Master Thesis, Department of Geosciences Landslide Hazard Mapping in Norddal, Møre og Romsdal A case study and review of landslide hazard mapping according to current requirements of the Norwegian Water Resources and Energy Directorate (NVE) Nils Arne Kavli Walberg Landslide Hazard Mapping in Norddal, Møre og Romsdal A case study and review of landslide hazard mapping according to current requirements of the Norwegian Water Resources and Energy Directorate (NVE) Nils Arne Kavli Walberg Master Thesis in Geosciences Discipline: Environmental Geology and Geohazards Department of Geosciences Faculty of Mathematics and Natural Sciences University of Oslo [30 ECTS] st June 1 2013 © Nils Arne Kavli Walberg, 2013 Supervisors: Andrea Taurisano (NVE) and Valerie Mauphin (UiO) This work is published digitally through DUO – Digitale Utgivelser ved UiO http://www.duo.uio.no It is also catalogued in BIBSYS (http://www.bibsys.no/english) All rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, without permission Front page photo: Outer part of the Norddal village, taken from SE (photo: M. Lund) Abstract Landslide hazard mapping in Norway today is usually performed by external consulting companies on behalf of the Norwegian Water Resources and Energy Directorate (NVE), resulting in varying level of mapped details and interpretation of guidelines. The focus of this study has been existing methodology within landslide hazard mapping, and the aim of the project is to evaluate its appropriateness within current landslide hazard mapping. To do this, a complete landslide hazard mapping assessment is conducted for Norddal in Møre og Romsdal, and the methodology used are thoroughly explained and discussed. Norddal was chosen as it was assigned 1st priority regarding rock fall and snow avalanche hazard, and 2nd priority regarding debris slide and debris flow hazard in an initial national mapping of landslide prone areas conducted by NVE. The methodology includes determination of a landslide inventory map, meteorological investigations related to landslide and snow avalanche initiation, topographical studies and run out modeling, where the later is emphasized. Six different models were performed to determine run out; the α,β-model for both snow avalanches and rock falls, RocFall and Rockyfor3D for rock falls, and AVAL-1D and RAMMS for snow avalanches. They range from simple empirical models based on the height of a cliff, to more complex numerical simulations that require extensive input. All methods used were found suitable and provided important information to the mapping project, where the main challenge was considered the adaption of the obtained information to the recurrence intervals stated in the regulations. Four hazard maps were produced from the available information, calculations and field work for each of the mass movement types: rock falls, snow avalanches and debris slides, and one for the total hazard which should be used in land use planning. The rating of the different methods used in the preparation of the extent of the hazard zones are thoroughly explained, together with advantages and disadvantages of the different methods. The kind of methods which could be applied under different conditions and how their results can be interpreted regarding different hazard zones is considered the main focus of this project. This information may be applied to future guidelines for landslide hazard mapping in Norway. I Sammendrag Skredfarekartlegging i Norge blir i dag i stor grad utført av eksterne selskaper på oppdrag fra Norges vassdrags- og energidirektorat (NVE), noe som fører til varierende tolkning av retningslinjer og detaljnivå. Målet med denne oppgaven er å evaluere de mest vanlige metodene innen skredfarekartlegging i Norge i dag, og å diskutere fordeler, ulemper og utfordringer knyttet til disse metodene. Dette er gjort gjennom en detaljert farekartlegging i Norddal, Møre og Romsdal, hvor områder utsatt for snøskred, steinsprang, jord- og flomskred er kartlagt. Norddal er valgt som studielokalitet på grunn av at området ble rangert som 1.prioritet for kartlegging av snøskred- og steinsprangfare, samt 2. prioritet i forhold til jordskred og flomskredfare i innledende skredfarekartleggingsundersøkelser utført av NVE. Metodene som er brukt inkluderer utarbeidelsen av et hendelseskart basert på tidligere skred i området, undersøkelser av lokale meteorologiske forhold som kan påvirke utløsning av skred, topografiske studier og modellering av utløpslengder for ulike skredtyper. Spesielt sistnevnte er vektlagt stor betydning og seks ulike modeller er benyttet til simuleringer av utløpsdistanse; α,β-modellen for snøskred og steinsprang, RocFall og Rockyfor3D for steinsprang, samt AVAL-1D og RAMMS for snøskred. Modellene strekker seg fra