Low-Cost Remote-Sensing Techniques Applied to Drainage Area Studies

The paper describes a project in which colour and infra-red video images were used as the basis for assessing the percentage impermeability of subcatchments for a WALLRUS model. The imagery was obtained from helicopter-mounted video cameras. Computer processes were developed to convert raw data, which were in analogue format, into a format which could be manipulated and displayed by the computer. The computer was able to assess the total permeable and impermeable areas in each subcatchment. These data were used in the WALLRUS model and compared with the results obtained using manually derived data and results from the flow verification survey.     

A high resolution application of a stormwater management model (SWMM) using genetic parameter optimization

Low Impact Development (LID) tools and green infrastructure approaches have been developed and applied to mitigate the urbanization impacts on increasing runoff and pollutant washoff. The present work is the first part of a larger effort to simulate LID scenarios for a large scale urban catchment through up-scaling of high-resolution study catchments using the Stormwater Management Model (SWMM). In this study we present the setup, calibration, validation, and the results of a parameter sensitivity analysis of a high-resolution SWMM model for a highly urbanized small catchment located in Southern Finland. The homogenous subcatchments and associated narrow parameter boundaries, which are allowed by the high spatial resolution, result in insensitivity of SWMM to the fraction of impervious cover. The model optimization, using only the two identified key parameters “depression storage” and “Manning's roughness n for conduit flow”, yielded good performance statistics for both calibration and validation of the model.     

An evaluation of catchment-scale phosphorus mitigation using load apportionment modelling

Functional relationships between phosphorus (P) discharge and concentration mechanisms were explored using a load apportionment model (LAM) developed for use in a freshwater catchment in Ireland with fourteen years of data (1995-2008). The aim of model conceptualisation was to infer changes in point and diffuse sources from catchment P loading during P mitigation, based upon a dataset comprising geospatial and water quality data from a 256 km² lake catchment in an intensively farmed drumlin region of the midlands of Ireland. The model was calibrated using river total P (TP), molybdate reactive P (MRP) and runoff data from seven subcatchments. Temporal and spatial heterogeneity of P sources existed within and between subcatchments; these were attributed to differences in agricultural intensity, soil type and anthropogenically-sourced effluent P loading. Catchment rivers were sensitive to flow regime, which can result in eutrophication of rivers during summer and lake enrichment from frequent flood events. For one sewage impacted river, the LAM estimated that point sourced P contributed up to of 90% of annual MRP load delivered during a hydrological year and in this river point P sources dominated flows up to 92% of days. In the other rivers, despite diffuse P forming a majority of the annual P exports, point sources of P dominated flows for up to 64% of a hydrological year. The calibrated model demonstrated that lower P export rates followed specific P mitigation measures. The LAM estimated up to 80% decreases in point MRP load after enhanced P removal at waste water treatments plants in urban subcatchments and the implementation of septic tank and agricultural bye-laws in rural subcatchments. The LAM approach provides a way to assess the long-term effectiveness of further measures to reduce P loadings in EU (International) River Basin Districts and subcatchments.     

Use of continuous simulation model (COSIMAT) as a complementary tool to model sewer systems: a case study on the Paruck collector,Brussels, Belgium

Episodic Combined Sewer Overflow (CSO) discharges effectively control the ecological status of receiving water bodies. Hydrodynamic models like the Storm Water Management Model (SWMM) are often used to model the CSO events. However, such detailed models are computationally demanding especially when a long‐term simulation of a complex system is required. Considering this, we developed an alternative simple continuous simulation model (COSIMAT) using the SIMULINK? module in MATLAB? as a means of solving the issue of computational time associated with the detailed models. The COSIMAT model was tested against a detailed model set up on the SWMM. The Paruck collector – one of the major Collector of the Brussels’ sewer system was used as an example case. Results showed that the accuracy of the simplified COSIMAT model was comparable to that of the detailed hydrodynamic model (SWMM) with a significant reduction of computational time by a factor of 8. We believe such alternative approaches would be useful to replace a computationally demanding model component of an integrated modelling system of a complex sewer system.     

