Hawke's Bay Region Research Articles

Spatial Variation of Shallow Stress Orientation Along the Hikurangi Subduction Margin: Insights From In‐Situ Borehole Image Logging

AbstractKnowledge of the contemporary in‐situ stress orientations in the Earth's crust can improve our understanding of active crustal deformation, geodynamic processes, and seismicity in tectonically active regions such as the Hikurangi Subduction Margin (HSM), New Zealand. The HSM subduction interface is characterized by varying slip behavior along strike, which may be a manifestation of combined variations in both stress state and the mechanical properties of faults and their hanging walls. Alternatively, these variations in subduction thrust slip behavior may drive heterogeneity in the stress state in space and time. In this study, we analyze borehole image and oriented four‐arm caliper logs acquired from 13 boreholes along the HSM to present a comprehensive stress orientation data set from borehole data within the shallow (<3 km) upper plate of the subduction thrust. Our results reveal a 065°/245° SHmax orientation within the central HSM (Hawke's Bay region) which rotates to 112°/292° and 140°/320° in the southern HSM. This rotation of SHmax orientation correlates spatially with along‐strike variations in subduction interface slip behavior, characterized by creep and/or shallow episodic slip events in the central HSM and interseismic locking in the south. The borehole SHmax orientations suggest that contemporary stress orientations may be caused in part by along‐strike variation in deformation style imposed by clockwise rotation of forearc. In the southern HSM, borehole‐derived SHmax orientations are inconsistent with SHmax orientations derived from focal mechanism solutions in the subducting plate, implying some degree of mechanical decoupling between the shallow hanging wall and subducting slab.

Has the introduction of two subspecies generated dispersal barriers among invasive possums in New Zealand?

The introduction of species into new environments provides the opportunity for the evolution of new forms through admixture and novel selection pressures. The common brushtail possum, Trichosurus vulpecula vulpecula from the Australian mainland and T.v.fuliginosus from Tasmania, were introduced multiple times to New Zealand from Australia to become one of New Zealand’s most significant pests. Although derived from two subspecies, possums in New Zealand are generally considered to be a single entity. In a previous analysis, we showed that possums in the Hawkes Bay region of New Zealand appeared to consist of at least two overlapping populations. Here, we extend that analysis using a genotype-by-sequencing approach to examine the origins and population structure of those possums and compare their genetic diversity to animals sampled from Australia. We identify two populations of each subspecies in Hawkes Bay and provide clear evidence of a contact zone between them in which a hybrid form is evident. Our analysis of private alleles shows higher rates of dispersal into the contact zone than away from it, suggesting that the contact zone functions as a sink (and hence as a barrier) between the two subspecies. Given the widespread and overlapping distribution of the two subspecies across both large islands in New Zealand, it is possible that many such contact zones exist. These results suggest an opportunity for a more targeted approach to controlling this pest by recognising sub-specific differences and identifying the contact zones that may form between them.

Effect of inter-annual variability in pasture growth and irrigation response on farm productivity and profitability based on biophysical and farm systems modelling

Farm system and nutrient budget models are increasingly being used in analysis to inform on farm decision making and evaluate land use policy options at regional scales. These analyses are generally based on the use of average annual pasture yields. In New Zealand (NZ), like in many countries, there is considerable inter-annual variation in pasture growth rates, due to climate. In this study a modelling approach was used to (i) include inter-annual variability as an integral part of the analysis and (ii) test the approach in an economic analysis of irrigation in a case study within the Hawkes Bay Region of New Zealand.The Agricultural Production Systems Simulator (APSIM) was used to generate pasture dry matter yields (DMY) for 20 different years and under both dryland and irrigation. The generated DMY were linked to outputs from farm-scale modelling for both Sheep and Beef Systems (Farmaxx Pro) and Dairy Systems (Farmax® Dairy Pro) to calculate farm production over 20 different years. Variation in DMY and associated livestock production due to inter-annual variation in climate was large, with a coefficient of variations up to 20%. Irrigation decreased this inter-annual variation. On average irrigation, with unlimited available water, increased income by $831 to 1195/ha, but when irrigation was limited to 250mm/ha/year income only increased by $525 to 883/ha. Using pasture responses in individual years to capturing the inter-annual variation, rather than the pasture response averaged over 20years resulted in lower financial benefits. In the case study income from irrigation based on an average year were 10 to >20% higher compared with those obtained from individual years.

