Modelling Landslide Dynamics in Forested Landscapes Promotor: Prof. dr. ir. A. Veldkamp Hoogleraar in de bodeminventarisatie en landevaluatie Laboratorium voor Bodemkunde en Geologie Wageningen Universiteit Co-promotor: Dr. J.M. Schoorl Universitair Docent Laboratorium voor Bodemkunde en Geologie Wageningen Universiteit Samenstelling promotiecommissie (members of the promotion - examination committee): Prof. dr. M.J. Crozier University of Wellington, New Zealand Prof. dr. G. Govers Katholieke Universiteit Leuven, België Prof. dr. T.W.J. Van Asch Universiteit Utrecht, Nederland Prof. dr. ir. L. Stroosnijder Wageningen Universiteit, Nederland Dit onderzoek is uitgevoerd binnen de onderzoekschool C.T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC). Modelling Landslide Dynamics in Forested Landscapes Addressing landscape evolution, landslide soil redistribution and vegetation patterns in the Waitakere Ranges, west Auckland, New Zealand Lieven Claessens PROEFSCHRIFT ter verkrijging van de graad van doctor op gezag van de rector magnificus van Wageningen Universiteit Prof. dr. ir. L. Speelman in het openbaar te verdedigen op vrijdag 22 april 2005 des namiddags te vier uur in de Aula CIP-DATA Koninklijke Bibliotheek, Den Haag Claessens, L., 2005 Modelling Landslide Dynamics in Forested Landscapes. Addressing landscape evolution, landslide soil redistribution and vegetation patterns in the Waitakere Ranges, west Auckland, New Zealand. PhD Thesis Wageningen University, The Netherlands. - With ref. - With summaries in Dutch and English. ISBN 90-8504-145-7 Toitü he whenua, whatungarongaro he tangata (Land is permanent, man disappears) Traditional Maori proverb Is this the real life Is this just fantasy Caught in a landslide No escape from reality © Queen - Bohemian Rhapsody (1975) This research was supported by the Netherlands Organisation for Scientific Research (NWO) under project number 810.62.013. Cover illustration ‘desaggregating the landscape’: 3D representation of the upper part of the Waitakere River Catchment (above the Waitakere Dam). On top is an orthophoto of the area ‘draped’ over a Digital Elevation Model. The three underlying data layers represent (from top down) landslide hazard, elevation and geology. Acknowledgements Looking back at the past four years of work that resulted in this thesis, I really feel privileged for all the chances I’ve got, the inspiring and highly varied working environment and the many colleagues and friends I got to know along the way! I owe a lot of thanks to a lot of people and I apologise to those I might forget. In the first place, I want to thank my promotor Tom Veldkamp: Tom, I really enjoyed the amount of freedom you gave me to gradually come up with the different subjects of research resulting in this little but highly diverse book. The fact that field work areas were a little bit ‘free flowing’ in the beginning, made it necessary to be creative with the original research questions, a process we always managed to accomplish in mutual agreement. This eventually gave me the chance to have a taste of a very broad spectrum of subjects in the fields of geology, geomorphology, soil science and ecology. You also gave me the chance to gain a lot of field experience, building up a database of ‘reference landscapes’ in different and truly interesting parts of the world. Believe me, looking at a landscape will never be the same again, you managed! What made it even more rewarding was the fact that you very often joined me in the field, sharing your own incredible amount of field experience with me (a total of 14 weeks, I counted it!). In addition, my background in geology and landscape processes (and mini-packs and scissors...) was highly enriched when you gave me the opportunity to join the Ishiara fieldwork project in Kenya in 2001. Quite an eye-opener to see the same rocks and landscapes appearing in this quite distant location of New Zealand in 2003! You were right: geologically speaking, it’s a small world…I would be delighted if we can still work together in the future, hopefully also in the field! I also want to thank my co-promotor Jeroen Schoorl. You introduced me to the mighty LAPSUS-world, and helped me making the first steps in programming the landslide component of the model which forms the core of this work. I really appreciated the informal way of exchanging ideas and working together; you were also always very efficient in making helpful comments on premature manuscripts. I very much enjoyed the practical periods in Álora, especially the enthusiasm and hospitality with which you introduced me (and other people) to your true second home. I really hope we can keep developing the LAPSUS framework together and I wish you lots of success in your new Dutch/Spanish home! This work was carried out within the main research programme ‘Podzolisation under Kauri (Agathis australis): for better or worse?’ In this context I want to thank Nico van Breemen for starting and leading this programme in an enthusiastic way, despite the political difficulties regarding study areas we experienced at the start. I also thank Johan Bouma for acting as my first interim promotor in the beginning of the project. I owe a lot of thanks to my ‘kauri- colleagues’ Anne Jongkind and Eric Verkaik. It was not always easy to tune the timing of our different subjects but we did have some nice fieldwork time together in New Zealand. Sharing the house (or rather camping) in Titirangi and ‘Hindersun’ was really cosy and I still wish you both good luck in finishing your kauri research. A lot of work in the Waitakere Ranges was done in co-operation with MSc students who joined me in New Zealand to carry out fieldwork for their theses: Bas, Wouter, Emile, Hans, Ben, Marijn, thanks a lot guys, ‘herders’, for the good work and discussions in the field, for keeping me company during the incredible distances we covered, the exchange of weird music styles, ‘fush ‘n chups’, flat whites and Steinies and the awful KFC moments with mashed potatoes and gravy… The Laboratory of Soil Science and Geology provided an exceptionally nice and friendly working environment and I really enjoyed getting to know a lot of excellent colleagues over the years. I thank Henny and Thea for the valuable administrative and logistic support during the whole process of working in projects and travelling a lot. I especially enjoyed (and still enjoy) the company of the ‘lunch bunch’; work and non-work related issues all passed the scene and this always served as a welcome mid-day break. Absolutely no work related issues at Tuesday’s pub quiz nights though: thanks to the BenG quiz team for these rewarding social events, we rule (provided with some Leffe blond...)! Several people in Wageningen and New Zealand were closely involved in working on some papers included in this thesis. I want to thank Peter Verburg and Gerard Heuvelink (Wageningen), Bruce Hayward (Geomarine Research, Auckland) and David Lowe (Waikato University, Hamilton) for their highly appreciated contributions to several chapters of this thesis. Hopefully we find a way to cooperate on some more interesting subjects in the future. Thanks to Toine Jongmans for the nice company in the field in New Zealand in 2002 and the occasional intro to antique Dutch vases and the historical links between the Netherlands and Belgium. I also very much appreciated the company of Rob van den Berg van Saparoea on various moments and locations in Álora, France and Germany, occasionally accompanied by a good rioja wine and some gambas al pil pil ! Starting as a complete novice in landslide research I appreciated very much the help and advice I got from various colleagues at the universities of Utrecht and Amsterdam: Theo Van Asch, Thom Bogaard, Rens van Beek and Erik Cammeraat, thanks for helping me on the way. Quite some people provided support and advice for carrying out the fieldwork in New Zealand. I want to thank Bruce Burns and Warwick Silvester: your help and advice during the first weeks down under were really appreciated. Rhys Gardner showed us our first kauri tree (less impressive than we thought, it was a seedling…) and has always been very helpful and hospitable during the fieldwork periods in the Waitakere Ranges. Our first and politically rather difficult stay in New Zealand was located in the far north of the North Island; I really enjoyed our stay at the Tree House in Kohukohu in the nice company of the Evans family and Tony Watkins. Tipo, Abraham and Kamira of the Matihetihe Community Development Centre in Mitimiti guided us on a few very (in every sense) breathtaking tramps in the Warawara Forest, cheers mates! When we finally ended up in the Waitakere Ranges, we got the support from Brenda Greene, Scott da Silva and other rangers from the Auckland Regional Council and the Arataki Visitor Centre, Te Kawerau a Maki, the Department of Conservation and Watercare Services Ltd. (Cameron King), this support was very welcome, thanks for that! Our work was also valued by John Edgar from the Waitakere Ranges Protection Society and John Staniland from the Royal Forest and Bird Protection Society kindly gave us permission to work in the Matuku Reserve in Bethells Swamp, Te Henga. During the last months I was able to broaden again my ‘database’ on soils and landscapes, by working in the TOA project in Machakos, Kenya. I want to thank Jetse Stoorvogel for giving me this opportunity and agent Alejandra Mora Vallejo for being part of the excellent fieldwork team that accomplished this ‘mission’. I also spend a lot of time in my car over the last years travelling between Belgium, the Netherlands and France... Besides Lies and my family, there were several other reasons for that: one important one was the fact that I’ve been lucky to play in some very nice bands with very good musicians/friends.