‘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.     

Antarctic history: A reply to professor W. H. Hobbs

On July 25th 1983 a severe thunderstorm brought torrential rain and flooding to a small valley near Newcastleton in Roxburghshire. At one site within the valley, around 65 mm of rainfall was recorded in 75 minutes, though this was probably 2 km from the centre of the storm. The resulting peak flow was estimated at almost 170 m³s^‐1 from a drainage area of 36.9 km². Lightning killed some livestock whilst many more were drowned. The storm triggered peat slides on several hillsides and caused extensive erosion of river banks and damage to buildings and bridges. The associated high sediment load killed fish stocks in the receiving waters. The flood was a significant event in terms of its human disruption and its impact on the natural environment.     

A comparison between the Mediterranean climates of Eurasia and the Americas

On the 19th and 20th September 1981 heavy rain fell throughout Scotland. Almost 140mm was recorded for the 24 hours up to 9.00 am on the 20th at Dundonnell in Wester Ross, an event with a recurrence interval of approximately 120 years. The storm generated a peak discharge of c.60m³ s‐¹ on the Ardessie Burn which drains a 13.3km² catchment on the northwestern slopes of An Teallach. The resulting flood caused severe localised bank erosion and partially destroyed a fish farm. The total volume of measured flood deposits exceeded 1800 tonnes, approximately equal to 14 years normal average annual non‐dissolved sediment output. The identification of specific sediment source areas and deposition sites allows an assessment of geomorphic work in terms of direct landscape adjustment in response to extreme rainfall. The flood stresses the importance of rare events in the landscape evolution of upland environments and the influence of antecedent catchment conditions.     

敦煌莫高窟降雨分布及入渗特征研究

敦煌莫高窟文物具有唯一性和脆弱性,干燥环境是壁画和塑像长久保存的保障,降雨是病害发生诱因。为了弄清降雨对文物的损害机制,本研究通过气象监测数据分析和野外人工降雨模拟试验,分析莫高窟降雨分布特征和窟顶戈壁降雨入渗和产流规律,为开展洞窟内壁画病害发育机理分析和实施莫高窟洪水风险预控提供理论依据。25年气象监测数据分析表明,莫高窟区域多年平均降水量39mm,集中在5~8月,降雨类型主要为微雨和小雨,频现大于76%,大雨及暴雨均为突发性强降雨,频现仅为1.5%,常常伴随区域洪水的发生。降雨模拟试验结果表明,当平均降雨强度0.75mm/min,降雨历时160min时,入渗湿润锋迁移至深度80cm左右即趋于平衡。但是,高密度电阻率探测表明洞窟地层2~3m处,水分饱和度可达60%左右,极易带动可溶盐向壁画地仗层富集,致使病害发生发展。经计算,窟顶戈壁径流系数0.016,产流能力非常低。区域洪水主要来源于莫高窟周边戈壁及野马山地带降雨汇流。     

Ecohydrology and Environmental Change to Lake Albacutya and Wyperfeld Park in North‐Western Victoria,Australia

Lake Albacutya is a well‐known intermittent lake in north‐western Victoria. The lake is near the termination of the Wimmera River. From time‐to‐time the lake fills and flow passes down Outlet Creek into Wyperfeld National Park. The wetlands associated with the lake have a high biodiversity value and are named in international treaties. This paper examines the hydrologic factors associated with lake filling and flow into Wyperfeld. The lake has filled approximately six times since 1880 and has partially filled on other occasions. Examination of rainfall data from 1875 at Horsham gave no indication of long term rainfall decline, and showed that rainfall at Horsham can be viewed as representative of rainfall in the Wimmera River catchment. However a double‐mass analysis showed that the relationship between the Wimmera River flow and rainfall has varied from 1890 to the present. Examination of data associated with six fillings of Lake Albacutya suggested that filling is a two‐year event requiring at least 550 GL of flow passing Horsham over the two years immediately associated with the flood. A simple model based on rainfall and this threshold reproduced observed characteristics of the data reasonably well. This suggested that the flooding frequency of Lake Albacutya has dropped from about one in 25 years in the natural state to a substantially lower frequency under current river conditions. The results also suggested that because of changes in the Wimmera River the last filling and flood into Wyperfeld in 1976 was far smaller than it would otherwise have been. This is consistent with field mapping of the flood in relation to River Red Gum (Eucalyptus camaldulensis Dehnh.) stands. Analysis of the health of these stands showed major dieback with the severity of this being roughly proportional to the distance from the 1976 flood boundaries. An examination of values associated with the lake and adjoining Wyperfeld National Park suggested that biodiversity and economic values are and will be compromised by the reduction in flooding. In particular, an internationally‐known provenance of Red Gum is at risk, and bird‐breeding opportunities have diminished.     

