Understanding the Large‐Scale Influence of Levees on Floodplain Connectivity Using a Hydrogeomorphic Approach

The widespread construction of levees has reduced river–floodplain connectivity and altered associated fluvial processes in many river systems. Despite the recognition that levees can alter floodplain connectivity, few studies have examined the role of levees in reducing floodplain areas at large watershed scales. This paper explores the application of a hydrogeomorphic floodplain inundation model in the Wabash Basin, located in the Midwestern United States, to assess changes in floodplain area in levee‐protected areas. We evaluate 10‐ and 30‐m topographic resolutions and spatially examine the influence of levees on floodplain area in relation to river network attributes. Generally, floodplains in levee‐protected areas were influenced by topographic resolution, stream order, and elevation details of levees found in topography datasets. We show, when compared to Federal Emergency Management Agency maps, our approach underpredicts floodplain area when using 10‐m resolution topography data but only slightly overpredicts when using 30‐m resolution data. After removing details of levees from topography data, we found changes in floodplain area varied spatially, but basin‐aggregate results changed little compared to topography datasets that contain levees, though larger floodplain areas were produced in some regions where levees were removed. This work contributes to a growing research emphasis on using hydrogeomorphic floodplain models to understand floodplain disconnectivity.     

基于GIS的矿山塌陷损害评价系统及可视化方法

在各种工程塌陷问题中,矿山开采引起的地表塌陷是最为严重的一类,矿山塌陷是工程防灾减灾的重要内容。本文围绕“基于GIS的矿山塌陷损害评价系统”的构筑问题,对矿山开采塌陷的三维计算方法和塌陷数据的组织及可视化方式进行了探讨,给出了丘陵和低平山地条件下地表塌陷的三维可视化预计方法,实现了DEM和地表塌陷盆地的可视化表达,并对三维地形图与三维塌陷图的可视化叠置进行了探索。     

基于DEM的黄土高原典型流域水系分形特征研究

基于地理信息系统方法和Horton水系定律,对黄土高原地区葫芦河流域的水系分形特征进行了探讨。研究表明,葫芦河流域正处于流域发展的幼年期。这一时期水系尚未充分发育,下切侵蚀强烈。对流域系统地貌信息熵的判读验证了这一结论。这一结论说明利用分形理论来研究黄土高原典型流域地貌是可能的,深入发展分形方法对于流域地貌研究有重要意义。     

基于DEM的太湖流域水文特征提取

文章选取太湖流域作为研究对象,采用1：25万中比例尺DEM作为基础数据,应用ESRI公司开发的ArcGIS地理信息系统软件进行流域水文特征提取,得到了研究区域水流流向、汇流栅格生成、河网水系、子流域边界等流域特征信息,经与标准河流水系特征对照,认为基于DEM提取的太湖流域水文特征信息是合理的,可作为基础信息,为太湖流域生态环境治理实践及理论研究提供数据支撑。     

生态恢复背景下关中地区城镇与植被空间优化协调研究

针对关中地区城市化土地利用与生态建设的关系,利用2000年和2008年的TM、ETM+与MODIS影像,在不同尺度的格网下,基于土地利用度、生态位理论、廊道与点轴理论,并采用对山脊线山谷线提取的方法,从格局、过程和机理等角度进行研究,实现区域格局优化,并进行功能分区。研究结论如下:①研究区2000—2008年东部与中部土地利用程度增加、西部与南北部分土地利用程度下降,而LAI整体上增加显著,城市发展与植被恢复相对协调;②基于空间生态位理论,绝大多数区县的现实生态位都超过基础生态位的50%,表明调控可从区县所辖乡镇进行,并按照现实生态位范围进行城市发展阻力测算;③选用基于DEM的山脊线山谷线提取方法,获得关中地区景观生态廊道、城市发展轴线和缓冲区,并据此将研究区乡镇分为城市扩展型、双轨并重型、生态建设型。     

SENSITIVITY CONSIDERATIONS WHEN MODELING HYDROLOGIC PROCESSES WITH DIGITAL ELEVATION MODEL1

ABSTRACT: The purpose of this paper is to investigate the sensitivity of a hydrologic models to the type of DEM used. This was done while modeling basin water quality with 1:24,000 and 1:250,000 U.S. Geological Survey DEMs as input to model hydro‐logical processes. The manner in which the model results were sensitive to the choice of raster cell size (scale) is investigated in this study. The Broadhead watershed, located in New Jersey, USA, was chosen as a study area. Curve numbers were estimated by a trial and error to match simulated and observed total discharge. Monthly runoff for the watershed was used in the calibration process. Higher runoff volumes were simulated by the model when the 1:24,000 DEM were used as input data, probably due to the finer resolution which simulated increased average slope and hence higher estimated runoff from the watershed. As the simulated slope of the watershed is flatten with the 1:250,000 DEM, the response of stream flow was delayed and simulated less runoff volume.     

