西北小城镇的震害特点及防灾减灾

西北小城镇面临的地震高风险已成为人们关注的焦点。由于自然环境差、社会经济和城镇基础设施薄弱、民众文化素质低,加大了小城镇抢险救援的难度。另一方面,人口密度低、自救互救能力较强、震后引发的社会问题不突出,又成为有利的一面。了解西北小城镇的震害特点,有针对性地建立起防灾减灾对策,做好平时准备、震前防御、震时救援、震后重建的立体战略思想、战术和方法,就能很好地提高西北小城镇的综合防灾能力。     

The practice of DEM stream burning revisited

Stream burning is a common flow enforcement technique used to correct surface drainage patterns derived from digital elevation models (DEM). The technique involves adjusting the elevations of grid cells that are coincident with the features of a vector hydrography layer. This paper focuses on the problematic issues with common stream burning practices, particularly the topological errors resulting from the mismatched scales of the hydrography and DEM data sets. A novel alternative stream burning method is described and tested using five DEMs of varying resolutions (1 to 30 arc‐seconds) for an extensive area of southwestern Ontario, Canada. This TopologicalBreachBurn method uses total upstream channel length (TUCL) to prune the vector hydrography layer to a level of detail that matches the raster DEM grid resolution. Network pruning reduces the occurrence of erroneous stream piracy caused by the rasterization of multiple stream links to the same DEM grid cell. The algorithm also restricts flow within individual stream reaches, further reducing erroneous stream piracy. In situations where two vector stream features occupy the same grid cell, the new tool ensures that the larger stream, designated by higher TUCL, is given priority. TUCL‐based priority minimizes the impact of the topological errors that occur during the stream rasterization process on modeled regional drainage patterns. The test data demonstrated that TopologicalBreachBurn produces highly accurate and scale‐insensitive drainage patterns and watershed boundaries. The drainage divides of four large watersheds within the study region that were delineated from the TopologicalBreachBurn‐processed DEMs were found to be highly accurate when compared with the official watershed boundaries, even at the coarsest grid resolutions, with Kappa index of agreement values ranging from 0.952 to 0.921. The corresponding Kappa coefficient values for a traditional stream burning method (FillBurn) ranged from 0.953 to 0.490, demonstrating a significant decrease in mapping accuracy at coarser DEM grid resolutions. Copyright © 2015 John Wiley & Sons, Ltd.     

Ranking spaces for predicting human movement in an urban environment

A city can be topologically represented as a connectivity graph, consisting of nodes representing individual spaces and links if the corresponding spaces are intersected. It turns out in the space syntax literature that some defined topological metrics can capture human movement rates in individual spaces. In other words, the topological metrics are significantly correlated to human movement rates, and individual spaces can be ranked by the metrics for predicting human movement. However, this correlation has never been well justified. In this paper, we study the same issue by applying the weighted PageRank algorithm to the connectivity graph or space–space topology for ranking the individual spaces, and find surprisingly that: (1) the PageRank scores are better correlated to human movement rates than the space syntax metrics, and (2) the underlying space–space topology demonstrates small world and scale free properties. The findings provide a novel justification as to why space syntax, or topological analysis in general, can be used to predict human movement. We further conjecture that this kind of analysis is no more than predicting a drunkard's walking on a small world and scale free network.     

Range imaging: a new method for high‐resolution topographic measurements in small‐ and medium‐scale field sites

