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1.
Landslide stability analysis increasingly utilises high-resolution coupled hydrology–slope stability models (CHASM) to improve stability assessments in areas subject to dynamic pore pressure regimes. In such environments, the estimation of soil hydraulic conductivity (K) is a key parameter but one which is not always readily available or determined with the required resolution. By using basic soil particle-size distribution (PSD) data, we evaluate the microscopic composition of the actual soil, and applying the analytical relations obtain by a Self-Consistent Method (SCM) approach, we determine an appropriate value of K. This is of importance in that it allows within-soil type variability to be reflected in terms of K and hence within the model structure. The SCM methodology is briefly reviewed and an illustrative application is undertaken for a slope typical of Hong Kong. The results show model output sensitivity in terms of moisture content and factor of safety (FOS) when comparing K values determined using the SCM approach and the conventional field determination. In attempting to determine slope hydrological processes and attendant stability conditions, we conclude that the application of SCM approach offers a novel methodology for potentially improving the parameterisation of hydrology–slope stability models.  相似文献   

2.
Abstract

Geographical Information Systems can be used for processing spatial data to assess the risks of environmental contamination. Their use depends upon the amount and quality of available data, the models for interpolation and calculation of health risk, data processing procedures and interactivity. In this study, it is shown that interactive use of GIS is important for obtaining physically relevant results. Three forms of interactivity are distinguished: interactivity by means of user interfacing, interactivity requiring additional information outside GIS and interactivity when changing the use of GIS. Three stages in which interaction with GIS are crucial can be distinguished: application of geostatistics, choice of appropriate models, and decision making. This study focuses on three cases in The Netherlands dealing with soil contamination and soil stress analysis and with implications for risk assessment in which interactivity within GIS is analysed. Emphasis is given to contour volumes of polluted soil, to combine GIS with deterministic models and to apply land use scenarios. Finally, there is a discussion of how some forms of interactivity could be replaced by expert systems.  相似文献   

3.
Stokkan, J. The potential model – an analysis of some methodological problems. Norsk geogr. Tidsskr. 29, 111–132.

The article is concerned with operational problems of the potential model. In connection with a general discussion of operational problems, a base model is constructed. This model is applied to a study area in order to determine the model's sensitivity to the area of the analytical unit, the distance exponent, and distances within the unit. The analysis shows that the potential is to a large degree dependent upon the definition of these three factors.  相似文献   

4.

Ground vibration induced by rock blasting is one of the most crucial problems in surface mines and tunneling projects. Hence, accurate prediction of ground vibration is an important prerequisite in the minimization of its environmental impacts. This study proposes hybrid intelligent models to predict ground vibration using adaptive neuro-fuzzy inference system (ANFIS) optimized by particle swarm optimization (PSO) and genetic algorithms (GAs). To build prediction models using ANFIS, ANFIS–GA, and ANFIS–PSO, a database was established, consisting of 86 data samples gathered from two quarries in Iran. The input parameters of the proposed models were the burden, spacing, stemming, powder factor, maximum charge per delay (MCD), and distance from the blast points, while peak particle velocity (PPV) was considered as the output parameter. Based on the sensitivity analysis results, MCD was found as the most effective parameter of PPV. To check the applicability and efficiency of the proposed models, several traditional performance indices such as determination coefficient (R2) and root-mean-square error (RMSE) were computed. The obtained results showed that the proposed ANFIS–GA and ANFIS–PSO models were capable of statistically predicting ground vibration with excellent levels of accuracy. Compared to the ANFIS, the ANFIS–GA model showed an approximately 61% decrease in RMSE and 10% increase in R2. Also, the ANFIS–PSO model showed an approximately 53% decrease in RMSE and 9% increase in R2 compared to ANFIS. In other words, the ANFIS performance was optimized with the use of GA and PSO.

  相似文献   

5.
《Urban geography》2013,34(7):582-610
This paper examines the geography of violent crime across the neighborhoods of Tucson and South Tucson, Arizona. The research is informed by the tenets of modern social disorganization theory, which has a strong ecological or environmental basis. Three different crime indices are computed; each represents an annual average during the five-year period 1995-1999. The most comprehensive index captures aggravated assaults, homicides, robberies, and sexual assaults. After providing a factor-ecological study of the study area, using 27 variables taken from the 1990 census, various regression models are developed to explain violent crime patterns. These models use a smaller array of ten demographic, economic, and social attributes to predict patterns at the block group level. A number of variables are found to be significant across all models, thereby providing further support for social disorganization theory. Stability in the signs and values of the estimates suggest that a general model of violent crime can be established for the study region. The paper closes with a short discussion of some public policy implications.  相似文献   

