Giant Mts. are the highest and the only mountain range of the Czech Republic which features considerable avalanche activity. There are at average 22 avalanches events on 47 avalanche paths in a year. Human colonisation and subsequent exploitation during the 16th and 17th centuries led to the growth of treeless area which resulted in an increase of avalanche paths. Reforestation in the course of the 18th to 20th centuries has decreased the risk of spread of avalanches. Since 1980 the Giant Mts. have been strongly afflicted with emissions. Norway spruce monocultures have started to die off, the avalanche cadastre has risen again. Partial analyses reveals that the intensive avalanche activity has been (even in the past) bounded to extraordinary climate conditions and thus the growth of the avalanche cadastre can not be related exclusively to the decline of protective function of the forest. Natural development of mountain slopes should not be omitted as this process includes both snow avalanches and debris

Kocianova, Milena

Spusta, Valerian ,

English

Norwegian Geotechnical Institute (NGI) Digital Archive

274Changes of the avalanche cadastre in theCzech part of the Giant Mts.Valerian Spusta, Milena KocianovaAdministration of the Krkonose National Park, 54302 Vrchlabi, Czech RepublicABSTRACT. Giant Mts. are the highest and the only mountain range of the CzechRepublic which features considerable avalanche activity. There are at average 22avalanches events on 47 avalanche paths in a year. Human colonisation and subsequentexploitation during the 16th and 17th centuries led to the growth of treeless area whichresulted in an increase of avalanche paths. Reforestation in the course of the 18th to 20thcenturies has decreased the risk of spread of avalanches. Since 1980 the Giant Mts. havebeen strongly afflicted with emissions. Norway spruce monocultures have started to die off,the avalanche cadastre has risen again. Partial analyses reveals that the intensive avalancheactivity has been (even in the past) bounded to extraordinary climate conditions and thus thegrowth of the avalanche cadastre can not be related exclusively to the decline of protectivefunction of the forest. Natural development of mountain slopes should not be omitted asthis process includes both snow avalanches and debris.NATURE CONDITIONSThe Giant Mts. (called Krkonose 1Karkonosze in the Czechand Polish, respectively) form a part of the CentralEuropean branch of the Hercynian mountain range - in factits highest part called the High Sudetes. They constitute theborder mountain range between the Czech Republic andPoland, they reach the altitude of 1602 m and unlike theneighbouring middle-mountains of the Central Europe theymarkedly surpass the alpine timberline over some IS km.Because of their extraordinary nature values the Giant Mts.have been protected as national parks on the Polish and theCzech sides since 1959 and 1963, respectively. In 1992 thewhole area was declared a bilateral biosphere reserve.Development of the Giant Mts. relief was vastlyinfluenced by weathering and denudation of crystallinemetamorphic rock and granite in the warm and humidclimate of Mesozoic Era, renewed fluvial erosion in thecourse of the Tertiary and by Pleistocene glaciation. Thewest-east orientation of main windward valleys, two summitplateaux at the high of 1340 and 1400 m a.s.l. and a fan of aleeward slopes of glacial cirques (anemo-orographicsystems sensu Jenik, 1961) present characteristic traits ofthe Giant Mts, Geographic position of the Giant Mts. at thesouthern margin of German - Polish lowlands and the west-east orientation of main valleys predispose attacks of strongand cool northern winds as well as prevailing western oceancurrent on the summit areas. The climate of the alpine areais consequently quite severe; average year temperature is Oto loe, precipitation rate is 1500 mm, snow cover