Methods for assessing stormwater management at archaeological sites: Copan Ruins case study

Archaeological sites may be discovered by fortuitous soil erosion, but their protection requires deliberative stormwater management plans and estimates of runoff volumes. This paper uses the Maya site of Copan, Honduras to demonstrate widely applicable methods to estimate runoff, including use of satellite rainfall data processed by single parameter models. Our analysis compares present day estimates of runoff and erosion with those of two historic periods, 900 A.D during peak Maya occupation of the Great Plaza, and 1800 A.D. prior to excavation when the site was mostly forest covered. For each period, the watershed area, soil, land cover, and rainfall data were used with a single parameter Curve Number model to estimate the runoff volume for annual to decadal storms. The maximum runoff depth and erosive potential in conveyance channels was then computed with the HEC-RAS model. The models did not predict runoff would occur for the forested period of 1800 A.D., but predicted that runoff for 900 and post-1800 A.D was large enough to cause the erosion observed in the drainage channel today. Our results provide runoff magnitudes that demonstrate the need for Copan Maya designed stormwater removal infrastructure described in earlier archaeological analysis. The need for stormwater removal was also designed into the wet Maya site of Palenque, while stormwater capture and storage was designed into the Maya sites of Tikal, a drier site due to local drainage characteristics and water availability. Methods used in stormwater runoff analysis can empower communities and managers to develop scientifically and culturally appropriate non-structural management methods to conserve archaeological sites.     

The inclusion of sustainable drainage systems in flood management in the post‐industrial city: A case study of Glasgow

The management of urban stormwater and flooding is challenging, particularly within older, post‐industrial urban environments where infrastructure, housing and businesses already operate. The urban environment constrains opportunities for the development and integration of new approaches to drainage management, particularly the use of sustainable drainage systems (SuDS). These issues are investigated through a case study of Glasgow. The northeast of the city suffered significant urban flooding in July 2002 following an intense con‐vective summer storm. This event overloaded the urban drainage system, which was heavily integrated and led to the back flow of foul water into streets and homes. This study examines the response to this event and the construction of an integrated drainage management plan for the city, the Glasgow Strategic Drainage Plan (GSDP), which includes greater use of SuDS in tackling the city's capacity problems. Reflecting on the interdisciplinary nature of urban drainage management, this study adopts a social science method, undertaking semi‐structured interviews with key actors involved in producing the GSDP.     

Stable nitrogen isotope values in arid‐land kangaroos correlated with mean annual rainfall: potential as a palaeoclimatic indicator

Bone collagen stable nitrogen isotope values are reported for modern kangaroos (Macropus spp.) from eight field sites along a 1160 km south–north transect from temperate coastal to arid interior South Australia, in order to investigate δ¹⁵N tissue variability in relation to rainfall and relative humidity. Mean annual rainfall along the transect ranges from 775 mm at Mount Gambier in the southeastern coast to 176 mm at Innamincka in the arid northern interior, while 3pm relative humidity ranges from 73% at coastal Flinders Chase to 36% at Innamincka. In arid habitats (176–238 mm rainfall), the δ¹⁵N values of kangaroo bone collagen become more positive in relation to decreasing mean annual rainfall (r² = 0.98), while there is only a weak correlation with relative humidity (r² = 0.67). In contrast, in temperate and semi‐arid coastal habitats (350–775 mm), there is no correlation between kangaroo bone collagen δ¹⁵N values and rainfall (r² = 0.0011) or between δ¹⁵N values and relative humidity (r² = 0.0035). Thus, in South Australia, kangaroo bone collagen δ¹⁵N values do not show a simple linear correlation with either rainfall or relative humidity across all habitats. These results suggest that stable nitrogen isotope analyses of herbivore bones obtained from archaeological and palaeontological sites may provide a reliable proxy for past rainfall values in arid‐land ecosystems. Copyright © 2007 John Wiley & Sons, Ltd.     

