224 Geographica Helvetica Jg. 54 1999/Heft 4

Impacts of Climate Change on Natural Hazards and Land Use in the Saas and Zermatt Valleys ()

Markus Stoffel, Fribourg The analysis and evaluation of existing policies de¬ fining danger zones and protecting civilians. In par¬ ticular the validity and appropriateness ofthe policies 1 Introduction are examined. At the same time, it is possible to build up a nearly complete record of natural hazard areas in Alpine Valleys - such as the Saas and Zermatt Valleys in the study region. the (Switzerland) - have always been influ¬ Assessment of the consequences of predicted climate enced by climatic fluctuations and natural catastrophes. change on natural hazards. This incorporates the def¬ The landscape is clearly marked by glacial, hydrologi- inition of potential high risk areas and an analysis of cal (i.e. torrential flooding) and gravitational processes the extent of these zones. (i. e. landslides, rockslides). Natural hazards have also strongly influenced the settlement of these steep and The final report of this diploma thesis (Stoffel 1999 a) narrow Valleys: as «safe» space was (and still is) rather was sponsored and published by the Swiss National Re¬ rare, areas suitable for village development were limit¬ search Program 31 «Climate change and natural haz¬ ed, keeping the number of inhabitants at a moderate lev¬ ards» (Bloetzer et al. 1998). el. In the middle of the 19th Century, English tourists dis- covered the Zermatt and Saas Fee regions. Today, tour¬ 2 Geography of the Saas and Zermatt Valleys ism is the main source of income for the area and the formerly predominant agriculture has lost its impor¬ The Saas and Zermatt Valleys are both deep mountain tance. As a result, the numbers of permanent residents Valleys in the Valais Alps (Switzerland). Surrounded by and holiday homes have rapidly increased. However, some of the highest peaks in the alpine are, the test re¬ space safe for construction has remained constant, and gion (520 km2) is strongly glaciated. The main source of the growth of these villages has already (or will soon income for the population of 16 810 is tourism: Nearly have) reached its limits. Considering the possibility of 1.5 million tourists are aecommodated annually in the climate change, land use planners will have to take tourist centres of Zermatt () and Saas Fee. these physical restrictions into account when defining developmental zones in the future. Climate change can Natural hazards are a part of life in the test region, limit- affect land use planning in two different ways: ing «safe» space on the Valley floors. Nearly all villages in the Saas and Zermatt Valleys are threatened by snow First, the spatial requirements of current land use avalanches, rockfalls, land- or rockslides, floods and could be modified by climate change, new needs debris flows. Most of these events are initiated at high could arise. altitudes (Highest peak: Peak 4545m above sea Second, climate change could affect the nature and level), crashing several hundreds of metres down into magnitude of natural hazards. Depending on whether the steep and narrow Valleys (Lowest site: 710m the risk of danger increases or decreases, space will above sea level). Land use planning is, therefore, rather either be lost or won. limited by the availability of suitable space.

Thus, the prospect of climate change leads to new inse- curities. The resulting conflicts will be especially seri- 3 Land use planning and natural hazards in ous when existing uses are impinged upon by new or Switzerland modified potentials of natural dangers. Predictions of possible changes are, however, difficult to make and are 3.1 Legal basis always linked with major uncertainties. For this reason, The goal of land use planning is to guarantee an expedi- it is important to note that the assessments presented in ent and economical use ofthe soil and an orderly devel¬ this paper may be possible, in some cases even proba¬ opment of the country. The Swiss Government has ble, but they are not «real time» predictions. Land use drafted constitutional articles, several federal laws, Stat¬ planning on the other hand has a direct influence on fu¬ utes and decrees to enforce these targets - forming the ture decisions and is consequently of economic impor¬ Land Use Planning Act of 1979. Itdefmes the principles tance. This paper, therefore, focuses on the following for an appropriate development ofthe country but gives two aspects: the Cantons the liberty to define legal articles at the can- Impacts of Climate Change on Natural Hazards and Land Use Markus Stoffel 225

GERMANY feet above sea level

12 500 Basel glacier debacles Zürich AUSTRIA debris flows 10 000 Berne landslides Davos rockslides 7500 ^ rockfall Sion Locarno 5000 floods Geneva

