900 7899 ected by a particular flood event than others, but it is highly ff erent geographical and socio-economic contexts, depending on data availability and The receptor-related risk maps, as main outputs of the KR-RRA methodology, have Together with the presented one, the KR-RRA methodology has been successfully The total risk index represents an useful indicator which allows the visualization (total Moreover, it is worth to notice that the final risk index aggregates scores coming It is important to underline that the application of the KULTURisk methodology at the ff tool able to coordinate information coming from deterministic as well as probabilistic finer data about land cover). proven to be a verythe useful support tool of for the the decision(when risk making evaluation process based in for on appropriate the risk studiedarguable prevention, management area for protection practices as the and well methodology asthe preparedness for that involvement concepts). has of Despite been relevantthe being local followed application for experts exercise. Finally, the improved the paper themethodology, assignation which demonstrated consistency has of the proven and relevance weights, to of be relevance the a of comprehensive KR-RRA and integrated risk assessment period scenarios). Into this evaluate sense, river thenational methodology flood level can impacts including be at morearea easily a than by up-scaled broader focusing one in region/national/sub onfor river order the impacts national basin) characterization on scale of or exposure a can (i.e. and very vulnerability be (i.e. local detailed finer scale Digital on Elevation by Model, a using smaller more detailed datasets with the lowerdistricts, classes in of the urban risk, areaSihl while around River the course. the city centre relative and risk areas that is rely higher justapplied behind in to to a Zurich the wide citywhich range centre of have cases contributed studiesdi across in Europe demonstrating (notpeculiarities presented its of in the flexibility site, this as work) and well as possible for other adaptation hazard scenarios to (i.e. other relevant return of flood hazard to selecteda receptors, tailored have participative been developed. approach Byto of means be relevant of applied local MCDA, for with expertsidentification each that of receptor, hot suggested the spots the total andrisk weights risk area pattern. at maps The risk have total as been risk well produced maps as allowing obtained the the for spatial the characterization Sihl of River the case study are associated Relative risk maps (GIS based) and related statistics, specifically referring to the impact been applied in order to assessyears the risk return of period flood for hazard the river scenario, valley represented the by a be 300 considered the most conservative one. The study addressed the(RRA) application methodology of for athe state-of-the-art flood Sihl Regional risk River Risk valley assessment Assessment methodology, around to developed the within city a of the veryintroduced Zurich, KULTURisk-FP7 in in site-specific (KR) the Switzerland. companion Project case, paper Thenamely for namely Part complete the 1, flood KR-RRA followed hazards, risks four subsequent exposure,paper and levels vulnerability described of the and analysis, tuning risk process assessments. as well In as particular, the the implementation procedure that has A correct interpretation ofpotential these prevention factors measures is thathot particularly could spot relevant be areas for (Torresan suitable et the for al., analysis 2012). reducing of the the risk for current 8 Conclusions more specific information are available. risk map) of areas moredependent a from receptor related risk analysis and weighting process. from multiple heterogeneous parameters.therefore The consider final not decision-makingcontributed only process in the should determining final that values value of (i.e. the susceptibility index, indicators, but hazard also metrics). the factors that the left side area of the Sihl River before itmeso-scale provides join a the screening Limmat analysis River, thatof notably allows at the targets risk. assessment and and prioritization analysis areas (at the at micro-scale) could risks be required in in the the areas considered considered at risk region. or where However, a more detailed lot of infrastructures and railway lines and buildings would be possibly flooded, and on 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . , ce ffi ce of the ffi , 2009. www.kulturisk.eu erent elements at risk, 10.5194/nhess-12-3571- ff 10.5194/nhess-14-279-2014 , 2011. 