Fifteen into Three Does Go: Morphology, Genetics and Genitalia Confirm Taxonomic Inflation of New Zealand Beetles (Chrysomelidae: Eucolaspis)

Eucolaspis Sharp 1886 is a New Zealand native leaf beetle genus (Coleoptera: Chrysomelidae: Eumolpinae) with poorly described species and a complex taxonomy. Many economically important fruit crops are severely damaged by these beetles. Uncertain species taxonomy of Eucolaspis is leaving any biological research, as well as pest management, tenuous. We used morphometrics, mitochondrial DNA and male genitalia to study phylogenetic and geographic diversity of Eucolaspis in New Zealand. Freshly collected beetles from several locations across their distribution range, as well as identified voucher specimens from major museum collections were examined to test the current classification. We also considered phylogenetic relationships among New Zealand and global Eumolpinae (Coleoptera: Chyrosomelidae). We demonstrate that most of the morphological information used previously to define New Zealand Eucolaspis species is insufficient. At the same time, we show that a combination of morphological and genetic evidence supports the existence of just 3 mainland Eucolaspis lineages (putative species), and not 5 or 15, as previously reported. In addition, there may be another closely related lineage (putative species) on an offshore location (Three Kings Islands, NZ). The cladistic structure among the lineages, conferred through mitochondrial DNA data, was well supported by differences in male genitalia. We found that only a single species (lineage) infests fruit orchards in Hawke’s Bay region of New Zealand. Species-host plant associations vary among different regions.

A unique species of Mecodema (Carabidae: Broscini) from the Hawke's Bay region, New Zealand, with implications for North–South Island zoogeography

Mecodema chaiup sp. nov. (Carabidae: Broscini) is described from a single male specimen collected from Mohi Bush Scenic Reserve, Maraetotara Plateau, Hawke's Bay, New Zealand. The species is unique among Mecodema in that its elytra are narrower than the pronotum at the widest point. Based on body size and elytral configuration this species could represent the first member of the ‘costellum species group’ found in the North Island. Alternatively, aedeagal and head configuration support a close phylogenetic relationship with the widespread M. oconnori.http://zoobank.org/urn:lsid:zoobank.org:pub:ACFCBAC9-9013-4F1B-9FCE-09F2CE79DC70

Native flora and fauna response to removal of the weed Hydrilla verticillata (L.f.) Royle in Lake Tutira

Hydrilla has been in New Zealand since the 1960s and formed major infestations in four lakes in the Hawkes Bay region. Challenges to controlling hydrilla in New Zealand have included a lack of tools and the changing responsibilities of local management agencies. A grass carp field trial was initiated in 1988 in the smallest of the hydrilla infested lakes to assess the feasibility of eradicating hydrilla. After the main hydrilla beds were consumed, regrowth from tubers still occurred for a further 12 years. In 2008, grass carp were released into the remaining three hydrilla-infested lakes in a central government led response to eradicate hydrilla. This paper describes the changes in the flora and fauna in the largest of these lakes, Lake Tutira, following the introduction of grass carp and the removal of the hydrilla weed beds. Annual surveys of aquatic vegetation and macroinvertebrates in the lake from 2008 to 2012 have shown that, following the removal of the hydrilla weed beds by 2010, there was a shift in grass carp grazing to marginal emergent plants, and a general increase in the distribution of the native plant vegetation, although there was some evidence of a decline in charophyte abundance. Macroinvertebrate diversity was maintained although there were changes in the relative abundance of taxa linked to changes in the littoral vegetation.