Tropical mesoscale rainfall patterns: the opening of the monsoon in the Townsville area,December 1988

Rainfall during six days of monsoonal activity in the 1988/89 wet season is examined in terms of the influence of synoptic scale winds on mesoscale rainfall activity over the Townsville coastal plain (3450 km²). The resulting rainfall patterns. which were based on observations from a dense mesoscale network of 133 gauge points. are presented as isohyetal maps of twenty-four hour totals for each day in the study period. The study has shown that the distribution of rainfall is related to the influence of synoptic scale wind vectors, which provide upper level steering of convective activity. In addition. the interaction between local winds and synoptic circulation is deemed important for inducing convergence and precipitation. Rainfall generated is then directed by the prevailing upper synoptic flow. Orographic effects also appear to be significant, in that rainfall distribution tends to favour slopes on the windward side of the synoptic scale winds. The rainfall patterns described are probably typical of many of those that occurred throughout the 1988/89 wet season, due to the likely persistence of these mesoscale precipitation mechanisms. Similar mechanisms are also likely to occur over the study area in other wet seasons and elsewhere in the seasonally wet and dry tropics.     

Seismic Reliability of Code-Conforming Italian Buildings

ABSTRACT

This paper presents and discusses some research results related to the seismic failure risk of standard, residential and industrial, buildings designed for damage, and life-safety according to the Italian seismic code, which is somewhat similar to Eurocode 8. The five considered structural typologies are as follows: masonry, cast-in-place reinforced concrete, precast reinforced concrete, steel, and base-isolated buildings. The archetype structures have been designed according to standard practice at three sites, representative of the seismic hazard across the country. Seismic risk is defined here as the annual rate of earthquakes able to cause structural failure in terms of usability-preventing damage and global collapse. For each structure, the failure rates have been evaluated in the framework of performance-based earthquake engineering, that is, via integration of site’s probabilistic hazard and structural fragility. The former has been computed consistently with the official hazard model for Italy that is also used to define design actions in the code. The latter has been addressed via nonlinear dynamic analysis of three-dimensional numerical structural models. Results indicate that, generally, design procedures are such that seismic structural reliability tends to decrease with increasing seismic hazard of the building site, despite the homogeneous return period of exceedance of the design seismic ground-motion.     

New Evidence of the Effect of Transaction Costs on Residential Mobility*

Abstract. Transaction costs have attracted considerable attention in the theoretical literature on residential mobility. Transaction costs are thought to cause suboptimal consumption of housing but may also negatively affect labor market outcomes. In the current paper, we demonstrate empirically for the Netherlands that transaction costs have a strong negative effect on the owners' probability of moving. Under a range of different specifications, it appears that a 1 percent‐point increase in the value of transaction costs—as a percentage of the value of the residence—decreases residential mobility rates by (at least) 8 percent. The estimates imply that ownership to ownership mobility rates would be substantially higher in the absence of the current 6 percent ad valorem buyer transaction tax. Our estimates are consistent with the observation that in the Netherlands ad valorem transaction costs mainly consist of buyer transaction costs.     