10.5194/nhess-9-913-2009 , 2009. 7902 7901 airs, Wallingford, UK, March 2006. ff , 2008. 10.5194/hess-15-2327-2011 This work was found by the Seventh Framework Programme (FP7) of the 10.5194/nhess-9-801-2009 ce of Public Work: The Planning System and Flood Risk Management, Guidelines for ffi , 2012. 10.5194/nhess-8-281-2008 impact assessment inregional Veneto risk assessment, and Sci. Total Friuli Environ., 440, Plain 219–235, groundwater. 2012. Part II: A spatially resolved Planning Authorities, Environment, Heritage and Local Government, Dublin, Ireland, 2009. Model, CRC Press, Boca Raton, FL, USA, 2005. and comparative ecological risk assessment, Hum. Ecol. Risk Assess.,assessment, 3, 287–297, Nat. 1997. Hazards2012 Earth Syst. Sci., 12, 3571–3587, doi: 2005 floods indoi: the upper Rhine catchment, Nat. Hazards Earth Syst. Sci., 8, 281–291, Gardner, R. H.: Assessing332, ecological 1990. risk on a regional scale, Environ.and Manage., Disasters 14, to 325– Advance ClimateI Change and Adaptation, a II SpecialCambridge, of Report UK, of the New Working Intergovernmental York, Groups NY, USA, Panel 582 on pp., 2012. Climate Change, Cambridge University Press, Environment, Food and Rural A of water relatedDisasters, disasters. edited The by: Paron, SERRA P. and Approach, Di Baldassarre, in: G., Hydro-Meteorological Elsevier,2007, in Hazards Nat. press, Hazards and 2014. Earth Syst. Sci., 9, 913–925, doi: European Union, Luxembourg, 2007. Adaptation in River Basin Management Plans,of EEA/ADS/06/001 the – European Water, Union, Publications O Luxembourg, 2009. Visualising flood forecasting uncertainty: someWorking current Group European EPS 3, platforms Atmos. – Sci. COST731 Lett., 2, 92–99, 2010. application in natural hazard risk9, management 801–813, in doi: Switzerland, Nat. Hazards Earth Syst. Sci., erste Einordnung, Bundesamt für UmweltWSL, BAFU, Umwelt-Wissen, Zurich, 707, Eidgenossische 215 Forschungsanstalt pp., 2007. system for the citySyst. of Sci., Zurich 15, 2327–2347, (Switzerland): doi: skill, case studies andin scenarios, Switzerland, Nat. Hydrol. Hazards Earth Earth Syst.2014. Sci., 14, 279–294, doi: exposure and vulnerability, in order toas evaluate required flood by risks the for European di Floods Directive. flood forecasting and to integrate the multi-faceted physical/environmental aspects of Pro Sihltal: Lebensraum Sihl, Druckerei Studer AG, Horgen Adliswil, Jahrheft Nr. 58/2008. Pasini, S., Torresan, S., Rizzi, J., Zabeo, A., Critto, A., and Marcomini, A.: Climate change OPW, O Landis, W. G. and Wiegers, J. A.: Design considerations and aMazzorana, suggested approach for B., regional Levaggi, L., Keiler, M., and Fuchs, S.: Towards dynamics in flood risk Landis, W. G. (Ed.): Regional Scale Ecological Risk Assessment. Using the Relative Risk Jaun, S., Ahrens, B., Walser, A., Ewen, T., and Schär, C.: A probabilistic view on the August IPCC, Intergovernmental Panel on Climate Change: Managing the Risks of Extreme Events Hunsaker, C. T., Graham, R. L., Suter II, G. W., O’Neill, R. V., Barnthouse, L. W., and DEFRA: Flood Risk to people Phase 2, FD2321/TR2 Guidance Document, Department for Hilker, N., Badoux, A., and Hegg, C.: The Swiss flood and landslide damage database 1972– Giupponi, C., Mojtahed, V., Gain, A. K., Biscaro, C., and Balbi, S.: Integrated risk assessment EEA, European Environment Agency: CLC2006 technical guidelines, Publications O EEA, European Environment Agency: Report on Good Practice Measures for Climate Change Bründl, M., Romang, H. E., Bischof, N., and Rheinberger, C. M.: The risk concept and its Bruen, M., Krahe, P., Zappa, M., Olsson, J., Vehvilainen, B., Kok, K., and Daamen, K.: Badoux, A., Andres, N., and Turowski, J. M.: Damage costs due to bedload transport processes Bezzola, G. and Hegg, C.: Ereignisanalyse Hochwasser 2005, Teil 1 – Prozesse, Schaden und a culture of risk prevention (KULTURisk)”, FP7-ENV-2010, Project 265280; Addor, N., Jaun, S., Fundel, F., and Zappa, M.: An operational hydrological ensemble prediction Acknowledgements. European Commission within the collaborative project “Knowledge-based approach to develop administration of the Canton of Zürich. References IFKIS Hydro Sihl (Addor et al., 2011) and the work of M. Zappa has been financed through the 5 5 30 25 20 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2013. . ce for Disaster Risk Reduction, Geneva, 2005. ffi 7903 7904 , 2014. 