Service Quality Perception and Satisfaction in a New Zealand Festivalscape: Buying Behavior Effects

This study identified three festivalscape dimensions, namely generic festival features, specific events and comfort amenities, and entertainment features, as indicators of quality perception. A strong relationship between the quality perception and satisfaction constructs could not be found, similar to other studies. The study was conducted on 389 attendees at a major wine festival in the Hawke's Bay Region of New Zealand. The research provides new insight to festivalscape knowledge in that it identifies the first-time and repeat visitor dynamic as a predictor of actual buying behavior at a festival. The higher the percentage of repeat visitors, the higher the likelihood of (wine) buying. The festival's entertainment features are a stronger predictor of buying behavior than generic festival features or specific events and comfort amenities. Repeat visitors, 35 years and older in age, are the highest yielding visitor group from a financial viewpoint. First-time visitors are far more short-term oriented than repeat visitors in their planning when making the final decision to attend the festival event.

Customers of place: exploring interregional migrant collectivities

PurposeThe aim of this research is to explore how and why different migrant groups see different values in places they move to. Understanding these values and also the conditions in which these values are shaped will help in targeting marketing effort.Design/methodology/approachThe hierarchical and K‐means cluster analyses were instrumental in identifying different migrant clusters. Planned contrasts were employed to compare related pairs of clusters. The logistic regression analysis identified several determinants of cluster membership likelihood.FindingsFour different internal migrant clusters are identified in the Hawke's Bay region of New Zealand. These are Material Success Seekers, Community/Environment Folks, Apathetics, and All‐rounders. The former two express a fragmentalist lifestyle. Material Success Seekers emphasise regional business opportunities while being indifferent to social and natural resources. In contrast, Community/Environment Folks emphasise social and natural resources while maintaining indifference to business opportunities. In turn, the latter two clusters make up a holistic lifestyle: All‐rounders consider all three major characteristics of the region to be important while apathetics totally deemphasise these characteristics. The planned contrasts show that demographics are instrumental in predicting differences between related clusters but not helpful in distinguishing the identified lifestyles.Research limitations/implicationsThe limitation of this investigation is that the important constructs used to cluster migrants are not well calibrated, although the reliability scores appear to be satisfactory. Moreover, the use of four‐point importance scales does not allow attaining a greater level of construct sensitivity. The research method is unique in a sense that the cluster analysis and the planned contrasts are applied to examine contrasting values of migrant collectivities.Practical implicationsA number of specific practical challenges need to be resolved by the regional decision makers in order to enhance place satisfaction by internal migrant collectivities. First, the regional and city councils will need to tailor different services, facilities, and public spaces to appeal to different requirements of migrant clusters. Second, the region's settlement support agency should provide migrants with relevant, focused, and differentiated information about available services and resources to suit their various life goals, aspirations, and values.Originality/valueThis investigation tackles the problem of lacking theoretical and empirical research foundation on internal migration as a marketing phenomenon. Moreover, it is unique in its approach of conceptualising migrant segments as cultural phenomena, that is, interdependent collectivities that form on the basis of contrasting values.

Contesting Property Development in Coastal New Zealand: A Case Study of Ocean Beach, Hawke's Bay

