A spatio-temporal analysis of fires in the Southern African Development Community region     

S. Strydom  M. J. Savage 《Natural Hazards》2018,92(3):1617-1632

Wildfires are considered one of the most common disasters in southern Africa resulting in a high number of human fatalities and financial loss on an annual basis. It is believed that increased population growth, as well as more concentrated settlement planning, is likely to result in increased fire disasters and increased human fatalities as a direct result of wildfires. To better understand the spatial and temporal variations and characteristics of wildfires in the Southern African Development Community (SADC), an 11-year dataset of satellite-derived Active Fire Hotspots was analysed using an open source geographic information system. Results indicate that annual fire frequency for most SADC countries is highly variable. Increasing trends in annual fire frequency were observed in five out of 13 SADC countries with a decrease in annual fire frequency observed in four countries. An additional four countries displayed a somewhat stable trend in fire frequency. Temporally, fires have been observed in all months for the SADC region although distinct fire seasons were observed, largely driven by uni-modal rainfall seasons. The timing, location and strength of rainfall seasons have a marked influence on fire activity depending on the seasonal wet and dry (growing and desiccation) periods. Fire activity in vegetation eco-regions can be attributed to both natural and anthropogenic sources of ignition. However, increased anthropogenic agroforestry activities have resulted in increased fire activity in numerous SADC eco-regions with woodlands, savannahs and montane grassland eco-regions being most prone to wildfires.  相似文献   

Crust and mantle thickening beneath the southern portion of the Southern Alps, New Zealand     

S. Bourguignon  T. A. Stern  M. K. Savage 《Geophysical Journal International》2007,168(2):681-690

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Groundwater as a sustainable source of income and wealth creation     

Richard Martin  Richard Savage  Richard Pyvis 《Environmental Earth Sciences》2013,70(5):1965-1969

Asia, and in particular the Mekong Delta region, is under increasing water use pressure. Food production and quality is one element of these growing pressures, as is water management. The authors have first-hand knowledge and experience in groundwater use and management in rural Thailand. Through the adoption of a micro-management, demand-driven approach, with its ultimate objective of sustainability and the betterment of the quality of human life, the Mekong delta and other similar rural areas in Asia offer considerable opportunity for more optimal sustainable exploitation of groundwater. This water source should be prioritized for village usage, which if properly allocated and managed, will lift a significant human population from poverty, into a more sustainable existence. This readily available, reliable groundwater resource exists and has both the capacity for abundant storage as well as the potential for commercial and household supply. The focus has been on understanding the distribution of the delta’s relatively shallow, well sustained, and consistently recharged groundwater resource, and its potential symbiotic linkage to low-volume household demand. Water has been employed in a variety of ways from improving quality of life and sanitation to generating income through the cultivation of cash crops and other similar productive uses. The fundamental aims of the initial model and subsequent trials have been to harness this robust water source and deliver otherwise unattainable income to households. As the following, more detailed study of rural Thailand demonstrates, the benefits of such an approach deliver sustainable enhancements to the quality of constituents’ lives, are environmentally sensitive and sustainable, and harmonize with governmental efforts to alleviate poverty through the enablement of income generation from groundwater utilization.  相似文献   

Latitudinal and altitudinal controls of Titan’s dune field morphometry     

A. Le Gall  A.G. Hayes  R. Ewing  M.A. Janssen  J. Radebaugh  C. Savage  P. Encrenaz 《Icarus》2012,217(1):231-242

Dune fields dominate ～13% of Titan’s surface and represent an important sink of carbon in the methane cycle. Herein, we discuss correlations in dune morphometry with altitude and latitude. These correlations, which have important implications in terms of geological processes and climate on Titan, are investigated through the microwave electromagnetic signatures of dune fields using Cassini radar and radiometry observations. The backscatter and emissivity from Titan’s dune terrains are primarily controlled by the amount of interdune area within the radar footprint and are also expected to vary with the degree of the interdunal sand cover. Using SAR-derived topography, we find that Titan’s main dune fields (Shangri-La, Fensal, Belet and Aztlan) tend to occupy the lowest elevation areas in Equatorial regions occurring at mean elevations between ～?400 and ～0 m (relative to the geoid). In elevated dune terrains, we show a definite trend towards a smaller dune to interdune ratio and possibly a thinner sand cover in the interdune areas. A similar correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. The altitudinal trend among Titan’s sand seas is consistent with the idea that sediment source zones most probably occur in lowlands, which would reduce the sand supply toward elevated regions. The latitudinal preference could result from a gradual increase in dampness with latitude due to the asymmetric seasonal forcing associated with Titan’s current orbital configuration unless it is indicative of a latitudinal preference in the sand source distribution or wind transport capacity.  相似文献   