2500

& earthquakes Saas Zermatt Valleys villages test reqion

Fig. 1: Geographical location ofthe Saas and Fig. 2: Mostly all catastrophic events in the Saas and Zermatt Valleys (Valais, Switzerland) Zermatt Valleys Start at high elevation sites to reach the Lage des Saas- und Nikolaitals (Wallis, Schweiz) narrow Valley floor: note the position ofthe villages Localisalion des vallees de Saas et de Zermatt often situated on mountain torrent alluvial fans (Valais, Suisse) Eine grosse Zahl katastrophaler Ereignisse des Saas- und des Nikolaitals finden ihren Ursprung in hohen Lagen, um alsdann den engen Talboden zu erreichen; die Dörfer der untersuchten Region befinden sich tonal level. The land use planning Statute thus has a häufig auf Wildbach-Schuttkegeln strong local basis. In spite of the cantonal and commu- La plupart des evenements catcistrophiqiies de la region nal differences, a Standard procedure at three different de Saas et de Zermatt se declenchent ei haute altitude levels is always followed (Bloetzer et al. 1998): pour atteindre finalement le thalweg enserre des vallees; noter la frequente localisalion des villages sur At the level of the cantonal general plan, large areas, les cönes alluviaux de torrents (de montagne) laterau.x supraregional functions and criteria for the zoning plan are defined. At the level of the communal zoning plan, uses and limitations with obligations for the landowners are ried out. the results of which are presented in hazard determined. maps distinguishing between three degrees of danger Finally, the issuance of building permits enables the (see Figure 3). authorities to control and supervise imposed obliga¬ Every municipality has to map hazardous regions be¬ tions and restrictions. fore defining future residential or industrial zones. This way, hazard mapping helps guarantee long-term plan¬ In addition, one has to consider that land use planning ning measures: new buildings may only be constructed measures have long-term effects and that once residen- in areas where they are exposed to no or little danger. tial or industrial zones have been developed, the land After major events, the hazard maps have to be revised use is practically irreversible. For this reason. the consti- and adapted to the new Situation. The Grossgufer rock- tutional principles of law and order need to be respected. slide (1991) - involving 30 million m' of rock - buried whenever there are interventions in private property. 33 buildings near the village of Randa (Zermatt Valley). Reclassification of residential zones was necessary after 3.2 Hazard mapping this event (Stoffel 1999 a). At the cantonal, communal and individual planning levels, natural dangers are taken into account in several ways. The Federal Land Use Planning Act of 1979 - as 4 Changing natural hazards by climate changes well as the Federal Forest Act, the Federal Hydraulic Engineering Act (both of 1991) and their corresponding 4.1 Test region climate of the 21st Century decrees and explanations clearly define guidelines In its Climate Change 1995 report. the Intergovernmen¬ for drawing up catastrophe catasters of past events as tal Panel on Climate Change (IPCC) estimated that the well as lists of endangered areas. On the basis of the global mean surface air temperature would increase by catasters and lists, simulations and calculations are car- about 2° Celsius between 1990 and 2100. In the south- 226 Geographica Helvetica Jg. 54 1999/Heft 4