Climate-change impacts on hydrology and nutrients in a Danish lowland river basin

The Mike 11-TRANS modelling system was applied to the lowland Gjern river basin in Denmark to assess climate-change impacts on hydrology and nitrogen retention processes in watercourses, lakes and riparian wetlands. Nutrient losses from land to surface waters were assessed using statistical models incorporating the effect of changed hydrology. Climate-change was predicted by the ECHAM4/OPYC General Circulation Model (IPCC A2 scenario) dynamically downscaled by the Danish HIRHAM regional climate model (25 km grid) for two time slices: 1961-1990 (control) and 2071-2100 (scenario). HIRHAM predicts an increase in mean annual precipitation of 47 mm (5%) and an increase in mean annual air temperature of 3.2 degrees C (43%). The HIRHAM predictions were used as external forcings to the rainfall-runoff model NAM, which was set up and run for 6 subcatchments within and for the entire, Gjern river basin. Mean annual runoff from the river basin increases 27 mm (7.5%, p<0.05) when comparing the scenario to the control. Larger changes, however, were found regarding the extremes; runoff during the wettest year in the 30-year period increased by 58 mm (12.3%). The seasonal pattern is expected to change with significantly higher runoff during winter. Summer runoff is expected to increase in predominantly groundwater fed streams and decrease in streams with a low base-flow index. The modelled change in the seasonal hydrological pattern is most pronounced in first- or second-order streams draining loamy catchments, which currently have a low base-flow during the summer period. Reductions of 40-70% in summer runoff are predicted for this stream type. A statistical nutrient loss model was developed for simulating the impact of changed hydrology on diffuse nutrient losses (i.e. losses from land to surface waters) and applied to the river basin. The simulated mean annual changes in TN loads in a loamy and a sandy subcatchment were, respectively, +2.3 kg N ha(-1) (8.5%) and +1.6 kg N ha(-1) (6.9%). The rainfall-runoff model and the nutrient loss model were chained with Mike 11-TRANS to simulate the combined effects of climate-change on hydrology, nutrient losses and nitrogen retention processes at the scale of the river basin. The mean annual TN export from the river basin increased from the control to the scenario period by 7.7%. Even though an increase in nitrogen retention in the river system of 4.2% was simulated in the scenario period, an increased in-stream TN export resulted because of the simulated increase in the diffuse TN transfer from the land to the surface-waters.     

Probabilistic model for the annual number of storm overflow discharges in a stormwater drainage system

The paper presents an attempt to develop a probabilistic model for predicting an annual number of storm overflow discharges. Forecasting the occurrence of an overflow discharge event involved the application of the logistic regression, which does not require the development of complex hydrodynamic catchment models. The performed calculations showed that the logistic regression model can be successfully used to evaluate the performance of the emergency overflow weir. The resultant logit model eliminates the necessity to develop hydrodynamic models, to conduct continuous measurements of the flow intensity in the stormwater drainage system and to collect detailed information on the characteristics of the subcatchments within the analyzed catchment. The hydrodynamic model was used to simulate the annual number of discharges. The analysis of the results demonstrated that they are in the range of stochastic values, which indicates an application-related character of the method.     

