Hydrologic Modeling Uncertainty Resulting From Land Cover Misclassification1

Abstract: A stochastic, spatially explicit method for assessing the impact of land cover classification error on distributed hydrologic modeling is presented. One‐hundred land cover realizations were created by systematically altering the North American Landscape Characterization land cover data according to the dataset’s misclassification matrix. The matrix indicates the probability of errors of omission in land cover classes and is used to assess the uncertainty in hydrologic runoff simulation resulting from parameter estimation based on land cover. These land cover realizations were used in the GIS‐based Automated Geospatial Watershed Assessment tool in conjunction with topography and soils data to generate input to the physically‐based Kinematic Runoff and Erosion model. Uncertainties in modeled runoff volumes resulting from these land cover realizations were evaluated in the Upper San Pedro River basin for 40 watersheds ranging in size from 10 to 100 km² under two rainfall events of differing magnitudes and intensities. Simulation results show that model sensitivity to classification error varies directly with respect to watershed scale, inversely to rainfall magnitude and are mitigated or magnified by landscape variability depending on landscape composition.     

塔里木盆地北缘盐渍地遥感调查及成因分析——以渭干河-库车河三角洲绿洲为例

土壤盐渍化严重威胁着干旱区绿洲的稳定与可持续发展，因此监测盐渍地的分布范围和程度以及分析其成因有着重要的意义。以塔里木盆地北缘盐渍地普遍发育区域渭干河-库车河三角洲绿洲为例，利用TM遥感影像，在野外调查的基础上，采用监督分类中的波谱角度分类法进行了盐渍地调查研究。该方法对盐渍地的提取精度可达到92％左右，是干旱区盐渍地监测的一种有效方法。在此基础上分析了渭干河-库车河三角洲绿洲盐渍地的分布范围与程度，并结合气候、地貌、水文、人类活动等因素，对盐渍化成因进行了讨论。结果表明：干旱荒漠气候是形成盐渍地的前提条件，母岩和母质含盐是形成盐渍地的物质基础，地表水和地下水的补给是形成盐渍地的动力，人为因素是形成灌区次生盐渍地的重要条件。     

面向防洪救灾的人口空间分布模拟——以大安市为例

人是最重要的受灾体，准确的人口空间模拟是衡量洪涝灾情和实施防灾救灾的重要依据。利用遥感数据模拟人口空间分布需解决两大难题：（1）居民地类型、面积、位置的精确获取；（2）居民地类型、面积与人口数量的关系。基于地理意义和数学意义，对经典的城市人口一面积异速生长模型进行了扩展，导出了城乡人口一面积统一模型；并以大安市为例，建立了居民地分类体系，以1：5万地形图为辅助数据，利用ETM影像提取居民地信息，在上述模型的基础上建立了人口分布的反演模型，模拟人口的空间分布。通过精度评价，进一步证明了基于遥感数据的人口统计数据空间化的研究思路是切实可行的。     

中国北方沙质荒漠化土地动态变化遥感分析

采用1975年MSS卫星图像、2000年ETM卫星图像为遥感信息源,结合地理信息系统方法,通过建立科学的沙质荒漠化土地类型和动态变化类型分类系统,对我国北方地区近25年来的沙质荒漠化土地进行了动态变化分析.结果表明:沙质荒漠化土地呈明显的发展状态,其面积明显增加,强度明显增大.其面积增加了7 369.71km 2,平均每年增加294.79km 2,发展区面积90 663.90km 2,稳定区面积140 167.06 km 2,逆转区面积69 147.33km 2,发展区的面积比逆转区的面积大21 516.57km 2.总体呈现"整体发展,局部逆转"和"面上破坏,点上治理"的变化特点.     

Rapid Assessment of Soil Erosion in the Rio Lempa Basin, Central America, Using the Universal Soil Loss Equation and Geographic Information Systems

Soil erosion is a severe problem for many developing regions that lack adequate infrastructure to combat the problem. The authors established a first-order method for prioritizing areas to be examined and remediated using preexisting data and expert knowledge where data are lacking. The Universal Soil Loss Equation was applied to the Rio Lempa Basin in Central America using geographic information systems and remote sensing technologies, and the estimated erosion rates were compared with sediment delivery ratios. Spatial analysis indicates that agriculture on very steep slopes contributes only a small fraction to the total estimated soil erosion, whereas agriculture on gentle and moderately steep slopes contributes a large fraction of the erosion. Although much of the basin is in El Salvador, the greatest estimated amount of erosion is from Honduras. Data quality and availability were impaired by a lack of coordination among agencies and across countries. Several avenues for improving the authors’ methods are described.     

