Channel Flow Routing Research Articles

Establishing a time‐varying flood‐wave impulse function combined with a dynamic machine‐learning technique in response to the disturbance of boundary conditions

AbstractTo seek other alternative approaches besides numerical methods, the linearized Saint Venant equations were utilized to derive the channel response functions for simulating streamflow. This study advocates developing a new approach to make the temporal distribution of response functions more flexible by introducing time‐varying reference parameters which depend on both the upstream inflow and the downstream boundary conditions. Moreover, to expand the model applicability in natural channels with irregular cross‐sectional shapes affected by the unsteady inflow, lateral flow, and the variation of tide level, a dynamic neural network algorithm is jointly applied to determine more appropriate time‐varying hydraulic parameters which are adopted in the channel flow response functions respectively derived from upstream and downstream boundary conditions. The tidal level at the estuary and the upstream inflow discharge are simultaneously considered influential factors to determine an optimal set of reference parameters by applying a machine learning technique, and this prediction can further be provided for updating the channel response functions. The novelty of this study is to propose a complete methodology to combine channel response functions with the machine learning algorithm for ameliorating the accuracy of channel flow simulation and resolving the uncertainty of model parameters. Therefore, by using the proposed method, not only the physical mechanism of Saint Venant equations can be preserved, but also the optimal hydraulic parameters can be specified. The problem of numerical instability during channel flow routing can be eliminated by using the proposed new model and therefore the reliability of real‐time flood forecasting can be reinforced.

An automatic partition-based parallel algorithm for grid-based distributed hydrological models

Parallel computing is a primary way to increase computing efficiency of grid-based distributed hydrological models. This study proposed an automatic partition-based parallel algorithm (APPA) to approach the theoretical maximum speedup ratio (TMSR). Through a combination of flexible partition for the domain decomposition and the load balance of parallel simulation, APPA optimizes the parallelization of hillslope and channel flow routing processes at sub-basin and channel unit level, respectively. To illustrate APPA's performance, we embedded it in a distributed ecohydrological model, and then applied the updated model to three watersheds at different spatial scales. The results indicate that APPA effectively promoted parallel performance. The estimated speedup ratio approached 93–97% of the TMSR for simulating hillslope processes and 91–98% of the TMSR for simulating channel processes using 26-threads in all three watersheds. These improvements justify that APPA is effective in accelerating model simulation and thus benefits future model-based research.

Continental Scale Heterogeneous Channel Flow Routing Strategy for Operational Forecasting Models

AbstractThe benefits of operational forecasting models to the general public are numerous. They support water management decisions, provide the opportunity to mitigate the impacts of weather‐ and flood‐related disasters and potentially save lives and properties. Channel flow routing is a key component of these models and affects their ability to forecast flood depth, duration, and extent. Continental scale channel flow routing within the operational forecasting environments encounters a broad spectrum of hydraulic characteristics. Deploying computationally demanding approaches, such as the dynamic wave, should be limited in time and space to conditions where the inertia terms are significant (typically in low‐gradient environments and whenever backwater effects are prominent); otherwise, efficient and robust methods, e.g., Kinematic, Muskingum‐Cunge or diffusive waves should be the default. The heterogeneous routing approach presented here provides a framework to evaluate the balance between friction, inertia, and pressure and strategically triggers the appropriate wave approximation. The strategy recommended here is to activate the appropriate wave approximation based on the ambient hydraulic conditions, and smoothly transitions among these approximations. This strategy, if successfully implemented, would strike a balance among the performance metrics of operational forecasting models, namely, computational efficiency, accuracy, and minimization of computational instabilities.

On Dam-Break Flow Routing in Confluent Channels.

The flood propagation at a confluence of channels exhibits a unique routing pattern, while there are few studies on the routing of dam-break flow in confluent channels. In this study, we conducted physical experiments and a numerical simulation to investigate the influence of different confluence angles on the routing of a dam-break flood. Experiments were carried out in smooth, transparent, rectangular prismatic channels to study the dam-break flow under four different confluence angles. The flow velocity was measured using an image processing technique, and the surface flow field was effectively captured by synchronously recording the particle motion images. Based on the variation of the water level and flow discharge, as the confluence angle increased, the retardation and abatement effects on the flood increased. Specifically, the flood arrival time was delayed by approximately 0.91% to 21.18%, and the peak flood discharge was reduced by approximately 9.05% to 58.36%. Combined with the surface flow field at the confluence and in the downstream sections, as the confluence angle increased, the impact points at the confluence and in the downstream straight sections moved upward, and the impact range was reduced. Combined with the pressure variation pattern, the routing of dam-break flow in the confluent channels experienced a process of impact-reflection-return-attenuation.