Storm Drains as Assemblages: The Political Ecology of Flood Risk in Post‐Colonial Bangalore

Cities around the world are increasingly prone to unequal flood risk. In this paper, I “materialize” the political ecology of urban flood risk by casting stormwater drains—a key artifact implicated in flooding—as recombinant socionatural assemblages. I examine the production of flood risk in the city of Bangalore, India, focusing on the city's informal outskirts where wetlands and circulations of global capital intermingle. Staging a conversation between Marxian and Deleuzian positions, I argue, first, that the dialectics of “flow” and “fixity” are useful in historicizing the relational politics of storm drains from the colonial to the neoliberal era. Second, flood risk has been heightened in the contemporary moment because of an intensified alignment between the flow/fixity of capital and storm drains. Storm drains—and the larger wetlands that they traverse—possess a force‐giving materiality that fuels urban capitalism's risky “becoming‐being”. This argument raises the need for supplementing political‐economic critiques of the city with sociomaterialist understandings of capitalism and risk in the post‐colonial city. The paper concludes with reflections on how assemblage thinking opens up a more distributed notion of agency and a more relational urban political ecology.     

New Statistical Approaches to Intra‐individual Isotopic Analysis and Modelling of Birth Seasonality in Studies of Herd Animals

This paper introduces improved methods for statistically assessing birth seasonality and intra‐annual variation in δ¹⁸O from faunal tooth enamel. The first method estimates input parameters for use with a previously developed parametric approach by C. Tornero et al. The second method uses a non‐parametric clustering procedure to group individuals with similar time‐series data and estimate birth seasonality. This method was successful in analysing data from a modern sample with known season of birth, as well as two heterogeneous archaeological data sets. Modelling indicates that the non‐parametric approach estimates birth seasonality more successfully than the parametric method when less of the tooth row is preserved. The new approach offers a high level of statistical rigour and flexibility in dealing with the time‐series data produced through intra‐individual sampling in isotopic analysis.     

A Survey of Soil Erosion in Australia using Caesium‐137

A survey of soil erosion was conducted in Australia using the fallout radioisotope caesium‐137 as an indicator of topsoil redistribution. Two hundred and six sites were sampled, 100 within rotational cropping and horticultural use, 52 within uncultivated permanent pasture and forest, and 54 in rangelands. Average net soil losses were approximately equal for cultivated cropping lands and rangelands (ca. 5.5 t ha^?1 yr^?1), and just over 1 t ha^?1 yr^?1 for pasture and forest. The Mann Whitney U Test revealed that losses under cropping and rangeland conditions were significantly higher (p < 0.05) than under uncultivated pasture and forest. Soil loss was negatively correlated with mean annual rainfall and slope gradient, and positively correlated with slope length (Spearman's rank correlation). There was no correlation between rates of soil loss and a rainfall erosi‐vity index. An assessment of erosional events was provided by landholders for 104 sites, with their ranking being weakly but significantly correlated with soil loss estimates (r =+0.35). Sixty percent of sites had net soil losses greater than 1 t ha^?1 yr^?1, and 74% of sites had losses of more than 0.5 t ha^?1 yr^?1. This latter rate may be regarded as a limit for a tolerable level of soil loss. These high rates of soil loss have occurred since the mid‐1950s despite there being significant landholder awareness of the soil erosion hazard.     

Three‐Dimensional Neurointerpolation of Annual Mean Precipitation and Temperature Surfaces for China

Climatic variables such as annual mean precipitation and temperature display complex and nonlinear variation with latitude, longitude, and elevation. Neural networks are universal approximators and very good at detecting and representing nonlinear relationships between dependent and independent variables. In this paper we use resilient backpropagation (Rprop) neural networks to interpolate annual mean precipitation and temperature surfaces for China. Climate surfaces are interpolated from a total of 288 long‐term climate station data points using latitude, longitude, and elevation derived from a 5‐kilometer resolution digital elevation model. Initial trials of Rprop suggested very fast learning, insensitivity to selection of learning parameters, and a tendency not to overtrain. Cross‐validation was used to determine the best network structure and assess the error inherent in climate interpolation. With the error explicit, the final neurointerpolations of annual mean precipitation and temperature were constructed using all 288 climate station data points. Maps of residuals are also presented. The neurointerpolation of temperature was very successful and captures most of the regional trends found in established climate maps of China as well as significant topographically defined detail. For annual mean temperature the Rprop neural network was found to be an accurate and robust global spatial interpolator. However, the precipitation surface captures only the major latitudinally and continentally defined trends and misses many subregional rainfall features probably because of the influence of other nonparameterized atmospheric and topographic factors.     