ern part of the , the increase could be as high Although less common than floods or debris flows, the as 0.5 to 1.5° Kelvin in winter and 2 to 4° Kelvin in destruetive capacity of fast-moving slides of large ice summer by 2050. Preeipitation is likely to decrease dur¬ masses known as glacier debacles on buildings and in- ing the summer (-10%) and increase during the winter frastrueture is high. The Allalin glacier debacle (Saas season (+10%) (IPCC 1996; Ohmura, Beniston et al. Almagell) of 1965 buried 88 Mattmark dam construc- 1996). tors and completely destroyed all ofthe cabins. To avoid Considering the probability ofthe climate change fore- a similar disaster, many glaciers in the Swiss Alps are cast, those involved in planning questions will have to regularly controlled, making the risk of unexpected take this new aspect into consideration when allocating slides rather low. uses to available areas, particularly as a changing cli¬ An increase of the present temperatures will probably mate can influence the risk of natural hazards. Conflict lead to a partial thawing ofthe uppermost layers of per- potential is high where existing uses are affected nega- mafrost soils and rock glacier ice at higher elevations. tively by new or modified potentials of natural dangers. As a consequence, loose talus lose the cohesive effect of Therefore, climate change and the resulting modifica¬ the ice («ice-concrete»), and debris flow is made possi¬ tion of natural hazards lead to new insecurities. ble. Historical records indicate that the events in recent times have increased at an alarming rate. It may thus be 4.2 Modified natural hazards assumed that the number and volume of future debris Warmer temperatures and a greater occurrence of indi¬ flows reaching the alluvial fans and the villages of the vidual climatic extremes will probably influence some Saas and Zermatt Valleys will increase. As a result, less natural hazards in the Saas and Zermatt Valleys more land is available for development. To be able to make a than others. Rockslides, large landslides and snow clearer picture of future events, general studies on per- avalanches are not expected to be affected much by cli¬ mafrost modification in the zone of origin will be neces¬ matic variations, on the other hand the occurrence of sary. In addition, geomorphological research ofthe allu¬ flashfloods, glacier debacles and cryospheric debris vial fans could east more light on possible debris flow flows could easily be more frequent (Bader & Kunz paths. 1998), particularly in the late summer and in autumn (Zimmermann et al. 1997a, b, Rebetez et al. 1997). Floods in the Saas and Zermatt Valleys often occur after 5 Conclusions heavy summer thunderstorms or when extended preeip¬ itation touches on the dry, leeward areas affected by 1. The mandate to assess and eliminate danger zones as foehn. The occurrence of these climatic events appears far as possible, as well as to restrict development to to be increasing, causing major damage most recently in areas of low risk gives Swiss land use planning au¬ 1987 and 1993. Maps of detailed flood risk areas are in thorities an adequate System to provide optimal safe- preparation. ty conditions. Nevertheless, a certain element of inse-

What do the different colors in natural hazard risk maps mean in terms of «danger»?

red: people and animals are seriously endangered both inside and outside buildings => no constructions allowed in this area blue: people and animals are seriously endangered outside buildings => limited construction possible (reinforced concrete, small or no Windows,...) yellow: people and animals are lightly endangered outside buildings => no restrictions white: no danger

For buildings with a temporary or permanent concentration of people (e. g.: schools, churches), special regula- tions are applicable. Such construction is only possible in the yellow or the white zones.

Fig. 3: Regulations on endangered areas and building space for land use planning purposes in Switzerland Empfehlungen des Bundes zur Bezeichnung von Gefahrenzonen und damit verbundene Folgen für die Raumplanung Recommandations föderales pour Tetablissement des zones ä risque et consequences pour Tamenagemenl du territoire (BUWAL, BWW & BRP 1998, 1997; BFF & EISLF 1984) Impacts of Climate Change on Natural Hazards and Land Use Markus Stoffel 227