Discussion of “Application of Genetic Programming to Flow Routing in Simple and Compound Channels” by Elahe Fallah-Mehdipour, Omid Bozorg-Haddad, Hossein Orouji, and Miguel A. Mariño

Discussion of “Application of Genetic Programming to Flow Routing in Simple and Compound Channels” by Elahe Fallah-Mehdipour, Omid Bozorg-Haddad, Hossein Orouji, and Miguel A. Mariño

Closure to “Application of Genetic Programming to Flow Routing in Simple and Compound Channels” by Elahe Fallah-Mehdipour, Omid Bozorg-Haddad, Hossein Orouji, and Miguel A. Mariño

Closure to “Application of Genetic Programming to Flow Routing in Simple and Compound Channels” by Elahe Fallah-Mehdipour, Omid Bozorg-Haddad, Hossein Orouji, and Miguel A. Mariño

Verification of Saint-Venant equations solution based on the lax diffusive method for flow routing in natural channels

RESUMO Modelos hidrodinâmicos, formados pelas equações de Saint-Venant, representam o escoamento transitório em sistemas hídricos, e simulam a propagação de vazões ao longo do tempo e do espaço. Diversas soluções numéricas têm sido aplicadas a essas expressões, porém frequentemente são encontradas diferenças de resultados entre procedimentos, uma vez que toda aproximação numérica possui limitações. Canais naturais são caracterizados por um comportamento dinâmico das vazões, considerando os usos múltiplos da água e as alterações de morfologia, que ocorrem naturalmente ou por influência antrópica. Nesse contexto, esse trabalho procura complementar o entendimento acerca de diferentes hipóteses e aproximações para solução das equações de Saint-Venant, verificando resultados do esquema difusivo de Lax e comparando com o software HEC-RAS. O estudo de caso consiste em um rio que drena uma área densamente povoada (rio Iguaçu, localizado em Curitiba-PR). Ao comparar os hidrogramas observados e simulados, foi possível avaliar que a forma como as equações são resolvidas, que por sua vez determina o tipo de condição de contorno a ser utilizada, pode contribuir para diferenças na vazão simulada. Adicionalmente, foi observado que a calibração alcançada é adequada, assim como a hipótese de seção transversal trapezoidal. O desenvolvimento da pesquisa deve auxiliar ainda o avanço na solução do modelo hidrodinâmico pelo esquema difusivo de Lax, principalmente no que concerne à eficiência computacional. Esquemas explícitos, apesar de serem mais sensíveis ao intervalo temporal de simulação, apresentam a vantagem de simplificação para implementação, o que pode trazer benefícios no estudo de sistemas complexos, como rios urbanos.

Real-time updating of HEC-RAS model for streamflow forecasting using an optimization algorithm

ABSTRACT Real-time updating of channel flow routing models is essential for error reduction in hydrological forecasting. Recent updating techniques found in scientific literature, although very promising, are complex and often applied in models that demand much time and expert knowledge for their development, posing challenges for using in an operational context. Since powerful and well-known computational tools are currently available, which provide easy-to-use and less time-consuming platforms for preparation of hydrodynamic models, it becomes interesting to develop updating techniques adaptable to such tools, taking full advantage of previously calibrated models as well as the experience of the users. In this work, we present a real-time updating procedure for streamflow forecasting in HEC-RAS model, using the Shuffled Complex Evolution - University of Arizona (SCE-UA) optimization algorithm. The procedure consists in a simultaneous correction of boundary conditions and model parameters through: (i) generation of a lateral inflow, based on Soil Conservation Service (SCS) dimensionless unit hydrograph and; (ii) estimation of Manning roughness in the river channel. The algorithm works in an optimization window in order to minimize an objective function, given by the weighted sum of squared errors between simulated and observed flows where differences in later intervals (start of forecast) are more penalized. As a case study, the procedure was applied in a river reach between Salto Caxias dam and Hotel Cataratas stream gauge, located in the Lower Iguazu Basin. Results showed that, with a small population of candidate solutions in the optimization algorithm, it is possible to efficiently improve the model performance for streamflow forecasting and reduce negative effects caused by lag errors in simulation. An advantage of the developed procedure is the reduction of both excessive handling of external files and manual adjustments of HEC-RAS model, which is important when operational decisions must be taken in relatively short times.