输入数据精度与准确性对SWAT模型模拟的影响

以潮河流域为研究区域,利用潮河流域1990~2013年监测数据,构建SWAT模型,在模型结构和参数不改变的情况下,探究输入数据精度（DEM分辨率）与准确性（降水插值）对径流和总氮模拟结果影响.结果显示：DEM分辨率变化（30~300m）对径流及总氮模拟效果不同,对径流模拟影响不明显,纳什系数（ENS）和R²可达到0.87以上;对总氮模拟结果影响较大,分辨率越精细,模拟效果越好.不同水文年,DEM分辨率变化对总氮负荷模拟表现不同.丰水年对总氮负荷影响较大,负荷量差异较为明显,枯水年影响相对较小;不同DEM分辨率下,年均（1993~2002年）总氮负荷强度空间分布相似,高负荷区均位于潮河中游,潮河上游及下游的负荷强度相对较低.不同降水输入数据站点分布、站网密度和准确性不同,流域内降水空间分布差异显著.总体上,基于站点较少的气象站插值数据与雨量站实测降水数据,径流和总氮模拟效果较为接近;基于SWAT官方雨量站插值数据,径流和总氮模拟效果较差.不同降水数据输入情景下,模拟的总氮负荷强度模拟的空间分布差异明显;降水量分布较高的区域,负荷量也较高;不同水文年下,不同降水输入对总氮负荷模拟表现不同.丰水年和枯水年,基于气象站插值数据的总氮模拟结果与基于雨量站实测数据的模拟结果较为接近,而基于SWAT官方雨量站插值的模拟误差较大;平水年,基于SWAT官方雨量站插值的模拟结果较气象站插值数据的模拟结果更好.该研究可为流域开展模型构建提供科学参考和借鉴.     

传播介质特性对爆破振动衰减规律的影响

以《工程岩体分级标准》为依据,量化作为爆破地震波载体的传播介质的特性,并采用离散单元法分析爆破地震波在传播介质中的衰减过程。数值模拟过程中详细阐述了爆破荷载、介质阻尼及相关参数的确定方法,分析了传播介质特性对爆破振动速度衰减规律及萨道夫斯公式中K、α值的影响。研究表明,在爆破荷载作用下,近距范围内爆破振动速度迅速衰减,中远距范围内爆破振动速度衰减趋缓;传播介质为Ⅰ~Ⅲ级岩体时,随着岩体质量降低,K值有增大趋势,对于Ⅳ~Ⅴ级岩体,K值变化没有明确的规律;α值总体上具有随岩体质量降低而增大的趋势,K、α值具有与爆破振动速度近似相同的增减关系。     

A hydrologic network supporting spatially referenced regression modeling in the Chesapeake Bay Watershed

The U.S. Geological Survey has developed a methodology for statistically relating nutrient sources and land-surface characteristics to nutrient loads of streams. The methodology is referred to as SPAtially Referenced Regressions On Watershed attributes (SPARROW), and relates measured stream nutrient loads to nutrient sources using nonlinear statistical regression models. A spatially detailed digital hydrologic network of stream reaches, stream-reach characteristics such as mean streamflow, water velocity, reach length, and travel time, and their associated watersheds supports the regression models. This network serves as the primary framework for spatially referencing potential nutrient source information such as atmospheric deposition, septic systems, point-sources, land use, land cover, and agricultural sources and land-surface characteristics such as land use, land cover, average-annual precipitation and temperature, slope, and soil permeability. In the Chesapeake Bay watershed that covers parts of Delaware, Maryland, Pennsylvania, New York, Virginia, West Virginia, and Washington D.C., SPARROW was used to generate models estimating loads of total nitrogen and total phosphorus representing 1987 and 1992 land-surface conditions. The 1987 models used a hydrologic network derived from an enhanced version of the U.S. Environmental Protection Agency's digital River Reach File, and course resolution Digital Elevation Models (DEMs). A new hydrologic network was created to support the 1992 models by generating stream reaches representing surface-water pathways defined by flow direction and flow accumulation algorithms from higher resolution DEMs. On a reach-by-reach basis, stream reach characteristics essential to the modeling were transferred to the newly generated pathways or reaches from the enhanced River Reach File used to support the 1987 models. To complete the new network, watersheds for each reach were generated using the direction of surface-water flow derived from the DEMs. This network improves upon existing digital stream data by increasing the level of spatial detail and providing consistency between the reach locations and topography. The hydrologic network also aids in illustrating the spatial patterns of predicted nutrient loads and sources contributed locally to each stream, and the percentages of nutrient load that reach Chesapeake Bay.     

中国土地资源生态环境质量状况分析

基于用数字环境模型对中国土地资源生态环境的质量评价,生成了中国土地资源生态环境综合评价图,分析了中国土地资源生态环境等级面积构成及分布状况,得出了中国土地资源生态环境质量最好的地区全部分布在东南沿海和四川盆地区,生态环境最适合人类生存的土地资源仅占我国土地资源总面积的１／３弱,１／３的土地资源面积养活了我国８０％以上的人口