Homogeneous distribution of Fe isotopes in the early solar nebula     

Kun Wang  Frédéric Moynier  Jean‐Alix Barrat  Brigitte Zanda  Randal C. Paniello  Paul S. Savage 《Meteoritics & planetary science》2013,48(3):354-364

To examine the iron (Fe) isotopic heterogeneities of CI and ordinary chondrites, we have analyzed several large chips (approximately 1 g) from three CI chondrites and three ordinary chondrites (LL5, L5, and H5). The Fe isotope compositions of five different samples of Orgueil, one from Ivuna and one from Alais (CI chondrites), are highly homogeneous. This new dataset provides a δ⁵⁶Fe average of 0.02 ± 0.04‰ (2SE, n = 7), which represents the best available value for the Fe isotopic composition of CI chondrites and probably the best estimate of the bulk solar system. We conclude that the homogeneity of CI chondrites reflects the initial Fe isotopic homogeneity of the well‐mixed solar nebula. In contrast, larger (up to 0.26‰ in δ⁵⁶Fe) isotopic variations have been found between separate approximately 1 g pieces of the same ordinary chondrite sample. The Fe isotope heterogeneities in ordinary chondrites appear to be controlled by the abundances of chondritic components, specifically chondrules, whose Fe isotope compositions have been fractionated by evaporation and recondensation during multiple heating events.  相似文献   

Regional landslide-hazard assessment for Seattle, Washington, USA   总被引：13，自引：6，他引：13  

Rex L. Baum  Jeffery A. Coe  Jonathan W. Godt  Edwin L. Harp  Mark E. Reid  William Z. Savage  William H. Schulz  Dianne L. Brien  Alan F. Chleborad  Jonathan P. McKenna  John A. Michael 《Landslides》2005,2(4):266-279

Landslides are a widespread, frequent, and costly hazard in Seattle and the Puget Sound area of Washington State, USA. Shallow earth slides triggered by heavy rainfall are the most common type of landslide in the area; many transform into debris flows and cause significant property damage or disrupt transportation. Large rotational and translational slides, though less common, also cause serious property damage. The hundreds of landslides that occurred during the winters of 1995–96 and 1996–97 stimulated renewed interest by Puget Sound communities in identifying landslide-prone areas and taking actions to reduce future landslide losses. Informal partnerships between the U.S. Geological Survey (USGS), the City of Seattle, and private consultants are focusing on the problem of identifying and mapping areas of landslide hazard as well as characterizing temporal aspects of the hazard. We have developed GIS-based methods to map the probability of landslide occurrence as well as empirical rainfall thresholds and physically based methods to forecast times of landslide occurrence. Our methods for mapping landslide hazard zones began with field studies and physically based models to assess relative slope stability, including the effects of material properties, seasonal groundwater levels, and rainfall infiltration. We have analyzed the correlation between historic landslide occurrence and relative slope stability to map the degree of landslide hazard. The City of Seattle is using results of the USGS studies in storm preparedness planning for emergency access and response, planning for development or redevelopment of hillsides, and municipal facility planning and prioritization. Methods we have developed could be applied elsewhere to suit local needs and available data.  相似文献   

Changing Geographies and the Geography of Change: Some Reflections     

Victor R. Savage 《Singapore journal of tropical geography》2003,24(1):61-85

To celebrate the 50th anniversary of the Singapore Journal of Tropical Geography and the 75th anniversary of the teaching of geography in the Department of Geography, National University of Singapore, the home of the Journal, this article, based on personal reflections and "objective" academic materials, provides an overview of developments in geography in the Department and Journal. The paper argues that the department's and Journal's"identities", since the post-World War II period, have been shaped by Singapore's changing domestic politics, the changing university academic environment, the personalities and academic interests of heads of the department and the Journa's editors, the state of the changing regional and global political economic environment, and the individual research interests of faculty in the department, and reflects a complex mix of colonial/post-colonial, modern/post-modern, North-South and East-West discourses. While a defined Singapore school of geography has yet to emerge, the article shows that both the department and the Journal have made major strides in meeting the challenges of globalisation and, in the process, have gained international visibility and academic legitimacy. In particular, the Journal has consolidated its position as a major voice for academics in lesser developed countries, its platform for "tropical world" discourse and maintaining its edge in the colonial/post-colonial and modern/post-modern discourses of states within the tropics.  相似文献   

Artemia parthenogenetica in Lake Hayward, Western Australia. I. Interrupted recruitment into adult stages in response to seasonal limnology     

Alan Savage  Brenton Knott 《International Journal of Salt Lake Research》1998,7(1):1-12

