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Urbanized Areas (urbanized + area)
Selected AbstractsExpected loss-based alarm threshold set for earthquake early warning systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2007Iunio Iervolino Abstract Earthquake early warning systems (EEWS) seem to have potential as tools for real-time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real-time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real-time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P -waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance-based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non-structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm-issuance and non-issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd. [source] Anthropogenic impacts upon plant species richness and net primary productivity in CaliforniaECOLOGY LETTERS, Issue 2 2005John W. Williams Abstract We assess the importance of anthropogenic land-use, altered productivity, and species invasions for observed productivity,richness relationships in California. To this end, we model net primary productivity (NPP) c. 1750 AD and at present (1982,1999) and map native and exotic vascular plant richness for 230 subecoregions. NPP has increased up to 105% in semi-arid areas and decreased up to 48% in coastal urbanized areas. Exotic invasions have increased local species diversity up to 15%. Human activities have reinforced historical gradients in species richness but reduced the spatial heterogeneity of NPP. Structural equation modelling suggests that, prior to European settlement, NPP and richness were primarily controlled by precipitation and other abiotic variables, with NPP mediating richness. Abiotic variables remain the strongest predictors of present NPP and richness, but intermodel comparisons indicate a significant anthropogenic impact upon statewide distributions of NPP and richness. Exotic and native species each positively correlate to NPP after controlling for other variables, which may help explain recent reports of positively associated native and exotic richness. [source] Using an airgun array in a land reservoir as the seismic source for seismotectonic studies in northern China: experiments and preliminary resultsGEOPHYSICAL PROSPECTING, Issue 4 2008Yong Chen ABSTRACT This paper reports the field setup and preliminary results of experiments utilizing an airgun array in a reservoir in north China for a seismotectonic study. Commonly used in offshore petroleum resource exploration, the airgun source was found to be more useful than a traditional explosive source for large-scale and long offset land seismic surveys. The airgun array, formed by four 1,500 in3 airguns (a total of 6,000 in3 in volume) was placed at a depth of 6,9 m into the reservoir to generate the pressure impulse. No direct evidence was found that the airgun source adversely affected the fish in the reservoir. The peak ground acceleration recorded on the top of the reservoir dam 100 m away was 17.8 gal in the horizontal direction; this is much less than the designed earthquake-resistance threshold of 125 gal for this dam. The energy for one shot of this airgun array is about 6.68 MJ, equivalent to firing a 1.7 kg explosive. The seismic waves generated by the airgun source were recorded by receivers of the regional seismic networks and a temporary wide-angle reflection and refraction profile formed by 100 short-period seismometers with the maximum source-receiver offset of 206 km. The seismic wave signature at these long-offset stations is equivalent to that generated by a traditional blast source in a borehole with a 1,000,2,000 kg explosive. Preliminary results showed clear seismic phases from refractions from the multi-layer crustal structures in the north China region. Forward modelling using numerical simulation confirms that the seismic arrivals are indeed from lower crustal interfaces. The airgun source is efficient, economical, environmentally friendly and suitable for being used in urbanized areas. It has many advantages over an explosive source for seismotectonic studies such as the high repeatability that is supreme for stacking to improve signal qualities. The disadvantage is that the source is limited to existing lakes or reservoirs, which may restrict experimental geometry. [source] Power function decay of hydraulic conductivity for a TOPMODEL-based infiltration routineHYDROLOGICAL PROCESSES, Issue 18 2006Jun Wang Abstract TOPMODEL rainfall-runoff hydrologic concepts are based on soil saturation processes, where soil controls on hydrograph recession have been represented by linear, exponential, and power function decay with soil depth. Although these decay formulations have been incorporated into baseflow decay and topographic index computations, only the linear and exponential forms have been incorporated into infiltration subroutines. This study develops a power function formulation of the Green and Ampt infiltration equation for the case where the power n = 1 and 2. This new function was created to represent field measurements in the New York City, USA, Ward Pound Ridge drinking water supply area, and provide support for similar sites reported by other researchers. Derivation of the power-function-based Green and Ampt model begins with the Green and Ampt formulation used by Beven in deriving an exponential decay model. Differences between the linear, exponential, and power function infiltration scenarios are sensitive to the relative difference between rainfall rates and hydraulic conductivity. Using a low-frequency 30 min design storm with 4·8 cm h,1 rain, the n = 2 power function formulation allows for a faster decay of infiltration and more rapid generation of runoff. Infiltration excess runoff is rare in most forested watersheds, and advantages of the power function infiltration routine may primarily include replication of field-observed processes in urbanized areas and numerical consistency with power function decay of baseflow and topographic index distributions. Equation development is presented within a TOPMODEL-based Ward Pound Ridge rainfall-runoff simulation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Flux and source term discretization in two-dimensional shallow water models with porosity on unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2006Vincent Guinot Abstract Two-dimensional shallow water models with porosity appear as an interesting path for the large-scale modelling of floodplains with urbanized areas. The porosity accounts for the reduction in storage and in the exchange sections due to the presence of buildings and other structures in the floodplain. The introduction of a porosity into the two-dimensional shallow water equations leads to modified expressions for the fluxes and source terms. An