Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Editorial preface to special issue: Temporal and spatial patterns in Holocene floods under the influence of past global change, and their implications for forecasting “unpredecented” future events(Elsevier B.V., 2025-11) Schulte L; Santisteban JI; Fuller IC; Ballesteros-Cánovas JAFloods constitute the most significant natural hazard to societies worldwide. Population growth and unchecked development have led to floodplain encroachment. Modelling suggests that climate change will regionally intensify the threat posed by future floods, with more people in harm's way. From a global change perspective, past flood events and their spatial-temporal patterns are of particular interest because they can be linked to former climate patterns, which can be used to guide future climate predictions. Millennial and centennial time series contain evidence of very rare extreme events, which are often considered by society as ‘unprecedented’. By understanding their timing, magnitude and frequency in conjunction with prevailing climate regime, we can better forecast their future occurrence. This Virtual Special Issue (VSI) entitled Temporal and spatial patterns in Holocene floods under the influence of past global change, and their implications for forecasting “unpredecented” future events comprises 14 papers that focus on how centennial and millennia-scale natural and documentary flood archives help improve future flood science. Specifically, documentation of large and very rare flood episodes challenges society's lack of imagination regarding the scale of flood disasters that are possible (what we term here, the “unknown unknowns”). Temporal and spatial flood behaviour and related climate patterns as well as the reconstruction of flood propagation in river systems are important foci of this VSI. These reconstructions are crucial for the provision of robust and reliable data sets, knowledge and baseline information for future flood scenarios and forecasting. We argue that it remains difficult to establish analogies for understanding flood risk during the current period of global warming. Most studies in this VSI suggest that the most severe flooding occurred during relatively cool climate periods, such as the Little Ice Age. However, flood patterns have been significantly altered by land use and river management in many catchments and floodplains over the last two centuries, thereby obscuring the climate signal. When the largest floods in instrumental records are compared with paleoflood records reconstructed from natural and documentary archives, it becomes clear that precedent floods should have been considered in many cases of flood frequency analysis and flood risk modelling in hydraulic infrastructure. Finally, numerical geomorphological analysis and hydrological simulations show great potential for testing and improving our understanding of the processes and factors involved in the temporal and spatial behaviour of floods.Item Managing at source and at scale: The use of geomorphic river stories to support rehabilitation of Anthropocene riverscapes in the East Coast Region of Aotearoa New Zealand(Frontiers Media S A for American Physical Society, 2023-04-13) Fuller IC; Brierley GJ; Tunnicliffe J; Marden M; McCord J; Rosser B; Hikuroa D; Harvey K; Stevens E; Thomas M; Thoms MRecently uplifted, highly erodible rocks, and recurrent high intensity storms, generate exceedingly high erosion and sedimentation rates in the East Coast Region (Tairāwhiti) of Aotearoa New Zealand. Despite the recent nature of the Anthropocene record in global terms (∼650 years since Māori arrival, 250 years of colonial impacts), human disturbance has profoundly altered evolutionary trajectories of river systems across the region. Here we document catchment-by-catchment variability in anthropogenic signature as geomorphic river stories for five catchments (Waiapu, Hikuwai, Waimatā, Waipaoa, Mōtū). We show how targeted, fit-for-purpose process-based rehabilitation programmes that manage at source and at scale are required to facilitate river recovery in each of these catchments. The largest rivers in the region, Waiapu and Waipaoa, comprise steep, highly dissected terrains that are subject to recurrent hillslope failures, including systemic shallow landslides, occasional deep-seated rotational slumps and earthflows. Localised sediment input from large (>10 ha) gully mass movement complexes overwhelms valley floors. Targeted revegetation programmes are required to reduce extreme sediment inputs from these sources. Although there are fewer gully complexes in the Hikuwai, multiple landslips supply vast volumes of fine-grained sediment that aggrade and are recurrently reworked along channel margins in lowland reaches. Waimatā has no gully complexes and a smaller number of landslips, but large areas are subject