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1.
Local characteristics of drainage networks such as cross-section geometry and hydraulic roughness coefficient, influence surface
water transfers and must be taken into account when assessing the impact of human activities on hydrological risks. However,
as these characteristics have not been available till now through remote sensing or hydrological modelling, the only available
methods are interpolation or simulation based on scarce data. In this paper we propose a statistical model based on geostatistics
that allows us to take account of both the spatial distribution and spatial uncertainties. To do this, we modify the geostatistical
framework to suit directed tree supports corresponding to drainage network structures. The stationarity concept is specified
assuming conditional independence between parts of the network; variogram fitting and modelling are then modified accordingly.
A sequential multi Gaussian simulation procedure going upstream along the network is proposed. We illustrate this approach
by studying the width of an 11-km long artificial drainage network in the south of France. 相似文献
2.
Normally, decision makers use number of pipe broken in specific sections of water distribution systems to determine the pipes to be replaced. This index cannot solely evaluate hydraulic and quality parameters of the system and effects of pipe renovation on the system performance. In this study, a methodology is presented to manage the rehabilitation and replacement of water distribution network using hydraulic and geospatial information systems models. A preprocessor subroutine is developed to link geospatial information systems and hydraulic software. Hydraulic parameters together with the attribute data of pipes are used to determine the required renovation schemes based on several criteria. The proposed indices consist of pipe breaks and leakage analyses, hydraulic and quality performance and mechanical reliability of the network. A novel approach is also introduced to calculate leakage values throughout the network. Results of a real case study by the developed model introduced replacement of 4 km 40 mm galvanized pipes instead of 11 km 100 mm asbestos-cement pipes from conventional method. It is observed that the suggested geographic information system based model produces more realistic results with less cost for renovation schemes in comparison with conventional method which just consider number of bursts as a key criterion. 相似文献
3.
数字高程模型(DEM)在流域水文模型中得到了广泛应用,主要是因为DEM能够自动提取流域水文模型所需要的确定流域排水结构的水文信息。回顾并讨论了DEM在流域水文模型应用中的几个问题,主要包括河网自动提取的方法、DEM中排水方向的确定以及封闭洼地的处理,同时还包括在流域水文模型中应用时DEM的结构类型及尺度问题。由于由DEM生成的模拟河网与流域实际河网间存在一定的差别,最后还讨论了如何对模拟河网进行矫正的问题。 相似文献
4.
Groundwater inflow assessment is essential for the design of tunnel drainage systems, as well as for assessment of the environmental impact of the associated drainage. Analytical and empirical methods used in current engineering practice do not adequately account for the effect of the jointed-rock-mass anisotropy and heterogeneity. The impact of geo-structural anisotropy of fractured rocks on tunnel inflows is addressed and the limitations of analytical solutions assuming isotropic hydraulic conductivity are discussed. In particular, the study develops an empirical correction to the analytical formula frequently used to predict groundwater tunnel inflow. In order to obtain this, a discrete network flow modelling study was carried out. Numerical simulation results provided a dataset useful for the calibration of some empirical coefficient to correct the well-known Goodman’s equation. This correction accounts for geo-structural parameters of the rock masses such as joint orientation, aperture, spacing and persistence. The obtained empirical equation was then applied to a medium-depth open tunnel in Bergamo District, northern Italy. The results, compared with the monitoring data, showed that the traditional analytical equations give the highest overestimation where the hydraulic conductivity shows great anisotropy. On the other hand, the empirical relation allows a better estimation of the tunnel inflow. 相似文献
5.
Prolonged and high intensity rainfall often saturates urban drainage systems and generates urban pluvial flooding, resulting in hazardous flash floods. The city most affected by urban flooding in Colombia (South America) is Barranquilla since lacks a proper storm water drainage system. Heavy rainfall produces flash floods to quickly become torrential streams that flow down the streets endangering pedestrians. This research describes a low-cost early warning system (EWS) to detect in real time the hazard level of a stream in an ungauged basin. The EWS indicates whether it is safe or not for pedestrians to cross a flooded street, based on certain criteria used to assess the hazard level of the torrent. A hydrological and hydraulic model calculates the flow, velocity and water level in all cross sections along the stream. The model uses only real-time measurements of rain gauges and topographic survey data to determine the hazard level. Finally, a wireless sensor network sends the alert to a web platform and warns the community in real time. 相似文献
6.