curity in predicting hazardous areas will always exist, thank all researchers of the National Research Program and hazard mapping will always be an ongoing proc¬ 31, especially Dr. Pierre Kunz, University of Geneva, ess. Dr. Markus Zimmermann, Bern and Profs. Michel 2. The predictions of possible modifications to natural Monbaron and Martin Beniston, University of Fri¬ hazard patterns due to climatic change is a real chal¬ bourg. lenge for land use planners, particularly as the predic¬ tions are not easy to make and carry a great degree of uncertainty. As a precaution, «buffer areas» or zones Literature Cited of potential high risk should be allowed for («Ge¬ Bader, S. & P. Kunz (1998): Climat et risques naturels fahrenerwartungszone»). The definition of zones of - La Suisse en mouvement. - Final Report National potential high risk has two advantages: first, con¬ Research Program 31, Zürich: 1-312 struction in such areas can be delayed while carried BFF & EISLF (1984): Richtlinien zur Berücksichti¬ out elsewhere; second, areas are clearly demarcated gung der Lawinengefahr bei raumwirksamen Tätig¬ for careful Observation and risk development study keiten. - Bern: EDMZ. (Stoffel 1999 b). Bloetzer, W., Egli, T, Petrascheck, A., Sauter, J. 3. Land use planning is not expected to change funda- & M. Stoffel (1998): Klimaänderung und Naturge¬ mentally due to modified climate conditions, particu¬ fahren in der Raumplanung - Methodische Ansätze und larly as the prediction of potential natural dangers is Fallbeispiele. - Final report National Research Pro- at present difficult enough, perhaps even more diffi¬ gram 31, Zürich, vdf: 1-200. cult than calculating the effects of climate change on BUWAL, BWW & BRP (1998): Naturgefahren; these natural processes. Nevertheless, in order to en- Berücksichtigung der Massenbewegungsgefahren bei sure present and future safety of the population it is raumwirksamen Tätigkeiten. - Bern. EDMZ. absolutely necessary to take potential problem areas BUWAL, BWW & BRP (1997): Naturgefahren; Emp¬ into account when assigning new land uses. fehlungen zur Berücksichtigung der Hochwasserge¬ 4. Far more important than the definition of legal princi¬ fahren bei raumwirksamen Tätigkeiten. - Bern, EDMZ. ples at the Community level is a clear and logical de¬ IPCC (1996): Climate Change 1995: The Science of scription of the impending danger. If the local popu¬ Climate Change. Contribution of Working Group I to lation is aware of the possible danger and is able to the Second Assessment Report of the Intergovernmen¬ understand why certain measures have to be taken, it tal Panel on Climate Change. - Cambridge: Cambridge will be easier to implement the appropriate measures University Press. required by existing law. This link to the population is Haeberli W., Kääb, A., Hoelzle, M., Boesch, H., all the more important if precautionary measures are Funk, M., Vonder Muehll, D. & F. Keller (1999): to be taken with regard to new dangers and those in¬ Eisschmelzen und Naturkatastrophen im Hochgebirge. fluenced by climatic Variation. - Final report National Research Program 31, Zürich, 5. Risk communication is, therefore, a central element vdf: 1-150. of natural hazard control. Particularly the inhabitants Ohmura, A., Beniston, M., Rotach, M., Tschuck, of mountain regions are used to living with natural P, Wild, M. &M.R. Marinucci (1996): Simulation of dangers. They are aware that absolute security and Climate Trends over the Alpine Region. - Final report predictions free of mistakes are not possible. As the National Research Program 31, Zürich, vdf: 1-197. local population on the one hand has to support and Rebetez, M., Lugon, R. & P.-A. Baeriswyl (1997): accept risk management and on the other hand has to Climatic Change and Debris Flows in High Mountain make a living in situ, it should be more strongly in¬ Regions: The Case Study of the Ritigraben Torrent volved in the decision making process. It should, (Swiss Alps). - In: Climate Change 36: 371-389. therefore, be a central task of science to describe pos¬ Stoffel, M. (1999 a): Klimawandel als Heraus¬ sible changes in a clear and intelligible way, thus en- forderung für die Raumplanung der Vispertäler. - Di- suring a good basis for communication between all ploma thesis, Department of Geography, University of parties involved. Fribourg, Fribourg: 1-89. Stoffel, M. (1999 b): Geomorphologie et amenage- Acknowledgements ment du territoire. - In: Research Report 1998, Institut This paper partly draws on the work of the reserach de Geographie, Universite' de Fribourg, Fribourg: 36- group «Climate Change and Natural Hazards in Land 37. Use Planning» under the National Research Program Zimmermann, M., Mani, P, Gamma, P, Gsteiger, P, 31 «Climate Change and Natural Hazards». The contri- Heiniger, O. & G. Hunziker (1997 a): Murgangge¬ bution of the following project members is acknowl- fahr und Klimaänderung-ein GIS-basierter Ansatz.- edged: Werner Bloetzer, ; Dr. Thomas Egli, St. Final report, National Research Program 31, Zürich, Gallen; Dr. Armin Petrascheck, Biel and Joseph vdf: 1-162. Sauter, Chur. In addition, the author would like to 228 Geographica Helvetica Jg. 54 1999/Heft 4