lastsfrom November to May and reaches average thickness of190 cm, avalanche activity is unusually frequent for themiddle-mountains (47 avalanche paths are known on theCzech and another 36 ones on the Polish sides). From theforestry typology point of view forest stands of the 6altitudinal vegetative stages are developed (dwarf pine zoneincluding area of arctic-alpine tundra Isensu Soukupova etal., 1995/, spruce, beech-spruce, spruce-beech and fir-beechzones).SETTLEMENT AND AVALANCHESThe Giant Mts. are really densely populated, there arenumerous mountain villages, tourist centres, mountainchalets and rich network of tourist paths which often crosseven avalanche fields. Each year as many as 5 milliontourists arrive to visit the Giant Mts. The systematicsettlement of the Giant Mts. began in the 16th century as aresult of the rise of mining and chalet farming. Naturaldisasters such as snow avalanches, debris or floodsgradually made the inhabitants abandon the endangeredareas. Nowadays all the chalets are accessible from variousdirections which enables to avoid avalanche fields. Anumber of winter accidents that happened (67 persons diedin avalanche events during 300 years) led to theestablishment of the Mountain Rescue Service in 1934. Itsinvolvement in snow observation and avalanche control hasbeen initiated in 1954,. since 1962 the Service has dealtwith regular weekly monitoring of avalanche conditions,recording of all avalanche events and their descriptionbased upon international classification (Spusta, Jenik,Kocianova, Sprava KRNAP Vrchlabi, 1997). If there is adanger of an avalanche event, the corresponding avalanchefields are immediately closed to public attendance. In thelast IO years the avalanche caused the death of 1 persononly.AVALANCHE CADASTRE AND ITS CHANGESIn 1962- 1997 there were 698 avalanche events on the Czechside. About 75% of avalanche paths coincide with locationsof Pleistocene glaciers and nivation niches. Avalanches areof small or medium sizes with maximum length of 1500 mand width of 250 m which is due to the relief of themountain range. Zones of avalanche origin take place onsmall area (only 15x4 km) and are mostly situated above thetimberline or along the upper timberline (1250 - 1602 ma.s.l, /Jenik, J. et Lokvenc, T., 1962/). Avalanche pathsclimb up in to the montane zone to the maximum of 870 mwhich means they reach the Norway spruce -beechvegetative zone too.The avalanche activity is assumed in the GiantMts. since the end of Tertiary in connection with gradualcooling of the climate. According to written records (thefirst mention comes of 1456) there were major avalancheevents in the 16th and 17th centuries - colonisation andsubsequent exploitation (mining, timber-cutting, farming)led to the growth of treeless area which resulted into theinerease of avalanche paths. Reforestation of mountainslopes in the course of 18 th -20 th centuries has decreasedthe risk of spread of avalanches. However, mostly non-native seedlings (imported from the Alps) used for thereforestation were less resistant to stress than the nativepopulation. Since the 1980 the Giant Mts. region has been apart of the so-called "black triangle" in Central Europe thatis the area strongly afflicted with emissions. The action ofwide spectrum of emission substances leads to dying off offorest in a great scale, to its cutting and subsequentdisaster caused by the insects.When the evaluation of the avalanche cadastrewas carried out in 1989 (Vrba et Spusta, 1991) it was find-out that roughly 1/3 of all the avalanche paths enlarged andextended. These changes were put into the relation withdying-off of forest as a result of emissions and with thedecline of its function as a protection barrier. The firstapparent changes of Norway spruce complexes wererevealed in 1977 (Vacek, Podrazsky, 1995). Physiologicalchanges of needles already appear when the S02concentrations in air reach the level of 15¡'¡'g/m3 (Materna,1979). Within 1984 -90 the measurements conducted on thesummit area of the Giant Mts. (Schwarz, Sprava KRNAPVrchlabi,m.s., 1990) showed the average year values from10,3 to 26,7¡.