An innovative approach in the investigation of complex landscapes for hydraulic modelling applications is the use of terrestrial laser scanner (TLS) that can lead to a high-resolution digital elevation model (DEM). Another notable factor in flood modelling is the selection of the hydrodynamic model (1D, 2D and 1D/2D), especially in complex riverine topographies, that can influence the accuracy of flood inundation area and mapping. This paper uses different types of hydraulic–hydrodynamic modelling approaches and several types of river and riparian area spatial resolution for the implementation of a sensitivity analysis for floodplain mapping and flood inundation modelling process at ungauged watersheds. Four data sets have been used for the construction of the river and riparian areas: processed and unprocessed TLS data, topographic land survey data and typical digitized contours from 1:5000-scale topographic maps. Modelling approaches combinations consist of: one-dimensional hydraulic models (HEC-RAS, MIKE 11), two-dimensional hydraulic models (MIKE 21, MIKE 21 FM) and combinations of coupled hydraulic models (MIKE 11/MIKE 21) within the MIKE FLOOD platform. Historical flood records and estimated flooded area derived from an observed extreme flash-flood event have been used in the validation process using 2 × 2 contingency tables. Flood inundation maps have been generated for each modelling approach and landscape configuration at the lower part of Xerias River reach at Volos, Greece, and compared for assessing the sensitivity of input data and model structure uncertainty. Results provided from contingency table analysis indicate the sensitivity of floodplain modelling on the DEM spatial resolution and the hydraulic modelling approach. 相似文献
7.
以往水系的勾绘、采样点位的布设工作均由人工在地形底图上手工完成,工作量大,且影响化探工作进度。通过规则网格的数字高程模型生成水系网,实现了精确度较高的水系网提取算法。该算法先按照水系级别和水系长度进行样点初布,然后检测样点的数量及密度是否达到要求,再根据布样要求进行样点的补充与修改,据此研究水系沉积物采样自动化布置方法,实现基于等高线的水系沉积物采样点的自动布设,提高了化探采样工作效率。 相似文献
8.
Septic systems located near coastal waterways can contribute to nutrients that lead to eutrophication, harmful algal blooms, and high levels of fecal coliforms such as E. coli. This study defines pathways and timescales of nitrogen transport released from septic systems using a groundwater-flow and nitrogen transport model of a coastal subdivision connected to 2,000 septic systems and dissected by a dense network of canals. Lift station effluent data are used as a proxy to quantify average household septic nitrogen and fluid contributions of 11 kg/year and 160 m3/year, respectively. These fluxes are upscaled and applied to five sewer conversion zones, each having a known number of septic systems. Model results provide a basis for assessing nitrogen transport timescales associated with (1) coastal groundwaters for regions with high septic density near the coastline and (2) groundwater–canal interaction. Timescales associated with nitrogen removal by natural groundwater flow in a sandy surficial aquifer, following septic to sewer conversion, are predicted by the model to be on the order of 2–3 years for 50% reduction and 8–10 years for 90% reduction. Both numerical and collected field data indicate that canals significantly influence groundwater flow and have the potential to convey nitrogen to coastal waters at rates several orders of magnitude higher than introduced by submarine discharge along the coast. Pre and post sewer conversion data on nitrate and total nitrogen in shallow groundwater from a nearby field site, obtained post-model development, support the nitrogen concentrations and timescales predicted by the numerical model. 相似文献
9.
基于辽河水系老哈河流域栅格DEM数据,分别采用数字高程流域水系模型(DEDNM)、河流工具RiverTools、地理信息系统Arcview软件,根据地形提取水系信息,构建数字流域,并分析比较了三者在凹陷区域识别、水系、子流域及其拓扑关系生成方面的差异。总的来说,数字高程流域水系模型的可修改性较好;而RiverTools软件可视化程度高,使用方便,并具备强大的图示和地形分析功能;Arcview基于地理信息系统(GIS)更易于进行二次开发。 相似文献
10.
An area-differentiated model approach (MEPhos) for the quantification of mean annual P-inputs from point and diffuse sources
is presented. The following pathways are considered: artificial drainage, wash-off, groundwater outflow, soil erosion, rainwater
sewers, combined sewer overflows, municipal waste water treatment plants and industrial effluents. Two retention functions
for rivers and reservoirs are included in order to model P-sinks within a river basin. This allows a complete record of P-loads
in heterogeneous meso- and macroscale river basins and enables validation of modeling results with water quality data on a
load basis. The model is applied to the River Ruhr basin (4,485 km 2) in Germany, which includes contrasting natural conditions, land use patterns as well as population and industry densities.
Based on validated modelling results sub-areas of high P-loads are localized and management options for the reduction of P-inputs
to surface waters are proposed taking into account the site conditions of the sub-areas relevant for high P-inputs into surface
waters. 相似文献
11.