Topographic measurements are essential for the study of earth surface processes. Three‐dimensional data have been conventionally obtained through terrestrial laser scanning or photogrammetric methods. However, particularly in steep and rough terrain, high‐resolution field measurements remain challenging and often require new creative approaches. In this paper, range imaging is evaluated as an alternative method for obtaining surface data in such complex environments. Range imaging is an emerging time‐of‐flight technology, using phase shift measurements on a multi‐pixel sensor to generate a distance image of a surface. Its suitability for field measurements has yet not been tested. We found ambient light and surface reflectivity to be the main factors affecting error in distance measurements. Low‐reflectivity surfaces and strong illumination contrasts under direct exposure to sunlight lead to noisy distance measurements. However, regardless of lighting conditions, the accuracy of range imaging was markedly improved by averaging multiple images of the same scene. For medium ambient lighting (shade) and a light‐coloured surface the measurement uncertainty was approximately 9 mm. To further test the suitability of range imaging for field applications we measured a reach of a steep mountain stream with a horizontal resolution of approximately 1 cm (in the focal plane of the camera), allowing for the interpolation of a digital elevation model on a 2 cm grid. Comparison with an elevation model obtained from terrestrial laser scanning for the same site revealed that both models show similar degrees of topographic detail. Despite limitations in measurement range and accuracy, particularly at bright ambient lighting, range imaging offers three‐dimensional data in real time and video mode without the need of post‐processing. Therefore, range imaging is a useful complement or alternative to existing methods for high‐resolution measurements in small‐ to medium‐scale field sites. Copyright © 2012 John Wiley & Sons, Ltd.     

Pesticides Removal by Filtration over Cactus Pear Leaves: A Cheap and Natural Method for Small‐Scale Water Purification in Semi‐Arid Regions

This study aims to examine the efficiency of Opuntia ficus‐indica for removing organochlorine pesticides from surface waters. Adsorption properties such as size, dose, and time of O. ficus‐indica for aldrin, dieldrin, and dichlorodiphenyltrichloroethane (DDT) were studied through stirring and column methods. Because of their high affinity and swelling characteristics, dried O. ficus‐indica was studied in stirring while fresh unpeeled O. ficus‐indica was applied in both stirring and column experiments and proved to be well‐suited to column application. Before removing pesticides, the column was flashed with distilled water eliminate the turbidity and smell from fresh unpeeled cactus. The removal of pesticides increased with an increasing adsorbent dose and decreased with adsorbent particle sizes. The optimum adsorbent dose is 10 g for dried and 15 g for fresh unpeeled O. ficus‐indica. The experimental results show that O. ficus‐indica possesses strong adsorption ability for aldrin, dieldrin, and DDT, and the adsorption isotherm data obeyed the Freundlich model. The results of our small‐scale experiments suggest a strong potential to develop local small‐scale water treatment units that can be used at the level of individual households or local communities, using a widely available adsorbent.     

The geographic distribution of small dams in Oregon using ecoregion and landform classification

Abstract

Small dams fragment river landscapes, disrupting channel connectivity and impacting water quality and quantity. Although they impound volumetrically less total water than large dams, the ubiquity of small dams suggests their cumulative impacts could be significant. Documenting the distribution and characteristics of small dams is necessary to understanding and mitigating their impacts. In this study, we compare datasets of small dams in Oregon, compile a new comprehensive dataset, and document geographic variations in small dam distributions between different ecoregions. We used Oregon Water Resources Department dam and Oregon Department of Fish and Wildlife fish passage barrier datasets to compare dam heights and contributing drainage areas between different ecoregions. Over 61% of Oregon’s land area is above one or more small dam. We highlight the location of Oregon’s small dams at valley margins, transition zones between flat plains and mountains, and areas of high population density. Given the hidden nature of small dams, evaluation of small dam impacts using public imagery is not effective. However, knowledge of small dam distributions given their association with landforms can aid in finding unrecorded dams, assessing approaches for evaluating their geomorphic impacts, and informing their management.     

Understanding interlinkages between long-term trajectory of exposure and vulnerability,path dependency and cascading impacts of disasters in Saint-Martin (Caribbean)

This empirical and interdisciplinary study investigates the contribution of deeply enrooted social-political factors to the accumulation of exposure and vulnerability and amplification of cascading impacts of disasters, with implications on the creation and reinforcement of path dependency maintaining social-ecological systems on a maladaptive trajectory. Applying the Trajectory of Exposure and Vulnerability approach to Saint-Martin (Caribbean), we more specifically highlight how the causal chain linking historical geopolitical and political-institutional drivers to legal, economic, demographic, sociocultural, planning-related and environmental drivers, created the accumulation of exposure and vulnerability over time and contributed to the propagation and amplification of the impacts of tropical cyclones Irma and José in 2017. We find that historical social-political dynamics involving unsustainable development and settlement patterns, the weakness of local institutions, population mistrust in public authorities, high social inequalities and environmental degradation maintained Saint-Martin on a maladaptive trajectory through powerful reinforcing mechanisms operating both between and during cyclonic events. This study demonstrates that long-term interdisciplinary approaches are required for a better understanding of path dependency and the identification of levers to break it in risk-prone contexts. In Saint-Martin, breaking path dependency requires the alignment of local institutional capacities with national risk reduction policies, the promotion of social justice and involvement of local communities in decision making. This study therefore confirms the relevance of backward-looking approaches to support forward-looking climate adaptation.     

