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71.
This paper introduces a generic framework for multi-risk modelling developed in the project ‘Regional RiskScape’ by the Research Organizations GNS Science and the National Institute of Water and Atmospheric Research Ltd. (NIWA) in New Zealand. Our goal was to develop a generic technology for modelling risks from different natural hazards and for various elements at risk. The technical framework is not dependent on the specific nature of the individual hazard nor the vulnerability and the type of the individual assets. Based on this generic framework, a software prototype has been developed, which is capable of ‘plugging in’ various natural hazards and assets without reconfiguring or adapting the generic software framework. To achieve that, we developed a set of standards for treating the fundamental components of a risk model: hazards, assets (elements at risk) and vulnerability models (or fragility functions). Thus, the developed prototype system is able to accommodate any hazard, asset or fragility model, which is provided to the system according to that standard. The software prototype was tested by modelling earthquake, volcanic ashfall, flood, wind, and tsunami risks for several urban centres and small communities in New Zealand.  相似文献   
72.
The Thame is one of the principal left-bank affluents of the Thames, the largest river in southern England; it joins the Upper Thames at Dorchester, ∼20 km downstream of Oxford. Its terraces include a younger group of four, which date from the late Middle Pleistocene and Late Pleistocene, are disposed subparallel to the modern river, and represent drainage within the modern catchment. At higher levels there are three older terraces, the Three Pigeons, Tiddington and Chilworth terraces, which are assigned to MIS 16, 14 and 12. With much gentler downstream gradients, these are fragmentary remnants of much more substantial fluvial deposits, indicating a much larger river that was disrupted by the Anglian (MIS 12) glaciation. This interpretation supersedes an earlier view that the glacigenic deposits in the Thame headwaters correlate with the Blackditch terrace, the highest of the younger group, which has hitherto provided an argument that the glaciation in this region occurred in MIS 10. It is suggested that the headwaters of the pre-Anglian ‘Greater Thame’ river were located near Northampton and that the Milton Sands of that area represent an upstream counterpart of the Chilworth terrace deposits. It is envisaged that this early Middle Pleistocene drainage geometry, located between the Jurassic limestone and Chalk escarpments, developed as a result of the increase in uplift rates that followed the Mid-Pleistocene Revolution (MPR). It is suggested that before this time, including during the Early Pleistocene, the modern Thame catchment and adjacent regions drained southeastward through the Chalk escarpment, but these small rivers lacked the erosional power to cut through the Chalk in pace with the faster uplift occurring in the early Middle Pleistocene, and so became diverted to the southwest, subparallel to the Chalk escarpment, to form the pre-Anglian ‘Greater Thame’ tributary of the Upper Thames. The post-MPR uplift is estimated to decrease northwestward from 90 m in the Middle Thames to 75 m near the Thame-Thames confluence and to 65 m upstream of Oxford. The post-Anglian (post-450 ka) component of uplift decreases northward from 33 m near the Thame-Thames confluence to an estimated ∼20 m in the Northampton area; the relative stability of the latter area makes feasible the proposed correlation between the Milton Sands and the pre-Anglian River Thame. Limited post-Anglian uplift in the Northampton area is also inferred from the upstream convergence of the terraces of the modern rivers Nene and Great Ouse. These observed lateral variations in vertical crustal motions reflect lateral variations in crustal properties (including heat flow, crustal thickness, and thickness of underplating at the base of the crust) that are known independently. This study thus provides, for the first time, an integrated explanation of the Pleistocene drainage development across a large region of central-southern England.  相似文献   
73.
Unknowingly lumping cryptic species in biological monitoring studies hinders progress in understanding their functioning in a wide range of research fields including population dynamics, ecophysiology and community ecology. The common polychaete worm Scoloplos cf. armiger is a cryptic species complex comprising entirely different developmental modes: holobenthic and pelago-benthic development. In the northeast Atlantic, three putative species have been described on the basis of molecular data and a breeding study. We report on the development of a fast genotyping assay and on the occurrence and distribution of different molecular types in the western Wadden Sea. The genotyping assay consists of PCR-RFLP analysis by two enzymes of a mitochondrial (cox3-trnQ-nad6) DNA segment. A new, fourth type was observed and this was the only type whose geographical distribution was not uniform but instead skewed toward the eastern part of the study area. All three hitherto known types were also observed and these three displayed a significant difference in depth distribution within the study area. This is the first ecological difference reported for the ‘Subtidal Clade’ (SC) versus the ‘Type Locality Clade’ (TLC). The new type (‘Intertidal Clade 2’) had a similar distribution to what is known as the Intertidal Clade (IC). However, the most striking observation is the large degree of overlap between the depth distributions in the western Wadden Sea, where the clade names ‘Intertidal’ and ‘Subtidal’ do not necessarily reflect local species composition. The necessity to genotype Scoloplos cf. armiger in monitoring programs is emphasized.  相似文献   
74.