10.5194/esurf-1-1-2013 10.5194/hessd-11-7827-2014 Communities to Disasters, United Nations O http://www.nat-hazards-earth-syst-sci.net/12/2347/2012/ distribution of coarse particulateEarth organic matter Surf. Dynam., exported 1, from 1–11, an doi: Alpine headwater stream, Derived from Process-Based Modelling toin Assist a Flood Pre-Alpine Risk Flash Minimising Flood ReservoirMay Prone Operation 2010, Catchment, EGU2010-4432-1, EGU 2010. General Assembly, Vienna, Austria, 2–7 climate change hazards at theHazards regional Earth scale: Syst. the Sci., case 12, study 2347–2368, of 2012, the North Adriatic Sea, Nat. assessment for contaminated sites, Part 1:analysis, Vulnerability Environ. assessment Int., by 37, multicriteria 1295–1306, decision 2011. Switzerland since 1850, J. Hydrol., 381, 1–8, 2010. Abschätzung von ExtremhochwassernTech. Report, im Geographisches Einzugsgebiet Institutpp., der der under Universität Sihl, Bern commission and Projektschlussbericht, Zürich, of TK 2007. the Consult Department AG, Zürich, of 42 Waste, Water, Energy and Air of Canton of making. An Evaluation of LessonsWashington, Learned, 1998. Key Issues, and Future Challenges, Ruder Finn, Sihlsees bis Zürich, Zurich, Bericht 12/159, 2013. Rhyner, J.: IFKIS-Hydro – earlyNat. warning Hazards, and 56, information 509–527, system 2011. for floods and debrisThe flows, KULTURisk Regional Risk– Assessment Part methodology 1: for water-related Physical-environmental7874, assessment, natural doi: Hydrol. hazards Earth Syst. Sci. Discuss., 11, 7827– measurements at the ErlenbachEarth stream Surf. Proc. with Land., geophones 37, and 1000–1011, 2012. automated basket samplers, UNISDR: Hyogo Framework for Action 2005–2015: Building the Resilience of Nations and Turowski, J. M., Badoux, A., Bunte, K., Rickli, C., Federspiel, N., and Jochner, M.: The mass Torresan, S., Critto, A., Rizzi, J., and Marcomini, A.: Assessment of coastal vulnerability to Schwanbeck, J., Viviroli, D., Weingartner, R., Röser, I., and Trösch, J.: A Statistical Model Zabeo, A., Pizzol, L., Agostini, P., Critto, A., Giove, S., and Marcomini, A.: Regional risk Schwanbeck, J., Viviroli, D., Weingartner, R., Röser, I., and Trosch, J.: Prozessbasierte Yosie, T. 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M., Fritschi, B., Klaiber, A., Ludwig, A., Bedload transport 5 5 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2013 , 2013, a a TLM3D, 2013, TLM3D, 2012, a a , , c c Canton of Zurich Canton of Zurich , 2011, , 2012, 1 : 200000 , 2010, Canton of Zurich b d e ; Canton of Zurich ; Canton of Zurich erent receptors. ff Infrastructures, Natural and Semi- Natural Systems, Cultural Heritage ) 2 ) People, Buildings, Agriculture 1 − Kanton Zürich 1 : 5000 http://www.gis.zh.ch www.statistik.zh.ch www.gis.zh.ch www.gis.zh.ch http://www.swisstopo.admin.ch Geographic Information System WSL, 2006, 1 : 100000http://www.gis.zh.ch http://www.swisstopo.admin.ch Geographic Information System WSL, 1994, Canton of Zurichwww.blw.admin.ch www.bfs.admin.ch 7905 7906 Debris Factor People Water depth (m)Flow velocity (m s Flood extension (km People, Buildings ce. ffi ce for Agriculture. ce of Topography. ffi ffi ce of Canton of Zurich. ffi Flood metrics selected to assess hazard for di Summary of the dataset used for the application of the KULTURisk RRA methodology GIS Centre of Canton ofStatistical Zurich. O Swiss Federal O Swiss Federal Statistical O Swiss Federal O HAZARD ASSEMENT Selected flood metric Receptor Flood hazard a b c d e Roads (Strasse_CH_line) and WB_HW_IK300, IK100, IK30_F)People in residential areas Railways (Eisenbahn_CH_line) maps KantonSwitzerland Zürich CORINE 1 Land : 5000 Cover map map (Denkmalschutzobjekte)25 m Digital Elevation Kanton Model Zürich (DEM) 1 : 5000 Percentage of disable in Zurich city Kanton Zürich 1 : 5000, (Bevölkerung Gemeinden Quartiere) mapBuilding footprint map Canton of Zurich Protected objects of historical interest Digital map of soil coverage of Switzerland Flood hazard map (Gefahrenkartierung Hochwasser, Dataset Source Table 2. Table 1. within the Sihl River valley. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent pattern of water depths ff 1 0.25 2.00 < > for urban areas 1 − 7908 7907 2 m s ) Debris factor (DF) d 0.75 m 1 v > Depth classes1 [m] 234567 0.25–0.50 0.50–0.75 0.75–1.00 1.00–1.50 1.50–2.00 < d < 0.25 m0.75 or 0 ≤ ≥ Flood depth ( d 0.25m d Classification of water depths as provided by the GIS Centre of Canton of Zurich Guidance for the definition of debris factor (DF) for di Table 4. through flood hazard maps. Table 3. and velocities in urban areas (DEFRA, 2006). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , d ) as v 1 − s 2 ] 1 − 2.0 m 1 − 1 s − 2 d < s 2) [m s · , and velocity – 2 = d v < v 0.5 m · 2 m I/d 1 d − = s d < d > v 2 · · v v ]( 1 − Velocity ) from available data (water depths – 2 m or v 0.5 m or d > 0.5) [m s 2.0 m or 0.5m d < = v 7910 7909 · d < d < ). I ) [m] ( d Computation of (single) values of velocity ( Classification of intensity parameter (function of water depth – 12345 0.25 0.5 0.75 1 0 1.5 1 1 2.00 1 1 1.00 0.67 0.50 0.33 8.00 4.00 2.67 2.00 1.33 Depth Depth of DF Intensity class 1 Intensity classes 2 and 3 classes reference ( 6 and 7 2 1 0.25 1.00 3 High 2 Medium 0.5 Intensity classes Description Condition 1 Low Table 6. debris factor – DF, and intensity – Table 5. provided by the GIS Centre of Canton of Zurich through flood hazard maps. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , velocity – d 2) = v · ) classes 2 DF d I + 1.5 · d + v · d = 200 0.5) and 3 ( > ) class 1 Intensity ( I people = H v · d 7912 7911 ) Number of injuries 1 R ). I ) [m] ( d Risk classes ( Very lowLowMediumHighVery high 1–50 100–150 50–100 150–200 12345 0.25 0.5 0.75 1 0 1.5 1 1 0.875 1 1 2.25 2.625 3.75 3 2.375 4.125 3.75 5.25 4.5 Hazard scores to people computed from available data (water depths – Relative risk classes and range of values for injured people. Depth Depth of DF Intensity ( classes reference ( 6 and 7 2 1 4.5 6 , debris factor – DF, and intensity – Table 8. Table 7. v Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ] coverage 2 coverage % of % [#] [km 5 > 7914 7913 ) Number of fatalities 2 R Risk classes ( Very lowLowMediumHighVery high 1 3 2 4 Statistics about the buildings coverage along the Sihl River valley. Relative risk classes and range of values for fatalities. 111–112: Continuous urban fabric –121: Discontinuous Industrial urban or fabric commercial units122: Road and 18 rail 255 networks141–142: and Green associated urban land areas – 94.0 Sport leisureTotal facilities 8.9 83.4 295 100 1.5 0.5 780 0.1 0.3 4.0 0.6 3.1 1.4 12.9 19 430 100.0 10.7 100.0 Buildings: CLC class Total Table 10. Table 9. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ] [%] 2 erent CLC classes. [#] [%] [km ff 7916 7915 ) Description # of inundated buildings 3 R Risk classes ( Not at riskLowMediumHigh Not inundated Partial damage Inundation Total destruction 16 163 0 3267 0 Statistics related to the Risk for buildings for di Relative risk classes and range of values for buildings. Risk for buildings (CLC classes)1.1.1–1.1.2: Continuous urban fabric –1.2.1: Discontinuous Industrial urban or fabric commercial units1.2.2: Road and rail networks1.4.1–1.4.2: and 3075 Green associated urban land areas – Sport leisureTotal facilities 94.1 1.8 21 17 Flooded Flooded 0.6 83.4 Flooded area 0.5 154 Flooded area 0.004 4.7 0.1 0.2 0.3 4.1 12.4 3267 100.0 2.2 100.0 Table 12. Table 11. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ] 2 within each district [km] 7918 7917 ) Length of infrastructures at risk 4 R ) Description Agricultural areas [km 5 R Risk classes ( Very lowLowMediumHighVery high 0.01–7 14–21 7–14 28–32 21–28 Not at riskLowHigh Not inundated 7.08 Inundated Destructed 0 0.59 Risk classes ( Relative risk classes and range of values for agriculture. Relative risk classes and range of values for infrastructures. Table 14. Table 13. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ] 2 ] area [km 2 erent CLC classes. ff Total area Flooded agricultural 7920 7919 erent receptors by local relevant experts. ff Description ReceptorInfrastructuresBuildingsPeopleAgricultureCultural HeritageNatural and semi-natural systems 0 Weights 0.8 0.6 0.1 0.2 0.4 Weight assigned to di Statistics related to the Risk for agriculture for di CLC class 2.1.1CLC class 2.3.1Total Non-irrigated arable land Pastures 7.35 0.53 0.31 0.07 7.67 0.59 Agricultural typology (CLC classes) [km Table 16. Table 15. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