Zimmermann, M.. Mani. P. & H. Romang (1997 b): werden, um Konflikte in Zukunft so gut wie möglich zu Magnitude-frequency aspects of alpine debris flows. - verhindern. Schliesslich spielt auch der Kontakt zwi¬ In: Eclogae Geol. Helv. 90: 415-420. schen Experten und der Bevölkerung eine vvichtige Rol¬ le. Die Risikokommunikation ein zentrales Element im Umgang mit Naturgefahren darstellt. Summary: Impacts of Climate Change on Natural Hazards and Land Use in the Resume : Impacts du changement climatique sur Saas and Zermatt Valleys (Switzerland) les risques naturels et l'amenagement du territoire The aim of Swiss land use planning is to guarantee an dans les vallees de Saas et de Zermatt (Suisse) expedient and economieal use ofthe land and an orderly L'amenagement du territoire a comme lache de garamir development of the country. Therefore. land use plan¬ une affeciation appropriee et econome du sol et une oc- ning has to designate areas suitable for optimal econom¬ cupation rationnelle du territoire. Dans ce but. il doit ic development. The possiblility of climate change pos- creer les conditions-cadre ä un de'veloppement econo¬ es a special challenge for land use planners. This paper mique optimal, dejä lors des periodes de planification. examines the implications of environmental change re¬ Les changements climatiques representent une prebc- sulting from climate change and anticipates new zones cupation actuelle d'importance croissanie, devant etre of conflict between existing and future land uses in the prise en compte par les amenagistes en complement aux Saas and Zermatt Valleys (Valais. Switzerland). Differ¬ aspects economiques de l'amenagement du territoire. ences between the «reul-time- decisions of planners Le but de ce travail fut de demontrer et d'analvser les and the possible development of nsks and changes pre- dangers existants ainsi que les «dangers futurs» d'un cli¬ dicted by scientists are key factors examined in this pa¬ mat plus chaud dans les Vallees de la Viege (Vallee de per. Furthermore, this paper investigates the legal impli¬ Saas et de Zermalt. VS. Suisse). En outre. les resuliats cations of land use planning under conditions of doivent etre mis en relation avec les documents qui re- climatic uncertainty. Particular emphasis is given lo the gissenl l'amenagemeni du territoire (p. ev: plans various ways natural dangers can be taken into account d'affectalion), sans oublier que ces modifications peu¬ at the levels of the «cantonal» general plan, communal vent etre possibles, parfois meme probables, mais zoning plan and the issueing of building permits. Final¬ qu'elles ne representent pas des prognostics en «temps ly, this paper recommends the establishmenl of «buller reel». Par contre. les decisions au niveau de areas» or /ones of potential high risk as precautionary l'amenugment du territoire consistent toujours en des measures and Highlights the fundamental necessit) of solutions en «temps reel» et ont comme telles des con¬ risk communication for natural hazard control. sequences economiques majeures. Dans ce sens. ce pa- pier propose pour l'instant une dctcrmination de zones ä Zusammenfassung: Auswirkungen des danger du style «zone-tampon» ou /one de danger at- Klima wandels auf die Naturgefahren und die tendu. Cette politique preVoyante et restrictive doit etre Raumplanung des Saas- und Nikolaitals (Schweiz) appliquee au niveau du plan directeur cantonal. au ni¬ Es ist die Aufgabe der schweizerischen Raumplanung, veau du plan d'affectalion communal ei lors de eine zweckmässige und haushälterische Nutzung des l'autorisation de construction communale. Dans cette Bodens und eine geordnete Besiedlung des Landes si¬ perspective, le dialogue ä propos du risque entre specia- cherzustellen. Daher muss die Raumplanung für die listes et populalion doit former un element central dans Planungsperioden die raumlichen Voraussetzungen für le comportement face aux dangers naturels. eine optimale Wirtschaftsentwicklung schallen Als zu¬ sätzlicher Faktor ist nun nebst der Wirtschaftsentwick¬ lung auch die sich anbahnende Veränderung des Klimas zu berücksichtigen. Die vorliegende Arbeit versucht, das aktuelle Gefahrenbild in der Testregion «Vispertä- ler» (Saus- und Nikolaital. Wallis. Schweiz) zu erläu¬ tern und auf mögliche Verandeningen des Gefahrenpo- Icntials hin zu untersuchen. Dabei muss aber immer beachtet werden, dass die aufgezeigten Entwicklungen Dipl -Geogr. Markus Stoffel, Institut de Geographie de zwar möglich, mitunter gar wahrscheinlich sind, jedoch IT'nivcrsite de Fribourg / Geographisches Institut der keine Vorhersagen in «Echtzeit» darstellen. Im Gegen¬ Universität Freiburg. Pcfolles. CH-1700 Fribourg. salz dazu stellen raumplanerische Beschlüsse Entschei¬ e-mail: markus.stoffcKs unifr.ch de in «Echtzeit- dar und haben somit schwerwiegende wirtschaftliche Konsequenzen IX-shalb sollen bei mög¬ Manuskripteingang/rectived/rrntrfe du manuscrit: lichen künftigen Gefahrenveränderungen bereits heute .W.0S.I999 vorsorgliche Erweiterungen von Gefahrengebieten als Annahmt- zum Dritt"k/Accepted for publication/ «Gefahrencrwartungs-» oder Pufferzonen bezeichnet acetptalion u l'imprrssion: l5.l.2tXX)