Identification of Land-Cover Changes Through Image Processing and Associated Impacts on Water Reservoir Conditions

A temporal assessment of land-cover changes of the province Beykoz in Istanbul has been documented in this article. The study focuses on the acquisition and analysis of LANDSAT 5 TM images that reflect the drastic land-cover changes between the years 1984 and 2001 utilizing aerial photographs, orthophoto maps, standard topographic maps, and ground truth measurements. The status of the province, including its surrounding villages, were examined together with more specialized maps showing only the city center and part of the province that lies within the watershed of the Elmali Drinking Water Reservoir. The land distribution profiles were also calculated for each of the images to help authorities and decision-makers to better understand the main causes of such remarkable changes and to inform them of the changing quality conditions of the reservoir. Rapid, uncontrolled, and illegal urbanization accompanied by insufficient infrastructure has caused degradation of forests and barren lands in the province, especially within the past two decades. The proximity of the province to the reservoirs watershed, downtown Istanbul, and the transportation network has accelerated the land-cover changes whose adverse impacts on the reservoir water quality are sensed. It is intended that the data gathered and processed in this study will provide a basis for future sustainable urban planning and management activities.     

Land-Use and Land-Cover Change in Montane Mainland Southeast Asia

This paper summarizes land-cover and land-use change at eight sites in Thailand, Yunnan (China), Vietnam, Cambodia, and Laos over the last 50 years. Project methodology included incorporating information collected from a combination of semiformal, key informant, and formal household interviews with the development of spatial databases based on aerial photographs, satellite images, topographic maps, and GPS data. Results suggest that land use (e.g. swidden cultivation) and land cover (e.g. secondary vegetation) have remained stable and the minor amount of land-use change that has occurred has been a change from swidden to monocultural cash crops. Results suggest that two forces will increasingly determine land-use systems in this region. First, national land tenure policies—the nationalization of forest lands and efforts to increase control over upland resources by central governments—will provide a push factor making it increasingly difficult for farmers to maintain their traditional swidden land-use practices. Second, market pressures—the commercialization of subsistence resources and the substitution of commercial crops for subsistence crops—will provide a pull factor encouraging farmers to engage in new and different forms of commercial agriculture. These results appear to be robust as they come from eight studies conducted over the last decade. But important questions remain in terms of what research protocols are needed, if any, when linking social science data with remotely sensed data for understanding human-environment interactions.     

Testing the Use of a Land Cover Map for Habitat Ranking in Boreal Forests

Habitat loss and modification is one of the major threats to biodiversity and the preservation of conservation values. We use the term conservation value to mean the benefit of nature or habitats for species. The importance of identifying and preserving conservation values has increased with the decline in biodiversity and the adoption of more stringent environmental legislation. In this study, conservation values were considered in the context of land-use planning and the rapidly increasing demand for more accurate methods of predicting and identifying these values. We used a k-nearest neighbor interpreted satellite (Landsat TM) image classified in 61 classes to assess sites with potential conservation values at the regional and landscape planning scale. Classification was made at the National Land Survey of Finland for main tree species, timber volume, land-use type, and soil on the basis of spectral reflectance in satellite image together with broad numerical reference data. We used the number and rarity of vascular plant species observed in the field as indicators for potential conservation values. We assumed that significant differences in the species richness, rarity, or composition of flora among the classes interpreted in the satellite image would also mean a difference in conservation values among these classes. We found significant differences in species richness among the original satellite image classes. Many of the classes examined could be distinguished by the number of plant species. Species composition also differed correspondingly. Rare species were most abundant in old spruce forests (>200 m³/ha), raising the position of such forests in the ranking of categories according to conservation values. The original satellite image classification was correct for 70% of the sites studied. We concluded that interpreted satellite data can serve as a useful source for evaluating habitat categories on the basis of plant species richness and rarity. Recategorization of original satellite image classification into such new conservation value categories is challenging because of the variation in species composition among the new categories. However, it does not represent a major problem for the purposes of early-stage land-use planning. Benefits of interpreted satellite image recategorization as a rapid conservation value assessment tool for land-use planners would be great.     

The Assessment of Atmospheric Pollution using Satellite Remote Sensing Technology in Large Cities in the Vicinity of Airports

This paper investigates the potential of usingsatellite remotely sensed imagery for assessing atmosphericpollution. A novel approach, which comprised radiativetransfer calculations and pseudo-invariant targets fordetermining aerosol optical thickness has been developed.The key parameter for assessing atmospheric pollution inphotochemical air pollution studies is the aerosol opticalthickness. The need for identifying suitable pseudo-invariantobjects in satellite images of urban areas is of great interest for increasing the potential of earthobservation for monitoring air pollution in such areas. Theidentification of large water bodies and concrete apronsthat can serve as suitable dark and bright targetsrespectively in different geographical areas wasdemonstrated in this study. This study added evidence onthe correlation found between the visibility valuesmeasured at Heathrow Airport area during satellite overpassand aerosol optical thickness derived from Landsat-5 TMband 1 images.     

遥感技术在灾害监测中的应用

介绍总结了近年来遥感技术在灾害监测中的应用与进展，以若干应用实例阐明了遥感技术在实现对自然灾害进行宏观、实时、动态、连续监测中不可替代的作用；在对我国灾害遥感的应用现状进行了分析之后，发现灾前预测工作有所不足；指出遥感技术将进一步同地理信息系统技术和全球定位系统技术相结合，在防灾减灾工作中发挥愈来愈重要的作用。