extra source term appears in the momentum equation. This paper presents a discretization of the modified fluxes using a modified HLL Riemann solver on unstructured grids. The source term arising from the gradients in the topography and in the porosity is treated in an upwind fashion so as to enhance the stability of the solution. The Riemann solver is tested against new analytical solutions with variable porosity. A new formulation is proposed for the macroscopic head loss in urban areas. An application example is presented, where the large scale model with porosity is compared to a refined flow model containing obstacles that represent a schematic urban area. The quality of the results illustrates the potential usefulness of porosity-based shallow water models for large scale floodplain simulations. Copyright © 2005 John Wiley & Sons, Ltd. [source] ASSESSING LAND USE IMPACTS ON WATER QUALITY USING MICROBIAL SOURCE TRACKING,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Sharon C. Long ABSTRACT: A renewed emphasis on source water protection and watershed management has resulted from recent amendments and initiatives under the Safe Drinking Water Act and the Clean Water Act. Knowledge of the impact of land use choices on source water quality is critical for efforts to properly manage activities within a watershed. This study evaluated qualitative relationships between land use and source water quality and the quantitative impact of season and rainfall events on water quality parameters. High levels of specific conductance tended to be associated with dense residential development, while organic carbon was elevated at several forested sites. Turbidity was generally higher in more urbanized areas. Source tracking indicators were detected in samples where land use types would predict their presence. Coliform levels were statistically different at the 95 percent confidence levels for winter versus summer conditions and dry versus wet weather conditions. Other water quality parameters that varied with season were organic carbon, turbidity, dissolved oxygen, and specific conductance. These results indicate that land use management can be effective for mitigating impacts to a water body; however, year- round, comprehensive data are necessary to thoroughly evaluate the water quality at a particular site. [source] Modelling the occurrence of rainbow lorikeets (Trichoglossus haematodus) in MelbourneAUSTRAL ECOLOGY, Issue 2 2006PAVLINA SHUKUROGLOU Abstract Over the previous three decades, the rainbow lorikeet (Trichoglossus haematodus Family Psittacidae) has increased in urbanized areas of Australia. To help understand the nature of this increase, we investigated the influence of road density, tree cover and season on the occurrence of the rainbow lorikeet in the Melbourne region. Bayesian logistic regression was used to construct models to predict the occurrence of rainbow lorikeets, using Birds Australia atlas data at 207 2-ha sites. The results demonstrate a strong relationship between tree cover and urbanization and the distribution of the species. The best model incorporated quadratic terms for road density and tree cover, and interaction terms, as well as season as a categorical variable. Probability of occurrence of rainbow lorikeets was highest at medium tree cover (40% to 70% of the site covered) and medium road density (9% to 12% of the surrounding area covered by roads). There was a close correspondence between the predictions of the model and new observations from bird surveys conducted at randomly selected field sites. The increased abundance of the species in urban areas has occurred despite a paucity of hollows that would act as suitable nesting sites, suggesting that only a small proportion of the population is breeding in these areas. [source] Factors affecting the occupation of a colony site in Sydney., New South Wales by the Grey-headed Flying-fox Pteropus poliocephalus (Pteropodidae)AUSTRAL ECOLOGY, Issue 1 2001K. A. PARRY-JONES Abstract Previous authors have reported that Pteropus poliocephalus colony sites are occupied in response to blossom availability. However, in the present study it is reported that at the Gordon site in suburban Sydney, colony numbers were negatively correlated with the occurrence of pollen in the droppings. In addition, in contrast to reported occupational patterns at other colony sites, where flying-foxes are not present at the site during winter and early spring, the Gordon site was occupied by substantial numbers of flying-foxes throughout the entire period of 62 months from 1985 to 1990. As a result of the introduction of plants native to other parts of Australia and exotics from other continents, there is a variety of foods available throughout the year in the Sydney region, in comparison with less urbanized areas. This food supply permits the occupation of the Gordon colony site during winter and spring and reduces the migratory behaviour of flying-foxes throughout the year. It is concluded that in the absence of a restrictive food supply, the occupational pattern of the Gordon colony of P. poliocephalus is the result of the reproductive requirements of the species modified by the vagaries of blossom production in the native forests outside the foraging range of the colony. [source] Factors affecting the occupation of a colony site in Sydney, New South Wales by the Grey-headed Flying-fox Pteropus poliocephalus (Pteropodidae)AUSTRAL ECOLOGY, Issue 1 2001K. A. Parry-Jones Abstract Previous authors have reported that Pteropus poliocephalus colony sites are occupied in response to blossom availability. However, in the present study it is reported that at the Gordon site in suburban Sydney, colony numbers were negatively correlated with the occurrence of pollen in the droppings. In addition, in contrast to reported occupational patterns at other colony sites, where flying-foxes are not present at the site during winter and early spring, the Gordon site was occupied by substantial numbers of flying-foxes throughout the entire period of 62 months from 1985 to 1990. As a result of the introduction of plants native to other parts of Australia and exotics from other continents, there is a variety of foods available throughout the year in the Sydney region, in comparison with less urbanized areas. This food supply permits the occupation of the Gordon colony site during winter and spring and reduces the migratory behaviour of flying-foxes throughout the year. It is concluded that in the absence of a restrictive food supply, the occupational pattern of the Gordon colony of P. poliocephalus is the result of the reproductive requirements of the species modified by the vagaries of blossom production in the native forests outside the foraging range of the colony. 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