The Archaeology of El Niño Events and Other “Natural” Disasters

Archaeological research on disasters has increased substantially since Sheets's 1980 review of the topic, and with heightened media coverage and funding for the study of such events, archaeological interest will continue to grow. This paper examines how prehistorians have incorporated disasters into their research since 1980, using the literature on El Niño as an illustrative case, and assesses this work in relation to geographical approaches to disaster as well as concepts that have been developed within the new ecologies.     

Pressurised pastoralism in South Gobi, Mongolia: what is the role of drought?

The desert-steppe region of southern Mongolia is susceptible to drought and extreme winter weather ( dzud ) that in combination form Mongolia's worst natural hazard. Low precipitation and high climatic variability in this dryland environment impact the landscape and affect pastoralism, the dominant rural lifestyle. Using the Standardised Precipitation Index (SPI), this paper identifies drought occurrence in South Gobi Province, Mongolia. It then examines the relationship of drought with climate factors, interaction with vegetation (derived from Normalised Difference Vegetation Index - NDVI - data), and local human and livestock populations, and the dzuds of 1999–2001. Results show that drought is recurrent in the region, reaching extreme intensity most recently in 2005–2006. In contrast with the prevailing concept of drought impacting dzuds , the study did not find a connection between drought and dzud in South Gobi Province. Though repeated events, these natural hazards occur independently in the region. Climatic variables show increasing temperatures (>1°C), fluctuating precipitation patterns and a decline in vegetation cover. The principal long-term correlation of drought is with human population rather than natural factors, dzud or livestock numbers.     

REAL-TIME RISK ANALYSIS FOR HYBRID EARTHQUAKE EARLY WARNING SYSTEMS

Earthquake Early Warning Systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in reducing vulnerability and/or exposition of buildings and lifelines. In fact, recently seismologists developed efficient methods for rapid estimation of event features by means of limited information of the P-waves. Then, when an event is occurring, probabilistic distributions of magnitude and source-to-site distance are available and the prediction of the ground motion at the site, conditioned to the seismic network measures, may be performed in analogy with the Probabilistic Seismic Hazard Analysis (PSHA). Consequently the structural performance may be obtained by the Probabilistic Seismic Demand Analysis (PSDA), and used for real-time risk management purposes. However, such prediction is performed in very uncertain conditions which have to be taken into proper account to limit false and missed alarms. In the present study, real-time risk analysis for early warning purposes is discussed. The magnitude estimation is performed via the Bayesian approach, while the earthquake localization is based on the Voronoi cells. To test the procedure it was applied, by simulation, to the EEWS under development in the Campanian region (southern Italy). The results lead to the conclusion that the PSHA, conditioned to the EEWS, correctly predicts the hazard at the site and that the false/missed alarm probabilities may be controlled by set up of an appropriate decisional rule and alarm threshold.     

Forest as hazard,forest as victim: Community perspectives and disaster mitigation in the aftermath of Kelowna's 2003 wildfires

Situated within the political ecology of hazard, this article is an extended case study of the devastating 2003 wildfires in and around Kelowna, British Columbia (also known as the Okanagan Mountain Park Fire). This article reveals how compliance (or lack thereof) with fire mitigation strategies recommended by provincial, regional, and municipal agencies is complicated by differing social constructions of what constitutes ecologically sustainable forest management and community safety. Three perspectives emerge regarding the urban forests: “nature as hazard”—a volatile force to be controlled; “nature as instrumentally valuable”—a contribution to the character of one's surroundings and subsequent sense of place; and “nature as intrinsically valuable”—a distinct entity to be preserved and protected for its own sake. The article also examines how experiences of disaster influence community perceptions and result in a greater willingness to engage in fire mitigation strategies due to perceptions of heightened vulnerability. Forestry and fire mitigation agencies need to determine multiple courses of action among the varied and valid range of residents’ nature perspectives. The role of human agency in disaster mitigation must be examined, particularly as the risk of fire at the wildland‐urban interface continues to be exacerbated by encroaching human settlements and climate change.     

Managing global heritage in the face of future climate change: the importance of understanding geological and geomorphological processes and hazards

It is now widely acknowledged that human adaptation of the planet is causing significant changes to the global climate, which are being felt currently and are likely to increase in the future. This is beginning to place exceptional strains on the historic environment, here defined as both above and below ground archaeological remains. Using examples from the cultural list of World Heritage Sites in mainland Britain, this paper explores how knowledge of past and contemporary geological and geomorphological processes can provide an understanding of natural hazards and risk assessment. This, in turn, can inform management strategies to allow the protection and stabilisation of sites, limit further degradation and ensure long-term sustainability. From the analysis of published documentation available from UNESCO, it appears that natural processes have not always received the attention they deserve, and in some cases appear to have been ignored. Given the complexity of future climate change and the role that natural processes will play in determining the vulnerability of individual heritage assets, it is essential that geoscientists, archaeologists and cultural heritage managers work together to develop appropriate strategies to mitigate the effects of change in the future, especially since many of the themes developed in this paper have generic applicability across a range of landscape environments.     