Impact of climatic fluctuations and land use change on runoff and nutrient losses in rural landscapes

Results on the influence of land use and climatic changes on nutrient losses in the Porijõgi river catchment, south Estonia, are presented. The main tendency in land use changes is a significant increase in abandoned lands (from 1.7% in 1987 to 12.5% in 1994), and a decrease in arable lands (from 41.8 to 22.5%). Significant climatic fluctuations were observed from 1951–1994. Warmer winters (increase from −7.9 to −5.8°C from 1950–1994) and a change in the precipitation pattern have influenced the mean annual water discharge. This results in more intensive material flow during colder seasons and decreased water runoff in summer. Changes in water discharge and land use are also reflected in the mean annual runoff of total inorganic nitrogen (TIN) and total-P which decreased from 15.6 to 2.7 kg N ha⁻¹ yr⁻¹ (83%) and 0.32 to 0.21 kg P ha⁻¹ yr⁻¹ (34%), respectively during this period. However, nutrient losses from the forest subcatchment (upper course) did not change significantly. In contrast, the mean annual runoff of water, organic matter (after biological oxygen demand: BOD₅), TIN, total-P and SO₄ from cultivated subcatchments showed a significant decrease.     

基于产汇流模拟分析的城市居住小区道路系统布局优化策略研究

道路是城市硬质化下垫面的重要组成部分,它既是居住小区雨水径流的主要来源,也是雨水排放的重要通道,因此居住小区中道路系统与雨水产汇流过程关系的探究对于居住小区雨洪韧性的提升具有重要意义。以天津居住小区为例,借助ArcGIS和SWMM,探讨不同降雨强度下分别具有网格型、尽端型以及环网型、环尽型道路布局模式特点的居住小区产汇流规律,并以此为依据提出以雨洪韧性导向为目标的居住小区道路系统布局优化策略。     

Areal rainfall intensity distribution over an urban area and its effect on a combined sewerage system

The application of 21 pluviometers over the whole area of ?ód?, Poland, enabled an examination of areal distribution of intense rainfalls during 2010–2011. On the basis of collected data the distribution of rainfall intensity was analysed and a circular zone model with exponential shape in all directions has been proposed for describing rain storms. Also, the velocity of storm zone movement between 2 and 30 km/h was determined. Using the SWMM 5.0 software, adapted for non-standard use, runoff from three real catchments and combined storm overflow discharge was examined for selected measured rainfalls. An effect of storm zone range and movement was also studied for the same catchments using model storms. It was confirmed that using data from the city pluviometric network enables significantly better simulation results for CSO overflows to be obtained compared to an option based on a single pluviometric station, especially for large catchments greater than 200 hectares.     

Sewerage network modelling in Latvia, use of InfoWorks CS and Storm Water Management Model 5 in Liepaja city

The existing partially combined sewerage system in the city of Liepaja, Latvia, is in a poor structural condition and hydraulic overloading causes flooding and pollution. As part of a wider project to upgrade water services in the city, supported by the European Union (EU) cohesion fund (CF), a mathematical model of the system was constructed and verified. In determining appropriate software for use, two key objectives had to be considered: (i) fast model construction to allow upgrading works to be designed and implemented within the timeframe given in the EU Financing Agreement and (ii) provision of an affordable design and assessment tool for future use by the water company. To meet these objectives, InfoWorks CS software was used for model building and verification and the model was subsequently exported to freely available Storm Water Management Model (SWMM) 5. The predictive results of the two models were compared with validate the SWMM5 model.     

应用结构计算分析软件需注意的几个问题

从正确使用程序、分析判断计算结果、人工调整计算结果等方面,分析了进行结构计算和设计时应用结构计算分析软件时应注意的问题。     

城市污水规划辅助系统中设计流量计算模型的建立

针对GIS平台下污水管网规划中计算管段设计流量存在的问题，在分析城市污水管网结构的基础上，采用递归计算方法建立了设计流量的计算模型，并结合实例编写了递归计算程序，验证了该模型的可行性。     