to sediment input from earthflows. The terrace-constrained flume-like nature of this system efficiently flushes materials ‘from the mountains to the sea’, recurrently reworking materials along channel banks in a similar manner to the lower Hikuwai. Systematic reforestation in the middle-upper catchment and revegetation of riparian corridors is required to reduce sedimentation rates in these catchments. In contrast, terraces buffer sediment delivery from hillslopes in the upper Mōtū catchment, where a bedrock gorge separates large sediment stores along upper reaches from the lower catchment. As reworking of valley floor sediments in response to bed incision and reworking (expansion) of channel margins is the primary contemporary sediment source in this system, bed control structures and revegetation of riparian corridors are required as part of targeted sediment management plans. We contend that geomorphic river stories provide a coherent platform for Anthropocene rehabilitation strategies that work with the character, behaviour and evolutionary trajectories of river systems. Although this generic lens can be applied anywhere in the world, we highlight particular meanings and implications in Aotearoa New Zealand where such thinking aligns directly with Māori values that respect the mana (authority), mauri (lifeforce) and ora (wellbeing) of each and every riverItem Reanimating the strangled rivers of Aotearoa New Zealand(Wiley Periodicals LLC, 2023-03) Brierley GJ; Hikuroa D; Fuller IC; Tunnicliffe J; Allen K; Brasington J; Friedrich H; Hoyle J; Measures R; Seibert JContemporary management practices have artificially confined (strangled) river systems in Aotearoa New Zealand to support intensified land use in riparian areas. These practices work against nature, diminishing the functionality and biodiversity values of living rivers, and associated socio-cultural relations with rivers. River confinement can accentuate flood risk by promoting development in vulnerable locations and limiting the flexibility to adapt to changing climate, prospectively accentuating future disasters. To date, uptake of space-to-move management interventions that seek to address such shortcomings is yet to happen in Aotearoa New Zealand. This is despite the fact that such practices directly align with Māori (indigenous) conceptualizations of rivers as indivisible, living entities. Treaty of Waitangi obligations that assert Māori rights alongside colonial rights of a settler society provide an additional driver for uptake of space-to-move initiatives. This article outlines a biophysical prioritization framework to support the development and roll out of space-to-move interventions in ways that work with the character, behavior, condition, and evolutionary trajectory (recovery potential) of each river system in Aotearoa.Item Disproportionate and chronic sediment delivery from a fluvially controlled, deep-seated landslide in Aotearoa New Zealand(John Wiley & Sons Ltd, 2022-06-30) McColl ST; Holdsworth CN; Fuller IC; Todd M; Williams FPast research has highlighted the importance of sediment delivery from multiple-occurrence regional landslide events triggered by storms or earthquakes. Herein, we examine delivery from a more persistent source of sediment, that of a large, slow-moving landslide in the soft-rock hill country of Aotearoa New Zealand. We map and monitor the 80-ha Rangitikei Landslide from 2015 to 2019 using time-lapse photography, ground surveys, photogrammetry, and piezometers. We show that the landslide can be divided into several zones with distinctive movement patterns, but all zones respond to river erosion. The fastest zone moves more than 10 m per year in a flow-like fashion, while other zones move 0.01 m per year via slow sliding. Movement occurs all year round, but is two to three times faster in winter and spring. While rainfall and associated groundwater change are commonly attributed to landslide movement patterns, our data show that river flow correlates closely with the weekly to seasonal variability in movement of the landslide toe. This suggests that fluvial erosion can play an important role in the movement dynamics of highly coupled landslides. We estimate an annual sediment yield to the Rangitikei River of at least 40 000 tonnes, in this first quantification of sediment delivery from an active soft-rock landslide in Aotearoa. This volume implies 7% of the total catchment suspended sediment yield is derived from 0.03% of the contributing catchment area, demonstrating the disproportionate effect of this (and likely other) deep-seated landslide(s) as a source of sediment in the Rangitikei catchment. Sediment delivery is more continuous than the episodic supply of multiple-occurrence regional landslide triggering events, and by delivering mostly fine-grained sediment, it has a potentially large impact on water quality.