Urban pluvial flash floods have become a matter of widespread concern, as they severely impact people’s lives in urban areas. Hydrological and hydraulic models have been widely used for urban flood management and urban planning. Traditionally, to reduce the complexity of urban flood modelling and simulations, simplification or generalization methods have been used; for example, some models focus on the simulation of overland water flow, and some models focus on the simulation of the water flow in sewer systems. However, the water flow of urban floods includes both overland flow and sewer system flow. The overland flow processes are impacted by many different geographical features in what is an extremely spatially heterogeneous environment. Therefore, this article is based on two widely used models (SWMM and ANUGA) that are coupled to develop a bi-directional method of simulating water flow processes in urban areas. The open source overland flow model uses the unstructured triangular as the spatial discretization scheme. The unstructured triangular-based hydraulic model can be better used to capture the spatial heterogeneity of the urban surfaces. So, the unstructured triangular-based model is an essential condition for heterogeneous feature-based urban flood simulation. The experiments indicate that the proposed coupled model in this article can accurately depict surface waterlogged areas and that the heterogeneous feature-based urban flood model can be used to determine different types of urban flow processes. 相似文献
12.
Fracture network modelling plays an important role in many application areas in which the behaviour of a rock mass is of interest. These areas include mining, civil, petroleum, water and environmental engineering and geothermal systems modelling. The aim is to model the fractured rock to assess fluid flow or the stability of rock blocks. One important step in fracture network modelling is to estimate the number of fractures and the properties of individual fractures such as their size and orientation. Due to the lack of data and the complexity of the problem, there are significant uncertainties associated with fracture network modelling in practice. Our primary interest is the modelling of fracture networks in geothermal systems and, in this paper, we propose a general stochastic approach to fracture network modelling for this application. We focus on using the seismic point cloud detected during the fracture stimulation of a hot dry rock reservoir to create an enhanced geothermal system; these seismic points are the conditioning data in the modelling process. The seismic points can be used to estimate the geographical extent of the reservoir, the amount of fracturing and the detailed geometries of fractures within the reservoir. The objective is to determine a fracture model from the conditioning data by minimizing the sum of the distances of the points from the fitted fracture model. Fractures are represented as line segments connecting two points in two-dimensional applications or as ellipses in three-dimensional (3D) cases. The novelty of our model is twofold: (1) it comprises a comprehensive fracture modification scheme based on simulated annealing and (2) it introduces new spatial approaches, a goodness-of-fit measure for the fitted fracture model, a measure for fracture similarity and a clustering technique for proposing a locally optimal solution for fracture parameters. We use a simulated dataset to demonstrate the application of the proposed approach followed by a real 3D case study of the Habanero reservoir in the Cooper Basin, Australia. 相似文献
13.
Earth System Science (ESS) observational data are often inadequately semantically enriched by geo-observational information systems to capture the true meaning of the associated data sets. Data models underpinning these information systems are often too rigid in their data representation to allow for the ever-changing and evolving nature of ESS domain concepts. This impoverished approach to observational data representation reduces the ability of multi-disciplinary practitioners to share information in a computable way. Object oriented techniques that are typically employed to model data in a complex domain (with evolving domain concepts) can unnecessarily exclude domain specialists from the design process, invariably leading to a mismatch between the needs of the domain specialists, and how the concepts are modelled. In many cases, an over simplification of the domain concept is captured by the computer scientist. This paper proposes that two-level modelling methodologies developed by health informaticians to tackle problems of domain specific use-case knowledge modelling can be re-used within ESS informatics. A translational approach to enable a two-level modelling process within geo-observational sensor systems design is described. We show how the Open Geospatial Consortium’s (OGC) Observations & Measurements (O&M) standard can act as a pragmatic solution for a stable reference-model (necessary for two-level modelling), and upon which more volatile domain specific concepts can be defined and managed using archetypes. A rudimentary use-case is presented, followed by a worked example showing the implementation methodology and considerations leading to an O&M based, two-level modelling design approach, to realise semantically rich and interoperable Earth System Science based geo-observational sensor systems. 相似文献
15.
In cities, the existence of impervious structures, such as road pavements, parking lots, footpaths, sidewalks, and roofs, can limit the magnitude of rainfall infiltration greatly. Stormwater run-off in storm sewer often dominates, which can cause problems of urban flooding easily during heave rainfalls. In rain and sewage diversion, perforated storm sewer is proposed to enable the occurrence of stormwater infiltration into the ground, which can change the prolonged drought-like condition. Model-scale laboratory tests are conducted to assess the infiltration process of water through drainage holes around the sewer circumference. The experimental data are also used to calibrate a numerical model, after which numerical parametric analysis is carried out. It is found that the feature of drainage holes only influences the wetting front in the initial stage of infiltration. In the end, the egg-shaped contour of wetting front with greater influencing zone below the sewer is obtained. The cumulative infiltration with time can be described by an infiltration model, which is positively correlated with the diameter and the number of drainage holes. The optimal opening ratio is recommended as 0.25%, which can provide the most effective drainage capacity. 相似文献
16.