enkle, empiriske modeller som tar utgangspunkt i høyden til fjellsiden, til mer kompliserte dynamiske modeller som krever mer og detaljert bakgrunnsinformasjon. Alle metodene har vist seg nyttige og tilført viktig informasjon i kartleggingsarbeidet, hvor hovedutfordringen har vært å koble sammen resultater fra metodene til gjentaksintervallet som faresonene bygger på. Fire ulike skredfarekart er utarbeidet, ett for hver av de tre ulike skredtypene og ett for den totale faren, hvor sistnevnte skal brukes innen arealplanlegging. Grunnlaget for utstrekningen til de ulike faresonene er grundig forklart, det samme gjelder utfordringer knyttet til de ulike metodene. Hvilke metoder som kan anvendes og hvordan resultatene fra disse kan settes i sammenheng med de ulike faresonene vurderes som det viktigste resultatet i denne oppgaven, noe som kan brukes i et kommende arbeid angående retningslinjer innen skredfarekartlegging i Norge. II Acknowledgments This work is made possible by the collaboration of the University of Oslo (UiO) and the Norwegian Water Resources and Energy Directorate (NVE). Several people deserve to be thanked. First, I would like to express my gratitude to my supervisor, Andrea Taurisano (NVE). Thank you for introducing me to the field of landslide hazard mapping, for all rewarding meetings at NVE and your encouraging advices in an otherwise busy schedule. I would also thank my co- supervisor, Valerie Mauphin (UiO) for useful contribution to the final outline of the thesis. I would also like to thank all the people within the Norwegian scientific environment which have helped me out with the different issues I have questioned – thank you! An extra thanks goes to Luzia Fischer at the Geological Survey of Norway (NGU) for valuable insight in and discussions about their ongoing project about debris flow susceptibility mapping. Judith Wells-Walberg, I am incredible grateful for you proofreading my thesis! I am very glad you did not back down when my thesis inexplicably doubled in size from the aforementioned 60 pages. You have really learned me a lot about grammar! Thanks to my family which always has been there for me and my fellow students for interesting discussions and nice friendship the last five years! I hope we will stay in touch after the graduation as well! The biggest thank goes to my girlfriend Monika. Despite writing your own thesis, you have always answered my questions and provided me new approaches during discussions. I am very grateful for knowing you! Nils Arne Blindern, 01.06.2012 III Table of contents 1 INTRODUCTION ..................................................................................................................... 1 1.1 BACKGROUND ......................................................................................................................... 1 1.2 PURPOSE OF STUDY ................................................................................................................. 3 2 TERMINOLOGY AND PROCESS TYPES ........................................................................... 4 2.1 TERMINOLOGY ........................................................................................................................ 4 2.2 PROCESS TYPES ....................................................................................................................... 6 2.2.1 Rock falls and rock avalanches .................................................................................... 6 2.2.2 Flows and slides in soil ................................................................................................ 8 2.2.3 Snow avalanches ........................................................................................................ 11 3 GOVERNMENTAL REGULATIONS .................................................................................. 13 4 STUDY AREA ......................................................................................................................... 15 4.1 GEOGRAPHY .......................................................................................................................... 15 4.2 CLIMATOLOGY ...................................................................................................................... 16 4.3 GEOLOGY .............................................................................................................................. 17 4.3.1 Bedrock geology ......................................................................................................... 17 4.3.2 Quaternary geology.................................................................................................... 18 4.4 VEGETATION ........................................................................................................................