Infiltration sustainable drainage systems (SuDS) such as soakaways and permeable pavements use the capacity of the subsurface to attenuate surface water. The implementation of SuDS is required by the Floods and Water Management Act 2010, and the associated National Standards for Sustainable Drainage prioritise infiltration over other surface water drainage methods. This paper describes the development of a nationally derived Infiltration SuDS Map that enables preliminary assessment of the suitability of the ground for infiltration SuDS. It shows that national geological and hydrogeological datasets, developed by the British Geological Survey, can be used to support early planning decisions. The map comprises 24 GIS layers that both summarise and provide subsurface information on the suitability of the ground with respect to significant flooding and stability constraints, the drainage potential and considerations relating to ground stability and groundwater protection. The map was validated using an independent database of SuDS installations and was found to accurately describe the ground conditions in all 27 cases. The Infiltration SuDS Map suggests that 34.5 % of the United Kingdom is suitable or probably suitable for free-draining SuDS, but that the potential for infiltration SuDS at the city-scale varies depending on the ground conditions. For example, 60 % of Bradford was deemed as suitable, or probably suitable for Infiltration SuDS, whereas only 19 % of the area of Leicester was similarly classified.  相似文献   
75.
Intensive field monitoring of a reach of upland gravel‐bed river illustrates the temporal and spatial variability of in‐channel sedimentation. Over the six‐year monitoring period, the mean bed level in the channel has risen by 0·17 m with a maximum bed level rise of 0·5 m noted at one location over a five month winter period. These rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2·6 times and overbank flow time increasing by 12·8 hours. This work raises the profile of coarse sediment transfer in the design and operation of river management, specifically engineering schemes. It emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic. Exploration of the sediment supply and transfer system can explain patterns of channel sedimentation. The complex spatial, seasonal and annual variability in sediment supply and transfer raise uncertainties into the system's response to potential changes in climate and land‐use. Thus, there is a demand for schemes that monitor coarse sediment transfer and channel response. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
76.
We report on a marine electromagnetic (EM) survey across two portions of the New Jersey continental margin that have been previously shown to contain buried paleo-channels. The EM method used provides bulk porosity estimates to depths of around 20 m below the seafloor and is thus able to place porosity constraints on the nature of the channel infill and the contrast in physical properties across the channel boundaries. Our data show that a key condition for the channels to have an electrical signature is that they incise an underlying regional unconformity, R, thought to represent a subaerially eroded surface, exposed during the late Wisconsinan glaciation. Channels that cut R are seen through increases in apparent porosity. Another seismically imaged channel sequence, which lies within the outer-shelf sediment wedge sequence above R, does not have an electrical signature, indicating that the sediments above and below the channel boundaries have similar physical properties.  相似文献   
77.
78.
Glacial geomorphologic features composed of (or cut into) Llanquihue drift delineate former Andean piedmont glaciers in the region of the southern Chilean Lake District, Seno Reloncav', Golfo de Ancud, and northern Golfo Corcovado during the last glaciation. These landforms include extensive moraine belts, main and subsidiary outwash plains, kame terraces, and meltwater spillways. Numerous radiocarbon dates document Andean ice advances into the moraine belts during the last glacial maximum (LGM) at 29,363–29,385 14C yr BP , 26,797 14C yr BP , 22,295–22,570 14C yr BP , and 14,805–14,869 14C yr BP . Advances may also have culminated at close to 21,000 14C yr BP , shortly before 17,800 14C yr BP , and shortly before 15,730 14C yr BP . The maximum at 22,295–22,567 14C yr BP was probably the most extensive of the LGM in the northern part of the field area, whereas that at 14,805–14,869 14C yr BP was the most extensive in the southern part. Snowline depression during these maxima was about 1000 m. Andean piedmont glaciers did not advance into the outer Llanquihue moraine belts during the portion of middle Llanquihue time between 29,385 14C yr BP and more than 39,660 14C yr BP . In the southern part of the field area, the Golfo de Ancud lobe, as well as the Golfo Corcovado lobe, achieved a maximum at the outermost Llanquihue moraine prior to 49,892 14C yr BP . Pollen analysis of the Taiquemmire, which is located on this moraine, suggests that the old Llanquihue advance probably corresponds to the time of marine isotope stage 4. The implication is that the Andean snowline was then depressed as much as during the LGM. A Llanquihue-age glacier expansion into the outer moraine belts also occurred more than about 40,000 14C yr BP for the Lago Llanquihue piedmont glacier.  相似文献   
79.