¡.g S02/m' of air with the highest value of160,34¡.¡.g S02/m3 of air. The decrease of emissionproduction of power stations in the former GermanDemocratic Republic and in the Czech Republic since 1991is the reason why the contemporary state of the air in the275Giant Mts. can be denoted as emission free (Vacek,Podrazsky, 1995).More detailed assessment of avalanche cadastrefrom the monitored period of 1962/63 - 1996/97 shows thefollowing facts: The avalanche cadastre has risen againabout 1/5 up to contemporary 450 ha which equals about10% of the core area of the Krkonose National Park. In totalthe changes of 18 avalanche paths were recorded (fig. I.),26 ha of forest were destroyed. In nine cases the firstchanges (in the sense of the spread and extension)happened before 1977/78, i.e. before the main emissionaction. After 1977/78 four new paths turned out (two ofthem had connection with debris) and next four paths wereindicated as a short snow motion with the connection ofdebris as well. Most of changes took place in years whichhigher avalanche activity occurred (more than 30 avalancheevents in a winter season) - there are 1969/70, 1975/76,1986/87, 1987/88 or in connection with a sudden change ofclimate conditions (great amount of now snow, temperaturecollapses, windstorm) which resulted in general shortgrowth of avalanche activity (11 - 34 events in a month) -1962/63, 1964/65, 1967/68, 1970/71, 1981/82, 1985/86,1994/95 (Spusta, Sprava KRNAP Vrchlabi,m.s., 1996).The changes are not concentrated in glacialcirques where avalanche paths are predisposed with regardto rocky slopes but in two young erosion valleys withforested slopes (avalanche paths no. 9-19). Important traitof this area is a high number of debris. In the line 2 kmlong there are 12 and 65 debris, respectively whichcoincide with avalanche paths quite often. The presence ofdebris confirms the existence of natural dynamicdevelopment of slopes with great relief energy (Pilaus,1977). Even though it is evident, that the process of dying-off forest increases the possibility of avalanche events, butthis phenomenon is not the only cause of avalanchecadastre changes. Historical records mention big avalancheswith devastating effects in 1819,1827,1844,1887,1956 inconnection with high snow precipitation. The year of 1956is especially important because of the forests were notdevastated neither by the extreme exploitation noremissions nor the insects. The avalanche events ran on 8March 1956 destroyed 12 ha of forest (Vrba, 1969). Thatday the biggest event occurred on a newly developedavalanche path on a slope covered by 150 years old forest.BENEFITS OF THE AVALANCHESIn the course of the Postglacial period, including' theclimatic optimum suitable for expansion of forest, the snowavalanches continually prevented the invasion of forest treesand thus secured the survival of rare arctic and alpineorganism. Also, various rare lowland non-Jorest specieshave found their refuge on the avalanche tracks. Theavalanche-prone slopes and cirques served also as cradlesof new species, and thus became remarkable centres ofbiotic micro-evolution. Several new species of plants havebeen first identified for science in populations restricted tosmall areas of the active avalanche fields. As the presenttime, a consensus exists that avalanche activity in theuppermost altitudes of the Giant Mts. should not be human-controlled and that the active avalanche fields represent themost valuable sanctuaries in the national parks (Jenik 1961,Spusta, Jenik, Kocianova, Sprava KRNAP Vrchlabi,m.s.,1997).CONCLUSIONA valanches constitute a natural and integral part of theGiant Mts. nature. The changes of the avalanche cadastreREFERENCESJenik, J. 1961. Alpinska vegetaee Krkonos, KralickehoSnezniku a Hrubeho Jesenik: teorie anerno-orografickych systernu. Praha.Jenik,J.et Lokvenc,T. 1962. Die Alpine Waldgrenze imKrkonose Gebirge. Rozpravy CSA V, r. mat. prir.Ved, 72, 1-65.Materna). 