7922 7921

Total cisk classesVery low Score LowMediumHighVery high 0–0.048 0.096–0.14 0.048–0.96 0.19–0.24 0.14–0.19 . The case study area: its b) main characteristics. in Switzerland its location and a) . The study area: case 1 Total risk index classiﬁcation and range of values. The case study area: (a) its location in Switzerland and (b) its main characteristics.

Figure Figure

, 43

Sihl River ﬂowing ), source: O 1 − s (B) 3

7924 7923 Sihl study case related to a flood of 300event return period years

for on the Zurich main station, in box B the zoom on the upstream river valley . scenario Baseline 3 Baseline scenario for Sihl case study related to a ﬂood event of 300 years return Sihl River ﬂowing beneath Zurich main train station before it joins the Limmat River:

Figure Figure in box A the zoom area. image adapted from Google map; the box at the bottom shows the critical Sihl River

5 6 1 2 3 4 Figure 3. period, in box A thevalley zoom area. on the Zurich main station, in box B the zoom on the upstream river Figure 2. (A) section in August 2005 during a ﬂood even, source: A. Senn (WSL). underneath Zurich main train station in August 2005 (discharge: 280 m Waste, Water, Energy and Air, Zürich (M. Oplatka). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

45 44

7926 7925

isk map for fatalities level. District with statisticsisk map for at isk map for injured people injured withisk map for level. District statistics at Realtive r Relative Relative r . . 4 5 Relative risk map for fatalities with statistics at district level. Relative risk map for injured people with statistics at district level.

Figure Figure

46 47

7928 7927 isk (right) map for infrastructures (roads, railways, relative r

isk map of buildings (left) and a zoom on the city centre (right). (left) and zoom city a on the isk map of buildings

Relative Relative r . Exposure (left) and . 7 6 Exposure (left) and relative risk (right) map for infrastructures (roads, railways, Relative risk map of buildings (left) and a zoom on the city centre (right).

Figure Figure pathways).

Figure Figure

48 49

and destructed agricultural areas. A

at at risk (Langstrasse and City areas with their

7930 7929 hotspot ( Google maps modified. maps Google

Source: ). isk map for agriculture showing flooded ected area is reported. ﬀ bridges Relative Relative r Some relevant infrastructures

. . 9 8 Some relevant infrastructures (hotspots) at risk (Langstrasse and City areas with Relative risk map for agriculture showing ﬂooded and destructed agricultural areas.

Figure Figure is reported. area zoom most on the affected

Figure Figure roads, Zurich main Walchebrücke train station Hauptbahnhof (HB), Platzspitz, Bahnhofbrücke and

4 5 6 1 2 3 4 5 6 1 2 3 Figure 9. A zoom on the most a Figure 8. their roads, ZurichWalchebrücke bridges). main Source: Google train maps modiﬁed. station Hauptbahnhof (HB), Platzspitz, Bahnhofbrücke and Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

50 51

natural natural systems (left) with two zooms showing - 7932 7931 cultural heritage with two heritage zooms (right). cultural (left)

isk map for isk map for isk map for natural and semi Relative Relative r Relative Relative r . . 1 0 1 1 ected area (right). Relative risk map for cultural heritage (left) with two zooms (right). Relative risk map for natural and semi-natural systems (left) with two zooms showing ﬀ

Figure Figure

Figure Figure (right). area the most affected

3 4 1 2 5 4 1 2 3 Figure 11. Figure 10. the most a Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

7933 . Total risk map for the Sihl river valley considering the 300 years return period scenario. period return years 300 the considering valley river Sihl the for map risk Total . 2 1 Total risk map for the Sihl River valley considering the 300 years return period

Figure Figure

3 4 1 2 scenario. Figure 12.