Land-cover change in upper Barataria Basin estuary,Louisiana, 1972-1992: increases in Wetland area

The Barataria Basin, Louisiana, USA, is an extensive wetland and coastal estuary system of great economic and intrinsic value. Although high rates of wetland loss along the coastal margin of the Barataria Basin have been well documented, little information exists on whether freshwater wetlands in the upper basin have changed. Our objectives were to quantify land-cover change in the upper basin over 20 years from 1972–1992 and to determine land-cover transition rates among land-cover types. Using 80-m resolution Landsat MSS data from the North American Landscape Characterization (NALC) data archive, we classified images from three time steps (1972, 1985, 1992) into six land-cover types: agriculture, urban, bottomland hardwood forest, swamp forest, freshwater marsh, and open water. Significant changes in land cover occurred within the upper Barataria Basin over the study period. Urban land increased from 8% to 17% of the total upper basin area, primarily due to conversions from agricultural land, and to a lesser degree, bottomland forest. Swamp forest increased from 30% to 41%, associated with conversions from bottomland hardwood forest and freshwater marsh. Overall, bottomland forest decreased 38% and total wetland area increased 21%. Within the upper Barataria, increases in total wetland area may be due to land subsidence. Based on our results, if present trends in the reduction of bottomland forest land cover were to continue, the upper Barataria Basin may have no bottomland hardwood forests left by the year 2025, as it is subjected to multiple stressors both in the higher elevations (from urbanization) and lower elevations (most likely from land subsidence). These results suggest that changes in the upper freshwater portions of coastal estuaries can be large and quite different from patterns observed in the more saline coastal margins.     

Trends in the Water Chemistry of High Altitude Lakes in Europe

Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984–1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions.     

遥感在滑坡调查中的应用

本文介绍了遥感技术在滑坡的现状调查和防治中的应用.提出了航天、航空遥感图像上滑坡现状、规模、易滑地点、稳定性评价等的直接和间接判读标志;并展望了遥感技术在滑坡动态监测中的应用前景.     

Monitoring Forest Carbon Sequestration with Remote Sensing and Carbon Cycle Modeling

Sources and sinks of carbon associated with forests depend strongly on the management regime and spatial patterns in potential productivity. Satellite remote sensing can provide spatially explicit information on land cover, stand-age class, and harvesting. Carbon-cycle process models coupled to regional climate databases can provide information on potential rates of production and related rates of decomposition. The integration of remote sensing and modeling thus produces spatially explicit information on carbon storage and flux. This integrated approach was employed to compare carbon flux for the period 1992–1997 over two 165-km² areas in western Oregon. The Coast Range study area was predominately private land managed for timber production, whereas the West Cascades study area was predominantly public land that was less productive but experienced little harvesting in the 1990s. In the Coast Range area, 17% of the land base was harvested between 1991 and 2000. Much of the area was in relatively young, productive-age classes that simulations indicate are a carbon sink. Mean annual harvest removals from the Coast Range were greater than mean annual net ecosystem production. On the West Cascades study area, a relatively small proportion (< 1%) of the land was harvested and the area as a whole was accumulating carbon. The spatially and temporally explicit nature of this approach permits identification of mechanisms underlying land base carbon flux. Published online     

基于3S技术的地质灾害易损性面评价研究

以等面积法作为基本手段,结合3S(GIS、RS、GPS)技术探讨地质灾害易损性面评价的实现方法。提出了为实现易损性面评估而确立的评价对象的分类方法、空间数据库的建设方法、基于空间数据库的空间分析方法以及信息的集成方法。最后探讨了在GIS环境下的数据可视化表达方式和实现地质灾害易损性面评价的一般操作流程。     