1979. Vliv imisi na lesni porosty CSR. InSbornik referatu Z odborneho seminareProblematika lesu v KRNAP, Sprava KRNAP,Vrchlabi,21-37Pilous,V. 1977. Strukturni mury v Krkonosich III. OperaCorcontica, 14, 7-94.Schwarz, O.1990.Vysledky rnereni prurnernych dennichkoncentraci sloucenin siry v Krkonosich. m.s,dep. In Sprava KRNAP, Vrchlabi.276primarily result from the influence of natural factors(climate conditions or relief development) and partly alsofrom the influence of human activities (deforestation).In the last 20 years forests of the Giant Mts. havedyed-off on a great scale. The process was caused byemissions and decreased the ability of forest to act asavalanche barrier. Although the air situation has beencharacterised as emissions free since 1991, long-lastingdevelopment of consequences of this ecological disaster hasbeen expected, there might occur even some biggersubsequent changes of avalanche cadastre ..Soukupova,L., Kocianova,M., Jenik,J., Sekyra.L, eds.1995. Arctic-alpine tundra in the Krkonose, theSudetes. Opera Corcontica, 32,5-88.Spusta,V. 1996. Lavinovy katastr Krkonos. m.s. dep. InSprava KRNAP, Vrchlabi.Spusta,Y. Jenik.J, .Kocianova.M, 1997. Avalanche activityin the Giant Mts., the Sudetes., m.s. dep. InSprava KRNAP, Vrchlabi.Vacek.S. et Podrazsky.V., 1995. Development trends inforests of the Krkonose Mts. under emissionload. In Flousek, J. et Roberts, G., eds. Mountainnational parks and biosphere reserves:Monitoring and management. Proceedings ofthe International Conference, Spindleruv Mlyn.20 - 23 September 1993, Vrchlabi, SpravaKRNAP,69-75Vrba,M. 1969. Laviny v Krkonosich. In Fanta et al. PrirodaKrkonosskeho narodniho parku. Praha. 102-111.Vrba.M. et Spusta.V. 1991. Lavinovy katastr Krkonos,Opera Corcontica, 28.,~:<",~~~.;';·~,'>Qi'. ' - .~'. ...,,_. .• M •• ~ '.", / "-'",." .~' •• ,'_ •.OM,\. ",./"~/J' ' -,·./í~\ '-,J~j~;"-' .. . ". ....•~~.... ,; :.. "'._ \.,\~:""""-,,~<~,,,\,~*./'::{;> ~..• ..~:i.>.,'!ê;}:~:'?~,\~::~.:• , .. ..., ./ . "'" .. ,. .<:: I I '.' .,.. , ; .....~ '\''':: ~:.~::~~~:~~f~i~~~;;;¡;~~:>~...~~~~:\:\;.. :.\ j . ..\ _"... "'~~"-" '. _"" .. _,., • " " " ." -,. j I i, , ,~, '_". '. ..... '., "; '_o. " ._ , '. I -, .. . ., ..'. ' . ...... .....-C· ! ! .... " .. "_"""'_ '." ". , '.' . "v-I..'· " . ". '•. '~"'" ,' . ~ -, /<!'" "•.,....... ./ 'O. !, "', , , "."~". / / ·,,1 / '" \ '."t' / ....''',\ I" " . ' •,......, . :><:,; '-..::.' ./. " \,,' '. \ . . '. \ G' \ .",.-"-"".,,,:::_. _.',," \~: " ..... ':-, .'--','~"\\\.'.j~-, !f'..~~:::..~\::\V;:~~·~)·,:;·~;.'C\ :il' I \ 130D"'f~' ' ..> .., '.~, /J ...... ':// '~>:.:.~.//''''''.< / ......., ....._ ~/' :. ,\ !,.....1#'",.........~,,-- ..", "\ " \ ". /-' .... /./-,POLAND... ', (" -_._-.'," "~~~,\:. / ....... '.--'. _' ~','\.'~'''',,, '....._/ / j ,!.. ".!; ¡II /;\.~:~.;:/);)\~~~. ': .,.i . ''''"'\ '.\ \ \1 " ¡ :\ •• MO",'.... '" .... ,. ),/¡....__...... ".,. ,; /.' ,,' /'/',; i .,/',,,/'" ........ ",",/ ,.--,'_'..............,/./ ..:" .....,,',. .0".-(....!--;-... \.,.'/ ,//,-- .'---,/)I,~Fig 1. Avalanche paths (No. 1-37 and their changes) in the Czech territory (V. Spusta,1996),and in the Poland territory (A. Brzezinski, 1997 - changes were not monitored)•Explanations: • Original avalanche pathsD Changes (growing, enlarging, joining)DChanges (growing, enlarging, joining)• Mountain dormitoryduring 1965-1975during 1976-1996,e'' ..,. ¡,.-::L, ·"T.,l ...·'.D" \1 .....

Changes of the avalanche cadastre in the Czech part of the Giant Mts.

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Changes of the avalanche cadastre in the Czech part of the Giant Mts.

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