Hans Kienholz

ASSESSMENT OF GEOMORPHIC HAZARDS AND PRIORITIES FOR FOREST MANAGEMENT ON THE RIGI NORTH FACE, SWITZERLAND

The Rigi Mountain is situated about 15 km east of Lucerne, Switzerland. This general area, located on the northern border of the Swiss Alps, receives high annual precipitation totals. Therefore the Gotthard railroad, which carries very heavy traffic, is endangered by rockfalls and mountain torrents. In addition, the forest on the Rigi North Face above the railway line, although zoned as protection forest, is showing extensive damage believed due to air pollution. Thus, its effectiveness as protection against hazards must be examined. This paper describes very detailed field observations with a high degree of objectivity, that led to maps of the dangerous processes. These included the entire section of the railway track and all possible danger locations. A geographical information system, covering each forest plot and the potential damage, provides a basis for rapid information up-dating. From this, priorities and procedures for developing protective measures can be derived.

STABILITY, INSTABILITY, AND CONDITIONAL INSTABILITY MOUNTAIN ECOSYSTEM CONCEPTS BASED ON A FIELD SURVEY OF THE KAKANI AREA IN THE MIDDLE HILLS OF NEPAL

The Mountain Hazards Mapping Project, sponsored by the Nepal National Committee for MAB and the United Nations University, is concerned with (1) the production of prototype maps to show slope stability and mountain hazards in Nepal and (2) the development of corresponding methods for assessing mountain hazards. In concurrence with the theme of the UNU Berne-Riederalp Workshop, September 1981, information gathered in the Kathmandu-Kakani area can be summarized as follows: due to natural factors (monsoonal climate, heavily weathered metamorphic rocks, steep slopes) the entire terrain of the field area is conditionally unstable. Intensive cultivation increases the danger of irreversible damage (i.e., deep-reaching soil erosion) and of instability as defined during the workshop. On the other hand, local farmers furnish an enormous stabilizing input by maintaining the cultivated terraces (some of which are irrigated). Consequently, the danger of reversible instability, that which can be corrected within a generation, is considered to be generally high. The danger of irreversible instability, at least under present-day circumstances, is considered to be relatively low. It is impossible to define unconditionally the amount of data essential to such investigations. Rather, the minimum data need must be adjusted to meet the requirements of each individual case. In the future, therefore, there should be added emphasis for developing methods for determining the relative minimum data need. RESUME Stabilite, labilite, et instabilite de quelques aspects dun ecosysteme dans les collines nepalese (region de Kakani). Le projet Mountain Hazards Mapping du Nepal National Committee for MAB et de l United Nations University a pour but principal letablissement de cartes de la stabilite des pentes et des dangers naturels au Nepal ainsi que le developpement de methodes devaluation appropriees. Dans la perspective de lUNU-Workshop de septembre 1981 a Berne (themes: Stabilite et instabilite decosystemes de montagne ainsi que Minimum Data Need pour leur evaluation), les connaissances acquises dans la region de Kakani-Kathmandu peuvent etre resumees comme suit: En raison des conditions naturelles (climat de mousson, roche metamorphique fortement alteree, pentes raides), le terrain est generalement labile. Lexploitation agricole intensive accroit le danger de degats irreversibles dans le terrain (par exemple: erosion en profondeur des sols) et de conditions instables dans le sens du Workshop. Dautre part, les agriculteurs fournissent un remarquable input de stabilite par lentretien constant et soigneux des terrasses de culture (en partie irriguees). Cest pourquoi le danger dune instabilite reversible, cest-a-dire qui puisse etre corrigee en lespace dune generation, est generalement taxe deleve, alors que le danger dune instabilite irreversible est estime-du moins dans les conditions actuelles etre relativement faible. Etant donne quil nest pas possible de porter un jugement general sur les donnees minimales a relever et a analyser pour de telles etudes, mais que le besoin de donnees peut varier de cas en cas, il faudrait se concentrer a lavenir sur le developpement de methodes et procedes pour levaluation du besoin minimal de donnees. ZUSAMMENFASSUNG Aspekte der Stabilitiit, Labilitat und Instabilitat eines Oekosystems in der nepalischen Hiigelzone (Kathmandu-Kakani Gebiet). Das Mountain Hazards Mapping Project des Nepal National Committee for MAB und der United Nations University beinhaltet im wesentlichen die Erarbeitung von Karten der Hanglabilitat und Naturgefahren in Nepal sowie die Entwicklung von entsprechenden Beurteilungsmethoden. Die in der Region Kakani-Kathmandu gewonnenen Erkenntnisse lassen sich im Hinblick auf die Themen des UNU-Workshops vom September 1981 in Bern (Stabilitiit und Instabilitait von Gebirgs6kosystemen sowie Minimum Data Need zu deren Beurteilung) folgendermassen zusammenfassen: Wegen der natiirlichen Gegenbenheiten (monsunales Klima, stark verwitterndes metamorphes Gestein, steile Hainge) ist das Terrain generell labil. Die intensive landwirtschaftliche Nutzung erh6ht die Gefahr von irreversiblen Schaden im Terrain (z.B. durch tiefgriindige Bodenerosion) und von instabilen Verhiiltnissen im Sinne des Workshops. Andererseits leisten die Bauern durch die sorgfaltige Pflege der (teilweise irrigierten) Ackerterrassen einen gewaltigen Stabilitaiitsinput. Deshalb wird zwar die Gefahr einer reversiblen, d.h. innerhalb einer Bevolkerungsgeneration korrigierbaren Instabilitaiit generell als hoch, die Gefahr von irreversibler Instabilitaiit aberwenigstens unter den heutigen Bedingungen als relativ gering eingestuft. Weil fur solche Untersuchungen keine allgemeine Aussage fiber die minimal zu erhebenden und auszuwertenden Daten m6glich sind, sondern der Bedarf an Daten ffir jeden Einzelfall anders sein kann, sollte man sich in Zukunft daraufkonzentrieren, Methoden und Vorgangsweisen zur Bestimmung des jeweiligen minimalen Datenbedarfs zu entwickeln. This content downloaded from 207.46.13.134 on Sat, 24 Dec 2016 05:13:55 UTC All use subject to http://about.jstor.org/terms 56 / MOUNTAIN RESEARCH AND DEVELOPMENT