6.
Weights-of-evidence (WofE) and logistic regression techniques were used in a GIS framework to predict the spatial likelihood (prospectivity) of crushed-stone aggregate quarry development. The joint conditional probability models, based on geology, transportation network, and population density variables, were defined using quarry location and time of development data for the New England States, North Carolina, and South Carolina, USA. The Quarry Operation models describe the distribution of active aggregate quarries, independent of the date of opening. The New Quarry models describe the distribution of aggregate quarries when they open. Because of the small number of new quarries developed in the study areas during the last decade, independent New Quarry models have low parameter estimate reliability. The performance of parameter estimates derived for Quarry Operation models, defined by a larger number of active quarries in the study areas, were tested and evaluated to predict the spatial likelihood of new quarry development. Population density conditions at the time of new quarry development were used to modify the population density variable in the Quarry Operation models to apply to new quarry development sites. The Quarry Operation parameters derived for the New England study area, Carolina study area, and the combined New England and Carolina study areas were all similar in magnitude and relative strength. The Quarry Operation model parameters, using the modified population density variables, were found to be a good predictor of new quarry locations. Both the aggregate industry and the land management community can use the model approach to target areas for more detailed site evaluation for quarry location. The models can be revised easily to reflect actual or anticipated changes in transportation and population features.  相似文献   

7.
The analysis of rainfall as an environmental factor that influences landscape dynamics is an important and ongoing topic of discussion. This discussion can be centred on the discovery of impacts caused by the increase or decrease in rainfall frequency and intensity. From this perspective, this study sought to analyse the rainfall variability in the Iguaçu River basin, located in the State of Paraná, southern Brazil. The main objective was focused on the temporal-spatial rainfall distribution in the study area and its interaction with landscape dynamics (different land uses). Precipitation data for the period 1988−2018 were obtained from the ‘Águas Paraná’ Institute. To calculate the Concentration Index−CI values of the study area, data analysis was performed using the ‘R’ software with Climatol and Precindicon subroutines of the software, and analysis of Landsat 8 satellite images through ArcGIS. The results indicated that there was a well-defined spatial variability in the study area, as the CIs defined higher rainfall concentrations upstream from the river basin and lower rainfall concentrations downstream—implying that these processes may be strongly associated with land use.  相似文献   

8.
We sampled living and subfossil phantom midge (Diptera: Chaoboridae) larvae from surface sediments of 21 small lakes in Southern Sweden to examine the influence of fish and selected abiotic variables on the abundance and species composition of chaoborid assemblages. We expected total Chaoborus abundance to be inversely correlated with fish abundance and Chaoborus species most sensitive to fish predation to be found only in fishless lakes. We aimed to use the observed relationships to develop models to reconstruct past fish abundances from chaoborid remains and the abiotic environment. C. flavicans occurred in almost every lake, whereas subfossil C. obscuripes were found in the surface sediments of only one fishless lake. The density of living C. flavicans larvae correlated negatively with fish abundance, lake order and size. The concentration of C. flavicans subfossils was negatively associated with pH, lake size, water transparency and fish abundance. Regression models that included lake morphometry and landscape position as additional predictors of fish abundance performed better than models that used only Chaoborus predictors. The explained variance in fish abundance varied from 52 to 86%. Leave-one-out cross-validation indicated moderate performance of the two best models. These models explained 51 and 56% of the observed untransformed fish density and biomass, respectively. In addition, all Chaoborus models were unbiased in closely following the 1:1 reference line in plots of observed versus predicted values. These results are a promising step in developing midge-based paleolimnological reconstructions of past fish abundance, and the approach might be improved by including chironomid remains in the models.  相似文献   

9.
The temperature reconstruction obtained from chironomids preserved in the sediment of Egelsee, Switzerland, was partially flawed by the low percentages of fossil taxa represented in the Swiss calibration set (Larocque-Tobler et al. 2009a). Transfer functions (TFs) from other regions, which allow a good representation of the fossil taxa (>80%), could be applied to the fossil assemblages of Egelsee. First, the validity of using two (a Swedish and a North American (NA)) TFs was tested by comparing the chironomid-inferred temperatures with instrumental data. Since good relationships (r Pearson = 0.71 and 0.61, p = 0.001 for the NA and Swedish TFs, respectively) were obtained, these two models were used to reconstruct the Late Glacial and early Holocene periods at Egelsee. Reconstructions using both models showed clear cold periods during the Younger Dryas and the so-called 8,200 calibrated years BP event. However, the amplitude of changes during these periods was higher when the NA transfer function was used, probably due to the fact that 37% of the taxa in the core had temperature optima colder in the NA than in the Swedish and Swiss models. The results indicate that TFs from other regions can be applied when they are based on samples with good modern analogues, however, caution should be taken when the amplitude of temperature changes is considered.  相似文献   