IMMIGRATION AND HOUSING BOOMS: EVIDENCE FROM SPAIN*

ABSTRACT We provide causal estimates of the effect of immigration on house prices and construction activity in Spain over the period 2000–2010. During this period Spain experienced spectacular swings in both immigration and the housing market. Our instrumental‐variables estimates suggest that between 2000 and 2010, immigration led to an average 1.5 percent annual increase in the working‐age population. This was responsible for an annual increase in housing prices of about 2 percent, and for a 1.2–1.5 percent increase in housing units. Overall, immigration was responsible for one quarter of the increase in prices and about half of the construction activity over the decade.     

The atlas of Africa: The persistence of European perspectives

Régine Van Chi‐Bonnardel. The Atlas of Africa. Prepared by Jeune Afrique. New York: The Free Press, 1974. 335 pp. Maps, bargraph diagrams, index‐gazetteer, and glossary. $80.00.     

Can South–South Cooperation Compete? The Development Bank of Latin America and the Islamic Development Bank

Southern‐led multilateral development banks (MDBs) play a key role in harnessing global capital to finance the sectors most important to borrowers, especially infrastructure. Two prominent Southern MDBs, the Development Bank of Latin America (CAF) and the Islamic Development Bank (IsDB), have become crucial drivers of regional infrastructure growth. This article explores whether their performance has lived up to their goals of establishing borrower control over bank governance without sacrificing financial dynamism. Using power‐weighted voting indices for member representation on bank boards, the authors determine that these banks offer borrowers much more representation on their boards than do their Northern‐based counterparts, the Inter‐American Development Bank (IDB) and the World Bank International Bank for Reconstruction and Development (IBRD). The article also analyses bank operations to determine whether their governance structure impacts their internal performance, as reflected on balance sheets, and external performance — gaining relevance in development finance and particularly in infrastructure lending, including the burgeoning sector of sustainable (climate‐resilient) infrastructure. The authors find that the CAF and IsDB have become major players in development finance, including in sustainable infrastructure. However, important issues remain in relation to their continued internal capacity development, especially with regard to the environmental and social safeguards necessary to oversee lending.     

OBTAINING PROBABILISTIC ESTIMATES OF DISPLACEMENT ON A LANDSLIDE DURING FUTURE EARTHQUAKES

The assessment of earthquake triggered landslide hazard may be undertaken using both deterministic and probabilistic techniques. Probabilistic methods have been developed because much of the data can be considered as random variables where parameters such as the angle of internal friction and moisture content do not have a single fixed value but may assume any number of values across a range. This random variability can be modelled by a probability density function (PDF) which describes the relative likeli-hood that a random variable will assume a particular value. Instead of using just the average or expected value of an input parameter, the complete range of possible values can be used to estimate a range of possible outcomes. Thus the probability of a slope being unstable can be obtained rather than a single indicator of stability. Such proba-bilistic analyses allow for the incorporation of the likely variability of each parameter and therefore allow a more intimate assessment of slope stability to be derived. Utilising empirical relationships for calculating earthquake ground motions and associated slope displacement, an investigation was undertaken to identify the contribution that modern simulation techniques could make to the assessment of earthquake-triggered landslides. To achieve this, geotechnical and earthquake data obtained from a deep-seated landslide triggered during the M _w 7.0 Loma Prieta earthquake was used. By incorporating the variability of the geotechnical parameters and the uncertainty in earthquake location the model derived the probabilities associated with increasing amounts of slope displacement during future probable earthquakes. Analysis was undertaken for four of the principal fault segments in the San Francisco Bay area. These estimates were then combined with the occurrence probabilities of the earthquakes to provide temporal estimates of dis-placement for a 30 year period. Results indicated that a M _w 7.0 earthquake located on the Peninsula Segment of the San Andreas fault was most hazardous with a 11% chance of minor slope displacement (≥0.10 m) and a 6% chance of moderate slope displacement (≥0.30 m) within the next 30 years.