AbstractThis article considers the contested process of coastal development in New Zealand and the implications of both governmental regulation and public concern for understanding property. Its empirical focus is a proposal for a substantial, new urbanist development at Ocean Beach, located in the Hawke's Bay region of the North Island. Three key sources of data inform the research: published reports; public submissions to council; and interviews with a sample of those involved in the planning process. Opposition to development is explained in terms of three broad areas of concern: the dramatic physical and social changes that would accompany subdivision and construction; fears of a loss of control over a valued local landscape; and a morally informed sense of propriety. The article finds that the ownership model of property is not especially powerful at Ocean Beach; rather, there is a broad consensus that private property rights exist within a public planning framework. It is this framework that contributes, in large part, to ensuring that voices of community opposition to property development at Ocean Beach (and elsewhere along the coast) are heard. Nevertheless, private property rights are rarely dismissed completely.Résumé Cet article porte sur une démarche contestée d'aménagement côtier en Nouvelle‐Zélande, ainsi sur les incidences de la réglementation gouvernementale et de l'inquiétude de la population, pour mieux comprendre le sens de la propriété. Sur le plan empirique, il s'intéresse à une vaste urbanisation nouvelle proposée sur le site d'Ocean Beach situé dans la région de Hawke's Bay dans l'île du Nord. L'étude tire ses données de trois sources principales: rapports publiés, soumissions publiques auprès du conseil, et entretiens avec un groupe représentatif de personnes impliquées dans le processus d'aménagement. L'opposition au complexe s'articule autour de trois grands domaines de préoccupation: les changements physiques et sociaux radicaux qu'occasionneraient subdivision et construction; les craintes de perdre la maîtrise d'un paysage local prisé; un sens de la propriété reposant sur des valeurs morales. Le modèle de propriété immobilière ne s'impose pas particulièrement à Ocean Beach; on y trouve plutôt un large consensus pour que les droits de propriété privée existent dans un cadre d'aménagement public. C'est ce cadre qui contribue en grande partie à garantir que soient entendues les voix de la communauté opposées à l'aménagement immobilier d'Ocean Beach (ou sur tout autre site côtier). Néanmoins les droits de propriété privée sont rarement complètement rejetés.

Effects of pre-harvest foliar calcium sprays on fruit calcium levels and brown rot of peaches

Brown rot of stonefruits caused by Monilinia fructicola (Wint.) Honey continues to be responsible for significant crop losses in New Zealand despite the application of recommended fungicides. The goal of our research programme is to substantially improve brown rot management and in the first part of a multi-year programme, we investigated the hypothesis that supplementing a brown rot fungicide spray programme with calcium (Ca) reduces brown rot incidence. A range of commercially available Ca products were applied to peach ( Prunus domestica L.) trees (cv. ‘Scarlett O’Hara’) at two weekly intervals from 3–5 November until fruit harvest (January 2001 and 2002) in the Hawke's Bay region of New Zealand. Calcium content of the peach epidermis was significantly increased by at least 50% by Ca sprays, compared to unsprayed fruit in both seasons. Increasing the Ca content of fruit significantly reduced the incidence and severity of M. fructicola infections in fruit disk assays. Pre-harvest Ca applications also significantly reduced the number of brown rot infected fruit per tree at harvest and the incidence of postharvest rots. The integration of Ca foliar sprays into current brown rot management practices has been widely adopted by stone fruit growers in New Zealand as a practical tool to reduce brown rot losses.

Regional classification of New Zealand red wines using inductively-coupled plasma-mass spectrometry (ICP-MS)

Red wines in a dataset of 120 single-region wines could be classified into seven of the major New Zealand winegrowing regions with an overall accuracy of 80.8% using leave-one-out linear discrimination with the elements Sr, Rb, Ni, Co, Pb, Mn, Cd, Ga and Cs. A higher classification accuracy of 94.4% was achieved when regions were combined into North Island, Nelson, and other South Island regions. The rare earth elements did not prove useful for regional classification, both because of their low and variable concentrations and because their concentrations can be increased upon bentonite fining. Wines originating in the Gimblett Gravels Winegrowing District could be discriminated from wines grown in the remainder of the Hawke's Bay region with a high degree of accuracy using Ba, Cs, Rb, and Pb. A small difference in elemental composition between Pinot Noir, Cabernet Sauvignon, and Merlot wines originating from the Hawke's Bay region was observed. However, despite this difference greater classification accuracy was obtained with a database containing all the red wines than a subset containing only Pinot Noir wines.