10.
The effect of topography on moss vegetation is examined to clarify the processes that affect the colonization of polar deserts on continental Antarctica. Data on the presence of the mosses Bryum pseudotriquetrum and Pottia heimii, and relative altitude were recorded. The altitude measurements were used to infer the underlying topographical attributes of the substrate in the study plots. Specifically, the local distribution of moss plants was clarified using the topographical attributes to construct generalized linear mixed models (GLMMs). The models suggested that steep slopes and convex microhabitats within areas of concave general relief (at the plot scale 4 × 4 m) promoted the establishment of moss. This correspondence to general relief was more apparent for B. pseudotriquetrum than for P. heimii. Among the study plots, general relief was found to be an important determinant of the precise spatial distribution of B. pseudotriquetrum. The standard surface estimated using the robust methods presented in this study is shown to be more accurate for describing moss distribution than the prevailing least-squares method.  相似文献   

11.
Location-allocation modeling is an important area of research in spatial optimization and GIScience. A large number of analytical models for location-allocation analysis have been developed in the past 50 years to meet the requirements of different planning and spatial-analytic applications, ranging from the location of emergency response units (EMS) to warehouses and transportation hubs. Despite their great number, many location-allocation models are intrinsically linked to one another. A well-known example is the theoretical link between the classic p-median problem and coverage location problems. Recently, Lei and Church showed that a large number of classic and new location models can be posed as special case problems of a new modeling construct called the vector assignment ordered median problem (VAOMP). Lei and Church also reported extremely high computational complexity in optimally solving the best integer linear programming (ILP) formulation developed for the VAOMP even for medium-sized problems in certain cases.

In this article, we develop an efficient unified solver for location-allocation analysis based on the VAOMP model without using ILP solvers. Our aim is to develop a fast heuristic algorithm based on the Tabu Search (TS) meta-heuristic, and message passing interface (MPI) suitable for obtaining optimal or near-optimal solutions for the VAOMP in a real-time environment. The unified approach is particularly interesting from the perspective of GIScience and spatial decision support systems (DSS) as it makes it possible to solve a wide variety of location models in a unified manner in a GIS environment. Computational results show that the TS method can often obtain in seconds, solutions that are better than those obtained using the ILP-based approach in hours or a day.  相似文献   

12.
The complexity of hydrological processes and lack of data for modeling require the use of specific tools for non-linear natural phenomenon. In this paper, an effort has been made to develop a conjunction model – wavelet transformation, data-driven models, and genetic algorithm (GA) – for forecasting the daily flow of a river in northern Algeria using the time series of runoff. This catchment has a semi-arid climate and strong variability in runoff. The original time series was decomposed into multi-frequency time series by wavelet transform algorithm and used as inputs to artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models. Several factors must be optimized to determine the best model structures. Wavelet-based data-driven models using a GA are designed to optimize model structure. The performances of wavelet-based data-driven models (i.e. WANFIS and WANN) were superior to those of conventional models. WANFIS (RMSE = 12.15 m3/s, EC = 87.32%, R = .934) and WANN (RMSE = 15.73 m3/s, EC = 78.83%, R = .888) models improved the performances of ANFIS (RMSE = 23.13 m3/s, EC = 54.11%, R = .748) and ANN (RMSE = 22.43 m3/s, EC = 56.90%, R = .755) during the test period.  相似文献   

13.
During the last two decades, a variety of models have been applied to understand and predict changes in land use. These models assign a single-attribute label to each spatial unit at any particular time of the simulation. This is not realistic because mixed use of land is quite common. A more detailed classification allowing the modelling of mixed land use would be desirable for better understanding and interpreting the evolution of the use of land. A possible solution is the multi-label (ML) concept where each spatial unit can belong to multiple classes simultaneously. For example, a cluster of summer houses at a lake in a forested area should be classified as water, forest and residential (built-up). The ML concept was introduced recently, and it belongs to the machine learning field. In this article, the ML concept is introduced and applied in land-use modelling. As a novelty, we present a land-use change model that allows ML class assignment using the k nearest neighbour (kNN) method that derives a functional relationship between land use and a set of explanatory variables. A case study with a rich data-set from Luxembourg using biophysical data from aerial photography is described. The model achieves promising results based on the well-known ML evaluation criteria. The application described in this article highlights the value of the multi-label k nearest neighbour method (MLkNN) for land-use modelling.  相似文献   