Interhemispheric Linkage of Paleoclimate During the Last Glaciation   总被引:4,自引:0,他引:4  
Combined glacial geologic and palynologic data from the southern Lake District, Seno Reloncaví, and Isla Grande de Chiloé in middle latitudes (40°35’–42°25’S) of the Southern Hemisphere Andes suggest (1) that full-glacial or near-full-glacial climate conditions persisted from about 29,400 to 14,550 14C yr BP in late Llanquihue time, (2) that within this late Llanquihue interval mean summer temperature was depressed 6°–8°C compared to modern values during major glacier advances into the outer moraine belt at 29,400, 26,760, 22,295–22,570, and 14,550–14,805 14C yr BP , (3) that summer temperature depression was as great during early Llanquihue as during late Llanquihue time, (4) that climate deteriorated from warmer conditions during the early part to colder conditions during the later part of middle Llanquihue time, (5) that superimposed on long-term climate deterioration are Gramineae peaks on Isla Grande de Chiloé that represent cooling at 44,520–47,110 14C yr BP (T-11), 32,105–35,764 14C yr BP (T-9), 24,895–26,019 14C yr BP (T-7), 21,430–22,774 14C yr BP (T-5), and 13,040–15,200 14C yr BP (T-3), (6) that the initial phase of the glacial/interglacial transition of the last termination involved at least two major steps, one beginning at 14,600 14C yr BP and another at 12,700–13,000 14 C yr BP , and (7) that a late-glacial climate reversal of ≥2–3° C set in close to 12,200 14C yr BP , after an interval of near-interglacial warmth, and continued into Younger Dryas time. The late-glacial climate signal from the southern Chilean Lake District ties into that from proglacial Lago Mascardi in the nearby Argentine Andes, which shows rapid ice recession peaking at 12,400 14C yr BP , followed by a reversal of trend that culminated in Younger-Dryas-age glacier readvance at 11,400–10,200 14C yr BP . Many full- and late-glacial climate shifts in the southern Lake District match those from New Zealand at nearly the same Southern Hemisphere middle latitudes. At the last glacial maximum (LGM), snowline lowering relative to present-day values was nearly the same in the Southern Alps (875 m) and the Chilean Andes (1000 m). Particularly noteworthy are the new Younger-Dryas-age exposure dates of the Lake Misery moraines in Arthur's Pass in the Southern Alps. Moreover, pollen records from the Waikato lowlands on North Island show that a major vegetation shift at close to 14,700 14C yr BP marked the beginning of the last glacial/interglacial transition (Newnham et al. 1989). The synchronous and nearly uniform lowering of snowlines in Southern Hemisphere middle-latitude mountains compared with Northern Hemisphere values suggests global cooling of about the same magnitude in both hemispheres at the LGM. When compared with paleoclimate records from the North Atlantic region, the middle-latitude Southern Hemisphere terrestrial data imply interhemispheric symmetry of the structure and timing of the last glacial/interglacial transition. In both regions atmospheric warming pulses are implicated near the beginning of Oldest Dryas time (~14,600 14C yr BP) and near the Oldest Dryas/Bölling transition (~12,700–13,000 14 C yr BP ). The second of these warming pulses was coincident with resumption of North Atlantic thermohaline circulation similar to that of the modern mode, with strong formation of Lower North Atlantic Deep Water in the Nordic Seas. In both regions, the maximum Bölling-age warmth was achieved at 12,200–12,500 14 C yr BP , and was followed by a reversal in climate trend. In the North Atlantic region, and possibly in middle latitudes of the Southern Hemisphere, this reversal culminated in a Younger-Dryas-age cold pulse. Although changes in ocean circulation can redistribute heat between the hemispheres, they cannot alone account either for the synchronous planetary cooling of the LGM or for the synchronous interhemispheric warming steps of the abrupt glacial-to-interglacial transition. Instead, the dominant interhemispheric climate linkage must feature a global atmospheric signal. The most likely source of this signal is a change in the greenhouse content of the atmosphere. We speculate that the Oldest Dryas warming pulse originated from an increase in atmospheric water-vapor production by half-precession forcing in the tropics. The major thermohaline switch near the Oldest Dryas/Bölling transition then couldhave triggered another increase in tropical water-vapor production to near-interglacial values.  相似文献   
80.
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