TUNING OF SEISMIC HAZARD ESTIMATES BY MEANS OF OBSERVED SITE INTENSITIES

Probabilistic seismic hazard is usually assessed by means of computer codes using seis-mogenic sources, parametric catalogues, seismicity rates and attenuation relationships. All these ingredients are conditioned by expert judgement that influences the final results. Even the attenuation relationships, though strictly based on experimental data, are considered a weak point due to the difficulty of modelling the interaction between seismic energy radiation and site response, and because earthquakes do not usually repeat themselves according to one theoretical model. Recently, methods making wide use of site intensity data have been developed in regions such as Italy, where the observed seismic history at selected sites is quite exhaustive. We analyzed these observations to assess seismic hazard at about 600 sites. We used a probabilistic counting technique, integrating the observations (when necessary), with computed shakings obtained from a logistic-type attenuation model. The results were then compared with the estimates provided by the recent seismic hazard map of Italy, compiled according to the traditional probabilistic seismic hazard approach. The match shows significant differences for some sites. A tentative explanation which seems to point to three alternatives is provided: (1) The mismatch between the two methodologies might appear because the stationary assumption has a poor fit with reality (at least in certain areas); (2) Some sites show a response that is systematically different from the average values predicted using attenuation relationships; (3) The definition of seismogenic zones leads to a bias in the seismicity rate estimate.     

‘Torrents of Terror’: the August 1998 Storm and the Magnitude,Frequency and Impact of Major Floods in the Illawarra Region of New South Wales

The Illawarra Region some 80 kilometres south of Sydney is characterised by a prominent coastal escarpment that rises to 700 m within 12 km of the coast and forms a locus for frequent, high intensity rainfall events. One of the most recent recorded events occurred on 17 August 1998 with rainfall intensities at several pluviometers exceeding 120 mm hr^‐1 over a duration of one hour, with up to 249 mm falling in 3.5 hours during the main storm burst. Detailed pluviometer data indicate that the storm was non‐stationary and moved down catchment producing a widespread zone of 120 mm hr^‐1 intensity rainfall over a 30 minute duration across mid‐lower catchment areas after similar intensity but longer duration rainfall in catchment headwaters. Slope‐area reconstructions of peak discharge indicate that small catchments on the escarpment within the zone of maximum intensity experienced close to 100% rainfall‐runoff relationships, with peak discharges correlated to short duration (<1 hr) peak rainfall intensities. Widespread erosion occurred particularly where urban development had encroached on natural water courses. Debris/hyperconcentrated flows originating from both anthropogenic and natural sediment sources caused damage to urban areas. This paper provides an overview of the spatial and temporal characteristics of the 17 August 1998 storm, the hydrologic and geomorphic response of the streams, and the nature of damage to urban areas. It reassesses the frequency of recent high‐magnitude rainfall/flood events in the region, discussing the relationships between rainfall intensities, estimates of flood magnitudes and stormwater channel capacities.     

Communities and archaeology under the Soufrière Hills Volcano on Montserrat,West Indies

Abstract

The volcanically devastated landscape of Montserrat and its social fabric comprise what Maria calls a “traumascape”—a site of tragedy and catastrophe that is also a place of coping and resilience. How Montserratians engage with trauma is evident in how they remember their recent and historical pasts, and in how they are reinventing aspects of their heritage in order to sustain a distinctly Montserratian identity for the future. Such a process of coping presents challenges for conducting archaeology in collaboration with the community. In this article, we describe the experiences of a recently established project on the island (Survey and Landscape Archaeology on Montserrat) and discuss the potential for, and the obstacles involved in, developing longer-term, sustainable forms of collaboration between archaeologists and local Montserratian communities when facing the unusual circumstances of volcanic disaster and hazard.     

ON THE ROLE OF ROAD NETWORKS IN REDUCING HUMAN LOSSES AFTER EARTHQUAKES

A road-network reliability analysis for a scenario seismic event is performed for a region of southern Italy characterised by a large number of small to medium municipalities quite close to each other and served by a dense network of roads. Among the many functions of the road network, whose links may fail after an earthquake due to the collapse of the bridges within them, the one selected for the present study is that of allowing rescue operations to be carried out at the sites of collapsed schools. For this to be possible, connection must be maintained between schools that survived, rescue centres and hospitals. Required elements for the study are the fragility curves of the bridges, the schools, the hospitals and the rescue centres. Output of the study is the expected value of the fraction of the total population in the area that is in need of assistance and cannot be hospitalised due to either failure of the network or other vulnerable components.     

SEISMIC WAVE ATTENUATION FOR VRANCEA EVENTS REVISITED

New aspects of the frequency-dependent attenuation of the seismic waves travelling from Vrancea subcrustal sources toward NW (Transylvanian Basin) and SE (Romanian Plain) are evidenced by the recent experimental data made available by the CALIXTO'99 tomography experiment. The observations validate the previous theoretical computations performed for the assessment, by means of a deterministic approach, of the seismic hazard in Romania. They reveal an essential aspect of the seismic ground motion attenuation that has important implications on the probabilistic assessment of seismic hazard from Vrancea intermediate-depth earthquakes. The attenuation toward NW is shown to be a much stronger frequency-dependent effect than the attenuation toward SE and the seismic hazard computed by the deterministic approach fits satisfactorily well the observed ground motion distribution in the low-frequency band (<1Hz). The apparent contradiction with the historically-based intensity maps arises mainly from a systematic difference in the eigenperiods (type and size) of the buildings in the intra- and extra-Carpathians regions, thus the existing macroseismic data, based on buildings of small dimensions, i.e. with high eigenfrequency (5–10 Hz), can hardly be representative of the real hazard for new and large dimension, tall buildings, with eigenfrequency above 1 Hz.