River form in mountain valleys is the result of the long-term balance between sediment delivery from upstream and lateral sources, and the transfer capability of the river reach. This system feedback is thrown out of equilibrium with the injection of large sediment stores from lateral sources, such as that delivered by a landslide. River response will vary according to the bounding conditions (confinement, floodplain stores), as well as the nature of input materials (mud, sand, gravel, boulders).
By unravelling the chronology of river response to landslides, there is much to learn about the conditions that hold rivers within a particular regime, and the thresholds to be exceeded in order to push them out of it.
New Zealand’s East Coast Region has proven to be an excellent site for the study of river dynamics. The active tectonics, relatively soft and deformed bedrock geology, as well as a dynamic climate and human clearing of the landscape have combined to create conditions for very active river systems.
My research, with colleagues from The University of Auckland, NZ and abroad, has focused mainly on the Waiapu Catchment. This river system is still responding to, and recovering from, very high rates of sediment mobilisation during the course of Cyclone Bola, in 1988. It has been very instructive to examine the mechanisms, connective pathways, and storage zones involved in the transfer of different grain size fractions as they transit from catchment headwaters to the coast. Given the active community interest in monitoring of erosion issues and river management, it has been highly rewarding to develop linkages with stakeholders and local iwi as we assess the potential for future river change.
Tunnicliffe, J. 2017. A sediment budget framework to support river management in Tairāwhiti. Te Mana o Te Wai Tairāwhiti, The Freshwater Conference May 3-4, Uawa – Tolaga Bay.
Tunnicliffe, J., Brierley, G., Fuller, I.C., Leenman, A., Marden, M. and Peacock, D. (2017). Reaction and relaxation in a coarse-grained fluvial system following catchment-wide disturbance. Submitted to Geomorphology.
Walley, Y., Tunnicliffe, J. and Brierley, G. 2017. Network structure and sediment routing in two disturbed catchments, East Cape, New Zealand. Submitted to Geomorphology.
Leenman, A. and Tunnicliffe, J. 2017. Genesis of a major gully mass-wasting complex, and implications for valley filling, East Cape, New Zealand. Submitted to Geological Society of America Bulletin.
Tunnicliffe, J., Leenman, A., Eaton, B. and Fuller, I. (2016). Tracking adjustments in fan and floodplain storage in a braided channel following major sedimentary disturbance, East Cape, NZ. AGU Fall Meeting, Dec. 12-16, San Francisco, CA. Link to Poster
Tunnicliffe, J., Fuller, I., Eaton, B., Peacock, D., Marden, M. (2016). Reconstructing the sediment dynamics of an overloaded gravel bed river, East Cape, N.Z. 11th International Symposium on Ecohydraulics, Feb. 7-12, Melbourne, Australia.
Tunnicliffe, J., Leenman, A. and Reeves, M. (2015). The impacts of landsliding on a gravel bed river network: the remarkable case of New Zealand’s East Cape. Gravel Bed Rivers 8: Gravel Bed Rivers and Disasters. Poster Presentation. Kyoto, Japan, September 15-19, 2015.
Tunnicliffe, J. F. (2014). Integrating new technologies for river topographic surveys and CFD modelling. In The New Zealand Hydrological Society Annual Conference. Blenheim.
Tunnicliffe, J. (2013). The hillslope-channel interface: the influence of debris flows on river channel dynamics. Keynote Talk. IPENZ Rivers Group Annual Symposium, Rotorua, New Zealand 12-13, November, 2013
Tunnicliffe, J. F., & Church, M. (2011). Scale variation of post-glacial sediment yield in Chilliwack Valley, British Columbia. Earth Surface Processes and Landforms, 36(2), 229-243. doi:10.1002/esp.2093
Tunnicliffe, J., and Church, M. (2009). Hillslope-channel coupling in the post-glacial sediment cascade. Invited Talk. American Geophysical Union Fall Meeting, San Francisco, CA December 14-18, 2009.