<p>Typically, integrated coastal zone management (ICZM) uses the informed participation and cooperation of all stakeholders to assess the societal goals in a given coastal area. ICZM seeks, over the long term, to balance environmental, economic, social, cultural and recreational objectives, all within the limits set by natural dynamics. We outline coastal instability in the Auckland region of New Zealand, where the effects of natural coastal dynamics appear to have been underplayed, or even overlooked, during the residential land development process. Auckland is New Zealand&#8217;s largest city, with the Auckland region encompassing c. 3,300 km of coastline, with a highly variable wave climate and coastal geomorphology. The sparsely inhabited high energy west coast records significant wave heights of 2-3 m for much of the year. In contrast, the eastern bay coastlines are lee coasts, protected by offshore islands in the Hauraki Gulf and the Coromandel Peninsula. Nevertheless, significant coastal cliff instability does occur along these eastern coasts, which are heavily populated, with houses often constructed within 10 m of the cliff edge. Coastal instability in the Beachlands area in particular, is part-conditioned by engineering properties of the cliff materials, which include soft, Pleistocene sediments. In particular, shear surfaces develop along clay-rich tephra layers, which are of low-permeability, leading to increased porewater pressure, and cliff failure.&#160; Despite the clear failure mechanisms, coastal protection works and routing of domestic stormwater over the cliffs has led to further coastal instability.</p>
Evidence for the timings of inter-hemispheric climate fluctuations during the Holocene is important, with mountain glacier moraine systems routinely used as a proxy for climate. In New Zealand such evidence for glacier expansion during the late Holocene is fragmentary and is limited to glaciers in a narrow zone within the Southern Alps. Here, we present the first evidence for late-Holocene glacier expansion on the North Island of New Zealand in the form of two unconsolidated debris ridges on the south side of the stratovolcano, Mt Taranaki/Mt Egmont, at ~1920 m a.s.l. The two ridges are aligned north–south along the western and eastern sides of a small basin (Rangitoto Flat), which is formed between the main Taranaki cone (to the north), and the parasitic cone of Fanthams Peak (to the south). The approximate age of the ridges is constrained by dated eruptive events and the relationship between ridge locations and the spatial positioning of adjacent volcanic landforms. We propose the ridges formed as two lateral moraines on the margins of a cirque glacier during the final construction phase of Fanthams Peak between 3.3 and 0.5 ka BP, during late-Holocene time. This time interval accords with published cosmogenic 10 Be dating of moraine-building episodes in the Southern Alps, indicating the Mt Taranaki moraines are a response to the same regional climatic forcings.
The identification and characterisation of faults in urban environments is important to inform seismic and landslide hazard, yet urban development often obscures geological and geomorphological evidence of fault traces. On the other hand, urban development also generates a wealth of borehole data, which, when combined with geophysical surveys, can enable a view into the subsurface. Here we combine geomorphological and geological mapping, gravity surveying, and 3D geological modelling to identify, map and characterise several faults in Beachlands, Auckland, some of which have large offsets. Our work has identified one new fault, the Motukaraka Fault, and confirmed the presence of two proposed faults, the Waikopua North and Te Puru faults. The Motukaraka and Waikopua North faults are both steeply dipping normal faults, which strike NNW and downthrow Mesozoic basement to the west. The Motukaraka Fault has an offset of 250 m (±100 m) and the Waikopua North Fault a combined offset of 240 m (±50 m) across two parallel fault segments. The Te Puru fault strikes northeast near the northern extent of the Waikopua Fault, and downthrows Mesozoic basement to the northwest by 60–100 m. Further investigations are required to determine whether these buried faults are active.
The rock mass rating (RMR) has been used across the geotechnical industry for half a century. In contrast, the coal mine roof rating (CMRR) was specifically introduced to underground coal mines two decades ago to link geological characterization with geotechnical risk mitigation. The premise of CMRR is that strength properties of mine roof rock are influenced by defects typical of coal measures stratigraphy. The CMRR has been used in longwall pillar design, roof support methods, and evaluation of extended cuts, but is rarely evaluated. Here, the RMR and CMRR are applied to a longwall coal mine. Roof rock mass classifications were undertaken at 67 locations across the mine. Both classifications showed marked spatial variability in terms of roof conditions. Normal and reverse faulting occur across the mine, and while no clear relationships exist between rock mass character and faulting, a central graben zone showed heterogeneous rock mass properties, and divergence between CMRR and RMR. Overall, the CMRR data fell within the broad envelope of results reported for extended cuts at Australian and U.S. coal mines. The corollary is that the CMRR is useful, and should not be used in isolation, but rather as a component of a strata control programme.
Seasonal variations in ablation and surface velocity were investigated on the lower part of Fox Glacier, South Westland, New Zealand. A large variation between summer and winter ablation was recorded, with daily averages of 129 mm d−1 and 22 mm d−1, respectively. Variations in measured climatic variables were found to account for ∼90% of variation in ablation during both summer and winter seasons, with significant increases in ablation occurring in conjunction with heavy rainfall events. Surface velocity also showed seasonality, averaging 0.87 m d−1 during summer and 0.64 m d−1 in winter, a reduction of ∼26%. It is thought that the general reduction in velocity during winter can be attributed to a decrease in the supply of surface meltwater to the subglacial zone. Short-term velocity peaks appeared to coincide with heavy rainfall events, with surface velocity responses typically occurring within 24 hours of each rainfall event. During winter, moderate rainfall events (≤100 mm over 24 hours) created a surface velocity response up to 44% greater than the prevailing velocity. Though difficult to deconvolve, magnitudes of surface velocity response to rainfall inputs appear linked to time lags between rainfall events and subglacial drainage efficiency and water storage. The longer-term dynamics of Fox Glacier appear linked to fluctuations in the Southern Oscillation Index (SOI), with positive mass balances of Southern Alps' glaciers appearing to mirror negative SOI (El Niño) conditions. Given the calculated response time of ∼9.1 years for Fox Glacier, the current terminus advance may be linked to mass gains reported in the mid-1990s, with current mass balance gains perhaps leading to terminus advances ∼9 years hence.
Abstract Geomorphologic and sedimentologic investigations in Park Valley, Tararua Range, have identified the presence of a lateral moraine toward the head of the valley. This section of Park Valley is U‐shaped, southwest facing with the elongate ridge situated on the true right (northwestern) side of the valley. A variety of approaches is used to test the possible process origins of the ridge, including topographic and spatial positioning, sedimentology, and paleoclimatic extrapolations. Results indicate the ridge consists of glacial diamict deposited as a lateral moraine, supporting recent hypotheses about late Pleistocene glaciation and erosional development of valleys and cirques of this sector of the range.
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