Green infrastructure (GI)-based approaches to urban drainage such as sustainable urban drainage systems (SUDS) could provide Sub-Saharan cities with an opportunity to address projected climate change impacts and existing deficits in their drainage infrastructure, even more so due to the synergies between an enhanced green infrastructure stock and sustainable urban development. The objective of this paper was to assess the theoretical value of using green infrastructure for stormwater management as an alternative and supplement to conventional pipe-based stormwater management systems. A SWOT analysis is performed to assess the potential that SUDS hold if adopted and implemented in Sub-Saharan cities. This analysis is based on a review of sustainable stormwater management as well as urban planning and governance literature. Results show that despite seemingly significant barriers to the adoption of SUDS in Sub-Saharan cities such as low prioritization on the urban agenda and lack of data among others, the concept may hold valuable potential for flood risk reduction, even more so due to its multi-functionality and synergies with urban agriculture, amenity and water supply. In the light of the existing threats and weaknesses, it is recommended that GI-based SUDS may be best approached initially as experiments at a local community scale. 相似文献
17.
Ideas about the character and evolution of englacial drainage systems have been deeply influenced by the theoretical model developed by Shreve [1972. Movement of water in glaciers. Journal of Glaciology 11(62), 205–214]. The Shreve model is based on three main assumptions: (1) englacial drainage is in steady state; (2) englacial water will flow along the steepest hydraulic gradient within the glacier; and (3) pressure head equals the pressure of the surrounding ice minus a small component due to melting of the walls. The Shreve model has been widely adopted as a fundamental component of englacial drainage theory. There is no evidence, however, that the model provides a realistic picture of actual glacial drainage systems.To evaluate Shreve's theory, we used speleological techniques to directly survey englacial conduits. We mapped a total of 8.25 km of passage in 27 distinct englacial conduits in temperate, polythermal, cold-based and debris-covered glaciers between 2005 and 2008. New information reported here is supplemented by published data on 40 other englacial conduits located worldwide and surveyed to ice depths of 176 m using speleological techniques. In all cases, englacial drainage systems consisted of a single unbranching conduit. Englacial conduit morphologies were found to be intimately linked to the orientation of a glacier's principal stresses or the presence of pre-existing lines of high hydraulic conductivity. If a sufficient supply of water is available, hydrofracturing forms vertical conduits in zones of longitudinal extension and subhorizontal conduits where longitudinal stresses are compressive. On unfractured glacier surfaces, relatively shallow subhorizontal conduits with migrating nickpoints form by cut-and-closure provided channel incision is significantly faster than surface lowering. Conduits can also form along permeable debris-filled crevasse traces that connect supraglacial lake basins of different potential. Our results suggest that Shreve-type englacial drainage systems do not exist and implies that englacial conduits can only penetrate through thick ice to recharge the bed where supraglacial water bodies either intersect, or are advected through, zones of acceleration. 相似文献
19.
三峡区间的数字流域水系模型采用基于格网型的数字高程模型坡面流模拟方法和处理"洼地"的最短流程法构建,并以新安江模型为基础建立具有诸多特点的三峡区间流域水文模型;以水动力学理论为基础建立考虑水利工程影响的河川型水库洪水演进模型,并实现这两者的有机耦合。在GIS平台上,将三峡区间流域水文模型、库区洪水演进模型和流域水系生成模型在底层集成,研制了功能先进和完善的三峡水库实时洪水预报系统。该系统已安装在三峡总公司梯级水库调度中心,投入试运行。 相似文献
20.
选取资水流域新宁水文站以上集水面积为研究区域,基于空间分辨率为30s的数字高程模型数据构建数字流域水系,运用新安江模型和NAM模型分别对新宁站的日径流过程进行模拟。采用确定性系数和信息熵对两个模型的模拟结果进行比较分析。在信息熵计算过程中,以实测流量为标准序列,计算两种日模型模拟结果与实测序列残差,然后进行归一化,计算潜在信息测度和信息熵相对测度。信息熵越大表明流量计算序列与实测序列过程线在垂向上相似性强,但这并不代表确定性系数大、径流深相对误差小。 相似文献
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