Pulsed-field gel electrophoresis of Campylobacter jejuni sheep abortion isolates

Campylobacter species are a significant cause of sheep abortion in most sheep-raising countries. In New Zealand, Campylobacter fetus subsp. fetus is the leading cause of diagnosed sheep abortion and the species C. jejuni and C. coli have also been implicated. To date, strain typing information of C. jejuni sheep abortion isolates is limited. The objective of the present study was to genotype C. jejuni isolates cultured from sheep abortions submitted to diagnostic laboratories in New Zealand during the 2000 breeding season, using pulsed-field gel electrophoresis (PFGE). In this study, C. jejuni isolates were cultured from approximately 10% of farms from which Campylobacter species were isolated from sheep abortions in the year 2000. This equated to 25 C. jejuni isolates from 21 farms. These isolates were obtained from the veterinary diagnostic laboratories and strain typed using the molecular typing technique PFGE. Ten distinct PFGE types were identified amongst the isolates. No particular PFGE type was found most frequently amongst these C. jejuni sheep abortion isolates. However, indistinguishable or similar C. jejuni PFGE types were identified from different aborted foetuses from the same flock, consistent with the role of C. jejuni as an infectious cause of abortion in sheep. These strain types were similar or indistinguishable from C. jejuni sheep abortion isolates obtained in 1999 in a smaller study (Mannering, S.A., Marchant, R.M., Middelberg, A., Perkins, N.R., West, D.M., Fenwick, S.G., 2003. Pulsed-field gel electrophoresis typing of C. fetus subsp. fetus from sheep abortions in the Hawke's Bay region of New Zealand. NZ Vet. J. 51, 33–37).

Ash fall prediction in New Zealand

The North Island of New Zealand contains seven active volcanoes or volcanic centres, and ash fall from these centres could present health hazards and other problems. Part of the required contingency planning for ash fall is the assessment of the frequency and depth of ash fall at any point. The issue is particularly important for urban areas likely to be affected. This paper develops a theory for ash fall frequency assessment based on estimated eruption frequencies and magnitudes and on meteorological data. The theory is used to obtain the ash fall frequency/depth relationship for the Napier /Hastings area in the Hawkes Bay region. The results show that the annual frequency of significant ash fall in the towns is high enough to justify some degree of emergency preparedness, with a fall of 1 mm having an annual exceedance probability of about 0.05, or in other words a return period of approximately 20 years.

Pulsed-field gel electrophoresis typing of Campylobacter fetus subsp. fetus from sheep abortions in the Hawke's Bay region of New Zealand

AIM: To type Campylobacter isolates from sheep abortions from the Hawke's Bay region of New Zealand. METHODS: Campylobacter isolates were collected from aborted sheep foetuses from commercial farms in the Hawke's Bay region. Information on the Campylobacter vaccination status of flocks in the study was collected. Isolates were identified to species level using standard phenotypic tests, then typed using pulsed-field gel electrophoresis (PFGE). RESULTS: Eighty-one C. fetus subsp. fetus isolates were cultured from aborted sheep foetuses from 25 farms and four C. jejuni isolates were cultured from foetuses from three farms. The C. fetus subsp. fetus isolates were classified into six PFGE groups. A single pulsed-field type predominated amongst isolates from 19 of the 25 farms. The C. jejuni isolates comprised two types. CONCLUSIONS: A range of C. fetus subsp. fetus PFGE types was identified, and one type, B1, was found most frequently. Campylobacter fetus subsp. fetus was only isolated from samples from sheep that had not been vaccinated with C. fetus subsp. fetus vaccine that season.