Lake Hayward, Western Australia, is a pristine, monomictic coastal lake with a residual brine (depth=1.5 m) of 200 gL⁻¹: stratification in winter (May to October) followed the input of ground water and rain. The epilimnion had temperature ranges of 10–30°C, and salinity from 65–110 g L⁻¹. Maximum depth in winter was 2.4 m. The population structure of the brine shrimpArtemia parthenogenetica, the dominant metazoan grazer in Lake Hayward, was studied from September, 1989, to February, 1991. The L. Hayward population ofA. parthenogenetica is predominantly ovoviviparous with little recruitment into the adult population. Cyst production occurs in summer, and there was evidence for recruitment from cyst hatching in the winters of 1989 and 1990. Nauplii were continuously present throughout the study period. Nevertheless, recruitment through to adult stages as defined by the presence of gravid females occurred only twice: in October–December, 1989 and in December, 1990. Based on limited observations of long-term survival of laboratory cultures, we believe that the major mechanism controlling nauplius survival and recruitment ofArtemia in Lake Hayward is food quality and quantity.  相似文献   

Modeling landslide recurrence in Seattle, Washington, USA   总被引：5，自引：0，他引：5  

Diana Salciarini  Jonathan W. Godt  William Z. Savage  Rex L. Baum  Pietro Conversini   《Engineering Geology》2008,102(3-4):227

To manage the hazard associated with shallow landslides, decision makers need an understanding of where and when landslides may occur. A variety of approaches have been used to estimate the hazard from shallow, rainfall-triggered landslides, such as empirical rainfall threshold methods or probabilistic methods based on historical records. The wide availability of Geographic Information Systems (GIS) and digital topographic data has led to the development of analytic methods for landslide hazard estimation that couple steady-state hydrological models with slope stability calculations. Because these methods typically neglect the transient effects of infiltration on slope stability, results cannot be linked with historical or forecasted rainfall sequences. Estimates of the frequency of conditions likely to cause landslides are critical for quantitative risk and hazard assessments. We present results to demonstrate how a transient infiltration model coupled with an infinite slope stability calculation may be used to assess shallow landslide frequency in the City of Seattle, Washington, USA. A module called CRF (Critical RainFall) for estimating deterministic rainfall thresholds has been integrated in the TRIGRS (Transient Rainfall Infiltration and Grid-based Slope-Stability) model that combines a transient, one-dimensional analytic solution for pore-pressure response to rainfall infiltration with an infinite slope stability calculation. Input data for the extended model include topographic slope, colluvial thickness, initial water-table depth, material properties, and rainfall durations. This approach is combined with a statistical treatment of rainfall using a GEV (General Extreme Value) probabilistic distribution to produce maps showing the shallow landslide recurrence induced, on a spatially distributed basis, as a function of rainfall duration and hillslope characteristics.  相似文献   

Hydrothermal alteration of granite by meteoric fluid: an example from the Carnmenellis Granite,United Kingdom   总被引：1，自引：0，他引：1  

David Savage  Mark R. Cave  Antoni E. Milodowski  Ian George 《Contributions to Mineralogy and Petrology》1987,96(3):391-405

The interaction of granitic rock with meteoric fluid is instrumental in determining the chemistry of pore fluids and alteration mineralogy in downflow portions of convective groundwater circulation cells associated with many hydrothermal systems in the continental crust. Hydrothermal experiments and a detailed mineralogical study have been carried out to investigate the hydrothermal alteration of the Carnmenellis Granite, Cornwall, UK. Samples of drill chippings from a borehole 2 km deep in the Carnmenellis Granite have been reacted with a dilute Na-HCO₃-Cl fluid in hydrothermal solution equipment at temperatures of 80°, 150° and 250° C and a pressure of 50 MPa, with a water/rock mass ratio of 10, for experiment durations up to 200 days. Fluid samples were analysed for seventeen different chemical components, and solids were examined prior to, and after reaction using SEM, electron microprobe and conventional light optic techniques. Experimental fluids were mildly alkaline (pH 7–8.5) and of low salinity (TDS <800 mgl^–1). Mineral-fluid reaction was dominated by the dissolution of plagioclase and the growth of smectite, calcite (at all temperatures), laumontite (at 150° C), wairakite and anhydrite (at 250° C). Final fluids were saturated with respect to quartz and fluorite. Certain trace elements (Li, B, Sr) were either incorporated into solids precipitated during the experiments or sorbed onto mineral surfaces and cannot be considered as conservative (partitioned into the fluid phase) elements. Concentrations of all analysed chemical components showed net increases during the experiments except for Ca (at 250° C) and Mg (at all temperatures). A comparison of the alteration mineralogy observed in the experiments with that present as natural fracture infills in drillcore from the Carnmenellis Granite reveals that the solid products from the experiments correspond closely to mineral assemblages identified as occurring during the later stages of hydrothermal circulation associated with the emplacement of the granite.  相似文献