排水管道泥沙淤积深度估算方法研究

运用C#编程语言实现了SWMM模型参数的自动提取,通过创建BP-人工神经网络实现了节点水深值与模型参数值之间的非线性拟合,基于模型参数率定的思路提出了一种排水管道泥沙淤积深度的估算方法,并且以G市某雨水排水系统为例,采用4场降雨数据对模型进行了校核与验证。结果表明,通过两场降雨数据的验证,对于管径为1.2~1.8 m的管道,淤积深度预测值与实测值之间的绝对误差均在4 cm以内;模拟结果和实测数据的水深峰现时间偏差均低于实测数据历时的5%,峰值的数值偏差均在3%以内;场次3和场次4两场降雨4个监测点的水深预测值与实测值的平均相对误差分别为3.35%、2.98%,2.75%、2.51%,7.39%、6.77%,5.53%、8.15%,说明该方法能够对排水管道淤积情况进行有效预测。     

New high-precision empirical methods for predicting the seepage discharges and free surface locations of earth dams validated by numerical analyses using the IFDM

The interpolation finite difference method (IFDM) can be used in the numerical analysis of steady-state seepage problems over arbitrary domains. In such analyses, by providing the coordinates of change points considering the polygonal domain and boundary conditions, a grid is automatically generated and a numerical solution is promptly obtained. Homogeneous, isotropic dams without tail drains have been investigated in a previous study. However, to consider dams with tail drains, we must alter the previous system slightly. This paper describes the altered system. In earlier times, when computation power was limited and before modern numerical calculation methods had been established, it was highly important for dam engineers to estimate the seepage discharge and the location of the free surface. Several empirical methods were proposed, and these have retained their functionality. For instance, the basic parabola method is an exemplary work that builds on classic empirical methods. In this work, the results obtained using A. Casagrande’s method are compared with those obtained by IFDM, and it is confirmed that there are considerable deviations between them. The so-called “equivalent KZ flow method” is proposed and shown to significantly improve the calculation accuracy for the discharge and free surface location.     

基于GIS构建SWMM城市排水管网模型

基于地理信息系统(GIS)对SWMM城市排水管网模型进行快速构建,并在澳门某小区进行了应用和案例分析.结果表明,该方法简便快速,可准确提取排水管网的空间结构和属性数据,模拟结果与监测数据达到较好的拟合,为模型的进一步深入应用奠定了基础,对其他分布式水文模型的空间结构和属性数据的获取也有一定的借鉴意义.     

River flow and associated transport of sediments and solutes through a highly urbanised catchment, Bradford, West Yorkshire

The hydrological characteristics of catchments become drastically modified in response to urbanisation. The total contributions and dynamics of runoff, suspended sediment and solutes may change significantly and have important implications downstream where they may affect flooding, instream ecological habitat, water quality and siltation of river channels and lakes. Although an appreciation of the likely hydrological changes is crucial for effective catchment management they are still poorly understood. In this paper we present data from a network of river monitoring stations throughout the heavily urbanised Bradford catchment, West Yorkshire. Sites are upstream, within and downstream of the highly urbanised central part of the catchment. Flow, turbidity (calibrated to suspended sediment concentration) and specific conductance (surrogate for solute concentration), logged at 15-min intervals, are presented for a 12-month period (June 2000 to June 2001). The total amounts and dynamics of flow, solute and suspended sediment transport were investigated. Estimated total flow and suspended sediment transport for the monitoring period were found to be high in response to the high total rainfall. Flow and sediment transport regimes were extremely 'flashy' throughout the catchment and became increasingly flashy in a downstream direction. Suspended sediment discharged from the Bradford subcatchment makes an important contribution to downstream sediment transport on the river Aire at Beal. Data suggest that the urbanised part of the Bradford catchment is extremely important in contributing solutes to the Beck (river). Although flow and sediment are also contributed to the Bradford Beck in the urbanised part of the catchment the data suggest that significant amounts may enter the combined sewer system and bypass the river. Understanding the spatial and temporal variations of flow and the transport of suspended sediment and solutes in rivers in urbanized subcatchments is crucial to their effective management and monitoring. Furthermore, this knowledge may be extremely important to the management and monitoring of downstream rivers in large scale mixed catchments.     

swmmr - an R package to interface SWMM

ABSTRACT

The stormwater management model SWMM of the US EPA is widely used to analyse, design or optimise urban drainage systems. To perform advanced analysis and visualisations of model data this technical note introduces the R package swmmr. It contains functions to read and write SWMM files, initiate simulations from the R console and to convert SWMM model files to and from GIS data. Additionally, model data can be transformed to produce high quality visualisations. In accordance with SWMM’s open source policy the package can be obtained through github.com or the Comprehensive R Archive Network (CRAN).     