14.
An augmented scene delivery system (ASDS) creates and distributes annotated cartographic products in real time from captured still imagery. An ASDS applies augmented reality technology to the visualization of unrestricted exterior viewsheds through an adaptive, perspective‐based surface resampling model. This paper describes an ASDS testing platform, introduces a client/server model for distributing augmented scenes over the Internet, presents a linear‐time algorithm for resampling dense elevation models for perspective imaging and conducts an execution analysis of the algorithm's implementation, demonstrating that augmented scenes can be constructed and delivered efficiently. The paper also presents a migration path to mobile ASDS platforms with a discussion of the remaining technological problems associated with its implementation.  相似文献   

15.
容积率对地价的作用机理及实证研究--以南京市为例   总被引：7，自引：0，他引：7  
文章在分析容积率对于城市地价影响的作用机理基础上,应用有关城市土地经济学理论和模型,采用边际分析方法,对南京商业、住宅、工业用地的样点数据进行实证分析。研究结果表明,城市规划与城市地价的相互关系十分复杂,但建立两者相互作用的模型是可行的,同时指出城市规划按地价理论来实施并且通过城市规划的实施促进地价空间的合理分布是必要的。研究地价、城市规划的关系,其意义不仅仅局限于如何在城市规划中充分利用地价理论优化城市土地利用结构、提高土地利用效率,同时也是为了在城市规划工作中寻找内在规律,为编制出最佳的土地利用规划及在城市中形成最佳地价空间分布及地价水平奠定基础。  相似文献   

16.
Landscape metrics have been widely used to characterize geographical patterns which are important for many geographical and ecological analyses. Cellular automata (CA) are attractive for simulating settlement development, landscape evolution, urban dynamics, and land-use changes. Although various methods have been developed to calibrate CA, landscape metrics have not been explicitly used to ensure the simulated pattern best fitted to the actual one. This article presents a pattern-calibrated method which is based on a number of landscape metrics for implementing CA by using genetic algorithms (GAs). A Pattern-calibrated GA–CA is proposed by incorporating percentage of landscape (PLAND), patch metric (LPI), and landscape division (D) into the fitness function of GA. The sensitivity analysis can allow the users to explore various combinations of weights and examine their effects. The comparison between Logistic- CA, Cell-calibrated GA–CA, and Pattern-calibrated GA–CA indicates that the last method can yield the best results for calibrating CA, according to both the training and validation data. For example, Logistic-CA has the average simulation error of 27.7%, but Pattern-calibrated GA–CA (the proposed method) can reduce this error to only 7.2% by using the training data set in 2003. The validation is further carried out by using new validation data in 2008 and additional landscape metrics (e.g., Landscape shape index, edge density, and aggregation index) which have not been incorporated for calibrating CA models. The comparison shows that this pattern-calibrated CA has better performance than the other two conventional models.  相似文献   

17.
Luoto Miska  Hjort Jan 《Geomorphology》2005,67(3-4):299-315
Predictive models are increasingly used in geomorphology, but systematic evaluations of novel statistical techniques are still limited. The aim of this study was to compare the accuracy of generalized linear models (GLM), generalized additive models (GAM), classification tree analysis (CTA), neural networks (ANN) and multiple adaptive regression splines (MARS) in predictive geomorphological modelling. Five different distribution models both for non-sorted and sorted patterned ground were constructed on the basis of four terrain parameters and four soil variables. To evaluate the models, the original data set of 9997 squares of 1 ha in size was randomly divided into model training (70%, n=6998) and model evaluation sets (30%, n=2999).In general, active sorted patterned ground is clearly defined in upper fell areas with high slope angle and till soils. Active non-sorted patterned ground is more common in valleys with higher soil moisture and fine-scale concave topography. The predictive performance of each model was evaluated using the area under the receiver operating characteristic curve (AUC) and the Kappa value. The relatively high discrimination capacity of all models, AUC=0.85–0.88 and Kappa=0.49–0.56, implies that the model's predictions provide an acceptable index of sorted and non-sorted patterned ground occurrence. The best performance for model calibration data for both data sets was achieved by the CTA. However, when the predictive mapping ability was explored through the evaluation data set, the model accuracies of CTA decreased clearly compared to the other modelling techniques. For model evaluation data MARS performed marginally best.Our results show that the digital elevation model and soil data can be used to predict relatively robustly the activity of patterned ground in fine scale in a subarctic landscape. This indicates that predictive geomorphological modelling has the advantage of providing relevant and useful information on earth surface processes over extensive areas, such data being unavailable through more conventional survey methods.  相似文献   

