Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100‐year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large‐scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human‐made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.     

Towards a Drought Watch System based on Spatial SPI

Regional Drought can be assessed through various meaningfulprocedures mainly related to the expected consequences. However, a general knowledge of the occurrence of drought, thearea which is affected, its severity and its duration are ofgreat importance for a series of decisions, which may beappropriate for a variety of activities. From the existingsimple and popular indices used for the estimation of drought,the Standardised Precipitation Index, known as SPI, seems to winuniversal applicability. A method based on the estimation of SPIover a geographical area and its use for characterising drought,is presented in this paper. Applications of the method arepresented using a digital terrain model and a simple computercalculating routine. It is shown that the proposed procedurecan be easily applied and can support a Drought Watch System foran area of mesoscale dimensions.     

低空机载LiDAR水面点云自适应分类算法研究

水陆点云分类是DTM生成、河流岸线提取等低空机载LiDAR应用领域面临的新问题,然而在岸滩等复杂扫描场景中,水陆点云的准确分类是一个公认的难题。在分析目前点云分类存在的缺陷基础上,提出了一种多元特征统计的自适应水陆LiDAR点云分类算法,该算法通过分析低空机载LiDAR水面点云的特点,针对性地设计了点云坡度、密度特征描述子;引入贝叶斯定理,建立了高程、坡度、密度隶属度函数;通过水、陆独立样本的t检验,确定隶属度函数的自适应权重;最终得到一个多元特征统计的分类模型,并基于训练样本的概率密度统计,确定了模型的自适应分类阈值。典型应用实例表明,在存在岸滩、内陆平地等复杂地形条件下,新算法都能达到99%以上的水陆点云分类精度。     

Effective Acquisition Protocol of Terrestrial Laser Scanning for Underwater Topography in a Steep Mountain Channel

For better risk management, detailed and quantitative measurement of channel and stream‐bed structure is required to understand and predict water and sediment flow in mountain channels. Our previous research demonstrated good performance of green‐wavelength Terrestrial laser scanning (TLS) for measurement of submerged stream‐bed in a steep mountain channel. This paper examines how the acquisition protocol of TLS affects the accuracy of data collected in the mountain channel. First, it was tested whether varying the scanner height, i.e., incident angle affects the data acquisition in terms of point density and accuracy in the pool unit of step‐pool channel. Then, the effect of varying the minimum point spacing on the derived Digital terrain model (DTM) was examined. It was also analyzed whether a combination of multiple TLS data acquired from different directions would improve the accuracy of data compared to data acquired by a single measurement. Furthermore, TLS data were acquired over a cascade unit of the channel and examined whether TLS is capable of capturing reliable underwater data. All the acquired underwater data by TLS were corrected for water refraction and validated using manual surveyed data. The results showed that the accuracy of derived DTM was improved when the scanner height was increased or data was acquired from multiple directions, however, acquiring denser point cloud with a minimum point spacing of 1 mm did not improve the accuracy of the data. Accuracy of TLS measurement in the cascade unit was considerably lower. Special consideration is required for this area.     

空间多面域面积的统计研究

简述当前测量行业通常采用的统计空间多面域面积的方法及其所存在的弊端。针对这些弊端，以一做过的项目为例，提出通过外业采集空间面域中特征点，采用建立地面数字模型（DTM）的方式，在CAD平台上利用相应的计算机程式，精确的统计出空间多面域的面积。     

三峡水利枢纽工程右岸地下电站主厂房开挖施工测量

主要介绍了三峡水利枢纽工程右岸地下电站主厂房开挖中施工测量的方法和内业成果处理的原理。实践证明,此方法行之有效,大大提高了工作效率。     

LiDAR测量技术在高陂水利枢纽工程中的应用

水利枢纽工程通常具有范围大、地形复杂等特点,应用机载激光雷达(LiDAR)测量技术能快速获取大面积目标空间信息,提高测量效率。机载激光测量(LiDAR)技术是直接采集并获取数码影像数据和激光点云数据,在此基础上经过后期加工和处理,得到DSM、DEM、DOM等数据产品的测量技术,在一些相关专业软件的辅助下,还可以其制作其他数据产品,如三维电子沙盘,生成测区三维景观,可以大大提高水利设计的直观度。     

基于DTM计算并生成三维道路模型

通过综合分析将DTM(Digital Terrain Mode)应用于道路工程的相关研究,提出一种改进的“方向搜索”三角网简化算法;并根据道路的带状特征,建立了边——三角形的拓扑关系;基于Windows平台,利用分治算法和逐点插入算法,采用VC++的MFC和OPENGL语言编程,实现基于DTM计算并生成道路和地形整体三维模型。经测试,证明本文提出的计算理论合理、简单、且执行效率高。     

《结构设计方法》多元化培训方法探讨

《结构设计方法》是一门理论与实紧密结合的设计师培训项目。在该项目实施过程中,我们提出了针对不同内容,采用包括教师理论培训、实验室参观见学、工程专家案例培训、参训者团队研讨等的多元化培训方法(Diversified Training Method,DTM)。论文通过参训者团队的评价,指出DTM有利于参训者多种能力的培养,适合应用于其它工程应用型培训项目中。     

Ecohydraulic modelling of anabranching rivers

In this paper we provide the first quantitative evidence of the spatial complexity of habitat diversity across the flow regime for locally anabranching channels and their potential increased biodiversity value in comparison to managed single‐thread rivers. Ecohydraulic modelling is used to provide evidence for the potential ecological value of anabranching channels. Hydraulic habitat (biotopes) of an anabranched reach of the River Wear at Wolsingham, UK, is compared with an adjacent artificially straightened single‐thread reach downstream. Two‐dimensional hydraulic modelling was undertaken across the flow regime. Simulated depth and velocity data were used to calculate Froude number index, known to be closely associated with biotope type, allowing biotope maps to be produced for each flow simulation using published Froude number limits. The gross morphology of the anabranched reach appears to be controlling flow hydraulics, creating a complex and diverse biotope distribution at low and intermediate flows. This contrasts markedly with the near uniform biotope pattern modelled for the heavily modified single‐thread reach. As discharge increases the pattern of biotopes altered to reflect a generally higher energy system, interestingly however, a number of low energy biotopes were activated through the anabranched reach as new subchannels became inundated and this process creates valuable refugia for macroinvertebrates and fish, during times of flood. In contrast, these low energy areas were not seen in the straightened single‐thread reach. Model results suggest that anabranched channels have a vital role to play in regulating flood energy on river systems and in creating and maintaining hydraulic habitat diversity.