Combining an Angle Criterion with Voxelization and the Flying Voxel Method in Reconstructing Building Models from LiDAR Data

Abstract: Traditional documentation capabilities of laser scanning technology can be further exploited for urban modeling through the transformation of resulting point clouds into solid models compatible for computational analysis. This article introduces such a technique through the combination of an angle criterion and voxelization. As part of that, a k‐nearest neighbor (kNN) searching algorithm is implemented using a predefined number of kNN points combined with a maximum radius of the neighborhood, something not previously implemented. From this sample, points are categorized as boundary or interior points based on an angle criterion. Façade features are determined based on underlying vertical and horizontal grid voxels of the feature boundaries by a grid clustering technique. The complete building model involving all full voxels is generated by employing the Flying Voxel method to relabel voxels that are inside openings or outside the façade as empty voxels. Experimental results on three different buildings, using four distinct sampling densities showed successful detection of all openings, reconstruction of all building façades, and automatic filling of all improper holes. The maximum nodal displacement divergence was 1.6% compared to manually generated meshes from measured drawings. This fully automated approach rivals processing times of other techniques with the distinct advantage of extracting more boundary points, especially in less dense data sets (<175 points/m²), which may enable its more rapid exploitation of aerial laser scanning data and ultimately preclude needing a priori knowledge.     

基于SWMM模拟上海市区排水及地面淹水过程

针对上海市城区排水系统的水文水力学特性，以SWMM（Storm Water Management Model）为基础开发出适合上海市区产流及排水特点和防汛管理要求的城市雨洪模型。模拟结果表明，该模型的计算结果较为理想、可靠，可在实时和规划条件下动态模拟各排水片和街区的地面积水全过程，并能满足市区防汛预报、水情分析、工程规划与管理等工作的要求。该模型对其他城市的类似工作具有较好的参考价值和指导意义。     

Characteristics of wet and dry weather heavy metal discharges in the Yeongsan Watershed, Korea

A comprehensive water quality monitoring program was conducted in the Yeongsan (YS) River, Korea from 2005 to present to investigate wet and dry weather pollutant discharge in an attempt to establish point and non-point pollution management strategies. As part of this monitoring program, 11 heavy metal species were measured during dry and wet weather conditions in the YS River, where Gwangju City (GJ), a subcatchment of the YS River, was further monitored to clarify the responsibility of different metal species discharged into the mainstream. Monthly grab water samples showed that greater amounts of metals along the YS River were discharged during the wet summer months due largely to storm runoff. In addition, further monitoring results revealed that GJ, a highly urbanized area, was a significant contributor of the heavy metals being discharged into the YS River during both wet and dry weather. The most abundant metal species discharged from GJ were manganese, aluminum and iron with different contributions of wet and dry weather flows to the total discharge load. Wet weather flow was a significant contributor to the annual dissolved metal loads, accounting for 44-93% of the annual load depending on the metal species, with the exception of chromium and cadmium (9% and 27%, respectively). Mostly, metal loads during wet weather were shown to be proportional to the rainfall depth and antecedent dry period. A substantial fraction of metals were also associated with solids, suggesting that sedimentation might be an appropriate management practice for reducing the metal load generated in GJ. Overall, although dissolved metal concentrations in YS River were at an acceptable level for aquatic community protection, continual metal discharge throughout the year was considered to be a potential problem in the long-term due to gradual water quality degradation as well as continuous metal accumulation in the system.