Variability in establishing white clover in pastures on farms

Reported problems with inconsistent white clover establishment in pastures prompted a MAF SFF project to investigate the causes. The establishment of white clover in 32 new and renovated paddocks on 16 farms in the Wanganui-Manawatu-Southern Hawke's Bay region was monitored and the inconsistency confirmed in the f irst year. Seedling emergence at 44% (range 22 to 84) for ryegrass and 35% (range 9 to 73) for white clover was low (expected 70%+) and inappropriate grazing management inhibited subsequent plant growth and sward performance to 20% of potential. There were a few good performances, but the 'grass to grass' technique was particularly hard on clover. These problems have arisen as a result of modern methods (e.g. direct drilling and fertiliser N) that are less 'clover friendly', and have moved away from the older proven techniques. Minimal seedbed preparation and method of sowing, combined with lack of knowledge of white clover growth strategies and management requirements are seen as the main causes. Change is inescapable and while modern farming techniques and expectations may have currently placed clover at a disadvantage, the challenge now is how to balance the requirements of the pasture species with the expectations of the farming production system in the future. Keywords: emergence, establishment, farmer knowledge, grazing management, life cycle, sowing conditions, white clover.

Serious health events following involuntary job loss in New Zealand meat processing workers.

The association between unemployment and poor health outcomes is well documented. Significant debate exists as to whether unemployment causes ill health or whether those with poor health find it harder to obtain and maintain employment. Factory closure studies are well placed to comment on causation. The objective of this study was to investigate associations between involuntary job loss, mortality and serious illness. An 8-year follow-up of workers from two meat-processing plants in the Hawkes Bay region of New Zealand. A cohort (n = 1945) made redundant in 1986 was compared with a cohort (n = 1767) from the neighbouring plant that remained open until 1994. Incidence rates for mortality, cancer registrations and admissions to public hospitals were derived from record linkage with routinely collected national data. Follow-up for the period 1986-1994 was 96% complete for both plants. Among the cohort made redundant in 1986, there was an increased risk of serious self-harm which led to hospitalization or death (adjusted for age, sex and ethnicity relative risk [RR] = 2.47; 95% CI: 1.04-5.89) compared to the employed cohort. The RR of admission to hospital with a mental health diagnosis was 1.17 (95% CI: 0.68-2.01). There were no other statistically significant findings. This study has most of the features of an 'ideal' factory closure study, in that it achieved near-complete follow-up of a large workforce made redundant and a similar employed workforce for 8 years. We found that exposure to involuntary job loss increased the risk of mental distress leading to serious self-harm. No other association was found.

An integrated hydrological model for rain‐induced landslide prediction

AbstractThis paper describes an extension to the Combined Hydrology And Stability Model (CHASM) to fully include the effects of vegetation and slope plan topography on slope stability. The resultant physically based numerical model is designed to be applied to site‐specific slopes in which a detailed assessment of unsaturated and saturated hydrology is required in relation to vegetation, topography and slope stability. Applications are made to the Hawke's Bay region in New Zealand where shallow‐seated instability is strongly associated with spatial and temporal trends in vegetation cover types, and the Mid‐Levels region in Hong Kong, an area subject to a variety of landslide mechanisms, some of which may be subject to strong topographic control. An improved understanding of process mechanism, afforded by the model, is critical for reliable and appropriate design of slope stabilization and remedial measures. Copyright © 2002 John Wiley & Sons, Ltd.

Resedimentation of the 1.8 ka Taupo ignimbrite in the Mohaka and Ngaruroro river catchments, Hawke's Bay, New Zealand

Deposition of the 1.8 ka Taupo ignimbrite in the Hawke's Bay buried parts of the Ngaruroro and Mohaka River catchments beneath up to 40 m of loose pyroclastic debris. Re‐establishment of the two river systems led to the remobilisation of the loose debris and followed similar patterns in both catchments. An initial period of laharic remobilisation and formation of lahar‐deposit‐dammed lakes was followed by two phases of fluvial remobilisation. During the first of these, streams were shallow and ephemeral to perennial, with sediment‐laden flash‐floods eroding headwards through valley‐ponded primary pyroclastic and laharic deposits. With gradual re‐establishment of vegetation, the sediment:water ratio decreased, and braided rivers with deeper, more stable channels became dominant. Although the general pattern of resedimentation was similar for both river systems, field evidence shows that the volumes of remobilised material, and the likely durations of resedimentation in the different catchments, differed. These variations reflect: (1) the different volumes of initial ignimbrite in the trunk valleys; (2) the different percentage of catchment areas covered by ignimbrite debris; and (3) the different river gradients and valley shapes. However, extremely high sediment yields in the Hawke's Bay region are estimated to have persisted for at least 4–17 yr after the eruption.