18.
This case study of growth faults and associated deltaic sedimentation in the shallow‐offshore Niger Delta uses an integrated analysis of three‐dimensional (3D)‐seismic coherence facies and wireline data that supports an evaluation of the sedimentary response to delta tectonics. The study area comprises four fault blocks bounded by a set of kilometre‐scale, basinward‐dipping, synsedimentary normal faults. Correlation of highly variable growth stratigraphy across faults was achieved by a systematic visualization and interpretation of series of coherence horizon‐slices: the detection and matching of erosive and depositional patterns (e.g. channels) across faults allowed the establishment of sedimentology‐controlled links between diverse footwall and hanging‐wall growth successions. At the same time, this interpretation approach helped to visualize seismic‐sedimentological and seismic‐geomorphological features survey‐wide at all depth levels. The integration of this extensive 3D database with lithology information from wireline logs provides a powerful tool for subsurface sedimentology interpretation. Synoptic analysis of the 3D‐seismic sedimentology interpretation with stratigraphy based fault‐kinematic analysis using throw vs. depth plots (Th–Z plots) enabled a discussion of the relation between delta tectonics and sedimentary‐system development, and the evaluation of the Th–Z method for subsurface‐lithology prediction. The interpretation results document that both motion analysis of synsedimentary deltaic faults and Th–Z‐based lithology prediction are only feasible when supported by detailed 3D information on palaeoenvironment and palaeotopography at and around studied fault systems. We therefore recommend the use of fast‐track fault‐kinematic and subsurface‐lithology predictions based on Th–Z plots only when supported by comprehensive 3D seismic‐sedimentological interpretations.  相似文献   

19.
Previous studies have shown chironomids to be excellent indicators of environmental change and training sets have been developed in order to allow these changes to be reconstructed quantitatively from subfossil sequences. Here we present the results of an investigation into the relationships between surface sediment subfossil chironomid distribution and lake environmental variables from 42 lakes on the Tibetan Plateau. Canonical correspondence analysis (CCA) revealed that of the 11 measured environmental variables, salinity (measured as total dissolved solids TDS) was most important, accounting for 10.5% of the variance in the chironomid data. This variable was significant enough to allow the development of quantitative inference models. A range of TDS inference models were developed using Weighted Averaging (WA), Partial Least Squares (PLS), Weighted Averaging–Partial Least Squares (WA–PLS), Maximum Likelihood (ML), Modern Analogues Technique (MAT) and Modern Analogues Techniques weighted by similarity (WMAT). Evaluation of the site data indicated that four lakes were major outliers, and after omitting these from the training set the models produced jack-knifed coefficients of determination (r 2) between 0.60 and 0.80, and root-mean-squared errors of prediction (RMSEP) between 0.29 and 0.44 log10 TDS. The best performing model was the two-component WA–PLS model with r 2 jack = 0.80 and RMSEPjack = 0.29 log10 TDS. The model results were similar to other chironomid-salinity models developed in different regions, and they also showed similar ecological groupings along the salinity gradient with respect to freshwater/salinity thresholds and community diversity. These results therefore indicate that similar processes may be controlling chironomid distribution across salinity gradients irrespective of biogeographical constraints. The performance of the transfer functions illustrates that chironomid assemblages from the Tibetan Plateau lakes are clearly sensitive indicators of salinity. The models will therefore allow the quantification of long-term records of past water salinity for lacustrine sites across the Tibetan Plateau, which has important implications for future hydrological research in the region.  相似文献   

20.
Assemblages of subfossil Chaoboridae mandibles from 80 thermally-stratified shield lakes in southern central Canada were examined to explore the influence of subfossil Chaoborus on subfossil Chironomidae-based paleolimnological inference models of deepwater oxygen, as volume-weighted hypolimnetic oxygen (VWHO). Inclusion of subfossil Chaoborus in subfossil Chironomidae-based VWHO models only improved model performance modestly, however it produced substantively better inferences of hypolimnetic oxygen in anoxic lakes, because Chaoborus had a much stronger positive relationship with low VWHO compared to chironomid taxa indicative of anoxic conditions, such as Chironomus. A Chaoborus mandible:Chironomidae head capsule ratio (chaob:chir) may be a useful index in paleolimnological studies, as chaob:chir in a surface sediment training set was significantly related to VWHO, and displayed little co-variation with other limnological variables such as trophic status (e.g. TP, TN) or lake depth (e.g. Z max). Chaob:chir values in a stratigraphic analysis tracked chironomid-inferred VWHO, however the use of chaob:chir in regional ‘top–bottom’ paleolimnological studies must be used with caution.  相似文献   

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