印度大地震的可预警信息研究

20 0 1 0 1 2 6印度西北部的普杰地区发生了 7 8级强烈地震。对这次强震事件 ,利用卫星遥感监测地气系统射出长波辐射的数值产品资料 ,分析了以普杰为中心整个西亚范围内 ,事件发生前后共计 6个月的月平均辐射场的分布特征及其演变过程。发现自震前 2个月至震时当月 ,普杰地区始终是一个辐射 (热 )场的高值中心 ,震后明显消散。据此认为印度大地震有可识别的预警信息 ,提出利用卫星遥感技术及其产品 ,有可能为“突破”短临地震预报开拓出一种新的预测技术生长点     

基于3S在土地更新调查中的应用

以青海省德令哈市为例,论述在土地利用更新调查中应用新技术的情况,以及利用新技术取得的效果,并阐述了土地利用更新调查和建库的工作流程,同时对新技术和新方法在全省的推广应用提出建议。     

ESTIMATING THE SUSPENDED SEDIMENT LOAD IN RESERVOIRS1

ABSTRACT: The total suspended sediment loads of four north Mississippi reservoirs were determined from measurements of concentrations of suspended sediment in a vertical profile at several locations on each reservoir made during the year. These data were combined with the stage-height and known stage-volume relationships for each reservoir in a numerical integration to determine the total suspended sediment in the water body. Total suspended sediments were estimated using the product of the suspended sediment concentration in the surface water by the appropriate reservoir volume. The averaged ratios of the estimated to measured suspended sediment loads for each reservoir exceeded 0.90. Since the concentration of suspended sediments in surface waters of north Mississippi reservoirs has been shown as highly correlated with spectral reflectance, estimating the total suspended sediment of these reservoirs using remotely sensed spectral reflectance data is possible.     

FLOOD HAZARD STUDIES IN THE MISSISSIPPI RIVER BASIN USING REMOTE SENSING1

ABSTRACT. The Spring 1973 Mississippi River flood was investigated using remotely sensed data from ERTS-1. Both manual and automatic analyses of the data indicate that ERTS-I is extremely useful as a regional tool for flood management. Quantitative estimates of area flooded were made in St. Charles County, Missouri and Arkansas. Flood hazard mapping was conducted in three study areas along the Mississippi River using pre-flood ERTS-1 imagery enlarged to 1:250,000 and 1:100,000 scale. The flood prone areas delineated on these maps correspond to areas that would be inundated by significant flooding (approximately the 100 year flood). The flood prone area boundaries were generally in agreement with flood hazard maps produced by the U. S. Army Corps of Engineers and U. S. Geological Survey although the latter are somewhat more detailed because of their larger scale. Initial results indicate that ERTS-1 digital mapping of flood prone areas can be performed at 1:62,500 which is comparable to some conventional flood hazard map scales.     

EVAPOTRANSPIRATION DYNAMICS AT AN ECOHYDROLOGICAL RESTORATION SITE: AN ENERGY BALANCE AND REMOTE SENSING APPROACH1

ABSTRACT: Little work is reported where spatial methods are employed to monitor evapotranspiration (ET) changes as a result of vegetation and wetland restoration. A remote sensing approach with the Surface Energy Balance Algorithm for Land (SEBAL) for estimating ET at The Nature Conservancy's Glacial Ridge prairie‐wetland restoration site in northwestern Minnesota is presented. The calibrated 24‐hour ET from SEBAL was estimated with an average error of prediction of ?4.3 percent. Monthly, interseasonal, and seasonal ET for the period of June to September (2000 to 2003) from three adjacent land‐uses: a hydrologic control preserved wetland; a treated or restored site; and a nontreated or impacted wetland, were used in the study. Results from comparing ET behavior to the preserve suggest restoration efforts have affected monthly and seasonal ET within the treated site. Spatial average standard deviations of the seasonal ET within the preserve, treated, and nontreated sites give 47.3, 75.7, and 109.9 mm, respectively, suggesting hydrologic stabilization within the treated site. Monthly and interseasonal comparisons show similar behavior to that of the seasonal data, where monthly correlations suggest increasing agreement within the treated site, approaching those within the preserve.