Earthquake triggering in the Hawke's Bay, New Zealand, region from 1931 to 1934 as inferred from elastic dislocation and static stress modeling

During the 1930s the Hawke's Bay region of New Zealand experienced four large earthquakes, Napier (MW 7.6) and Hawke Bay (MW 7.3) in 1931, Wairoa (MW 6.9) in 1932, and Pahiatua (MW 7.4) in 1934. We address the question of whether these comprise a triggered sequence of events. There are significant difficulties in dealing with earthquakes that were recorded 70 years ago as fault parameters are difficult to obtain. With the exception of the Pahiatua earthquake, no primary surface fault ruptures were identified, and locations for the other three events may be in error by tens of kilometers. However, geodetic data were collected before and after the Napier and Wairoa earthquakes, and regions of uplift and subsidence from the former have been mapped from low‐order leveling data. This information helps to constrain the fault parameters for the first of these events through elastostatic modeling. Results from recent teleseismic body wave modeling have been used to determine fault parameters for the Hawke Bay event. Our analysis of the induced static stresses with the Coulomb failure criterion shows that the Napier earthquake triggered both the Hawke Bay and Wairoa earthquakes but that the Hawke Bay earthquake probably delayed the Wairoa earthquake. We also conclude that these three events did not trigger the Pahiatua earthquake.

Environmental response to a large, explosive rhyolite eruption: sedimentology of post-1.8 ka pumice-rich Taupo volcaniclastics in the Hawke's Bay region, New Zealand

The 1.8 ka eruption of the Taupo ignimbrite from the Taupo Volcanic Centre in the central North Island of New Zealand produced a ∼30 km 3 ignimbrite covering an area ca. 160 km in diameter, centred on Lake Taupo. Remobilisation of its pyroclastic detritus triggered major alluviation in the years to decades after its emplacement. In the Hawke's Bay region in the eastern North Island, three large rivers rise in the ignimbrite-impacted mountainous headwaters, in areas that were buried by up to 40 m of loose, unconsolidated pumiceous material. Analysis of preserved volcaniclastic sediments along valleys shows that resedimentation occurred in two main stages characterised by contrasting sediment:water ratios. The first comprised erosion and redeposition of ignimbrite debris by lahars, e.g. debris flows and hyperconcentrated flows. The second was marked by decreasing sediment:water ratios and the re-establishment of braided fluvial systems in the former river valleys, as recorded by such deposits as trough, planar, low-angle and antidune cross-bedded, planar-bedded, and ripple cross-laminated sands and gravels. However, there is no systematic chronological trend towards lower pumice contents in these fluvial facies. Four characteristic sets of co-occurring lithofacies were produced during the sedimentary response: (1) Laharic remobilisation association; (2) Upper-flow regime-dominated stream-flow association; (3) Lower-flow regime-dominated stream-flow association; and (4) Lacustrine association. Individual lithofacies were strongly controlled by the unusual hydrodynamic properties of pumice, particularly its low and variable density. Automated settling tube analysis of water-saturated pumiceous sediment confirms that sieve analysis is misleading with respect to the hydrodynamic behaviour of such sediments. Recasting granulometric data in terms of effective hydraulic grain size shows better sorting of mixed component sediments, but statistical sorting and mean grain-size parameters do not discriminate between the deposits of tractional and overcapacity parent flows. Therefore, particle behaviour is addressed by using both lithofacies and petrofacies in the description and classification of the remobilisation deposits.