Ecological quality assessment of small estuaries from the Portuguese coast based on fish assemblages indices

The importance of establishing the ecological quality of estuarine systems has been widely acknowledged and led to the development of several fish community-based multimetric indices. Nevertheless, a question rose about the accuracy of these tools when natural disturbance is acting upon the organization of the systems’ communities. Four multimetric indices were used to examine their ability to differentiate the ecological status of five small estuarine systems (southern Portugal), and also to test if they reflected the level of anthropogenic pressures. Fish assemblages from Mira, Odeceixe and Aljezur (in the Southwest coast), Gilão and Bensafrim (in the South coast) estuaries were sampled seasonally for one year, and anthropogenic sources of pressure were identified and quantified. We found that although the applied indices provided information on ecological condition differentiation among systems, they are unable to explain different classes of ecological status in systems with equivalent pressure levels.     

Growth, condition and energy stores of Arctic grayling fry inhabiting natural and artificial constructed Arctic tundra streams

Juvenile north-temperate and Arctic fishes are faced with trade-offs between energy allocation to growth and energy storage (primarily lipids) prior to over-wintering. We determined classical morphometric (fork length, body weight and condition factor) and biochemical (whole body triglycerides, muscle RNA/DNA ratio, muscle proteins) measures of growth and condition in individual young-of-the-year (YOY) Arctic grayling (Thymallus arcticus). Grayling were collected just prior to over-wintering in late August (approximately 50 days after swim-up) from two natural streams and five locations within a 3.4 km long artificial stream constructed as a fish habitat compensation project and diversion channel for the diamond mining industry in Northwest Territories, Canada (64°45′N). Fork lengths, body weights and whole body triglyceride levels in grayling collected from all sites along the artificial stream were significantly lower than fish collected from one of the natural streams. Condition factor (weight-at-length) was not different among grayling collected from natural and artificial streams. Muscle proteins were lower in grayling collected from four sites along the artificial stream compared to the natural streams. In contrast, muscle RNA/DNA ratios were greater in grayling collected from two sites in the artificial stream compared to natural streams. There were no consistent differences in any variable among grayling collected at the five artificial stream sites or among grayling collected from the two natural streams. The higher RNA/DNA ratios and lower fork lengths, whole body triglycerides and muscle proteins in grayling inhabiting the artificial stream are consistent with energy still being primarily allocated to growth in these fish at this late stage of summer. Individuals that are both larger and possess greater energy storage in the form of triglycerides are more likely to survive the long over-wintering period at this latitude. Our results suggest that YOY grayling using the artificial stream as nursery habitat will likely face increased over-winter mortality, thus raising concerns over the use of fish presence, spawning and rearing as criteria for the initial success of artificial streams as habitat compensation measures in Arctic tundra regions. Further research is needed to determine the potential consequences of reduced size and energy storage in juvenile fishes in order to assess the viability of stream fish habitat compensation and restoration projects associated with industrial development in Arctic tundra regions.     

霍山皖33井水位与"霍山窗"小震活动关系的初步研究

分析了霍山皖33井水位变化与"霍山窗"地震活动的关系:首先采用差分法和从属函数等方法对水位数据进行处理,提取了水位的短期异常,结果表明该井水位异常对霍山以及周边地区的中小地震有较好的反映;其次,通过对该井水位与"霍山窗"小震活动性的对比研究,发现该地区小地震在水位低值时活跃.参考该地区的环境剪应力,我们认为霍山皖33井...