Application of Genetic Programming to Flow Routing in Simple and Compound Channels

AbstractHydraulic methods can model channel flow with high accuracy using data related to channel geometry and flow regime that render the computational effort burdensome. In contrast, hydrologic methods apply simplifying assumptions in their algorithms for flow routing. This paper implements genetic programming (GP) to calculate hydrographs in simple and compound channels. Predicted hydrographs for the simple and compound channels are compared with those predicted by a Muskingum model and a one-dimensional (1D) coupled characteristic-dissipative-Galerkin (CCDG-1D) procedure. Results show that the differences between predicted hydrographs by GP and modeled hydrographs by the Muskingum and CCDG-1D methods are similar in simple and compound channels. Moreover, GP yields acceptable predicted hydrographs with decreased computational burden. These results indicate that the proposed GP method is effective in the prediction of open-channel flow.

A joint power control, time-sharing and routing scheme to minimize spectrum utilization in wireless mesh networks

Despite the abundance of the optimization models proposed so far in the literature to improve the performance or to reduce the deployment costs of wireless mesh networks, only a few works have addressed explicitly the minimization of spectrum utilization in these networks. Considering the scarcity of this critical resource mainly caused by the tremendous recent developments in wireless technologies, we address in this paper the problem of minimizing the number of used radio channels while satisfying a set of end-to-end traffic demands. We formulate to this end a mixed-integer linear program as a cross-layer optimization approach acting on various aspects, such as channel assignment, power control, medium access and flow routing. Due to the expensive computational costs required to find exact solutions, we propose various approximation schemes that provide near-optimal results in a reasonable amount of time. We illustrate the impact of various parameters such as radio patterns, requested traffic loads, network density on the total required spectrum. Results show how a knowledgeable exploitation of spatial reuse can save significantly spectrum utilization.

A layered approach to parallel computing for spatially distributed hydrological modeling

Distributed hydrological simulations over large watersheds usually require an extensive amount of computation, which necessitates the use of parallel computing. Each type of hydrological model has its own computational characteristics and therefore needs a distinct parallel-computing strategy. In this paper, we focus on one type of hydrological model in which both overland flow routing and channel flow routing are performed sequentially from upstream simulation units to downstream simulation units (referred to as Fully Sequential Dependent Hydrological Models, or FSDHM). There has been little published work on parallel computing for this type of model. In this paper, a layered approach to parallel computing is proposed. This approach divides simulation units into layers according to flow direction. In each layer, there are no upstream or downstream relationships among simulation units. Thus, the calculations on simulation units in the same layer are independent and can be conducted in parallel. A grid-based FSDHM was parallelized with the Open Multi-Processing (OpenMP) library to illustrate the implementation of the proposed approach. Experiments on the performance of this parallel model were conducted on a computer with multi-core Central Processing Units (CPUs) using datasets of different resolutions (30 m, 90 m and 270 m, respectively). The results showed that the parallel performance was higher for simulations with large datasets than with small datasets and the maximum speedup ratio reached 12.49 under 24 threads for the 30 m dataset.

Runoff simulation using distributed hydrological modeling approach, remote sensing and GIS techniques: A case study from an Indian agricultural watershed

Abstract. Distributed hydrological modeling has the capability of simulating distributed watershed basin processes, by dividing a heterogeneous and complex land surface divided into computational elements such as Hydrologic Response Units (HRU), grid cell or sub watersheds. The present study was taken up to simulate spatial hydrological processes from a case study area of Kansavati watershed in Purulia district of West Bengal, India having diverse geographical features using distributed hydrological modelling approach. In the present study, overland flow in terms of direct runoff from storm rainfall was computed using USDA Soil Conservation Services (SCS) curve number technique and subsequently it served as input to channel routing model. For channel flow routing, Muskingum-Cunge flood routing technique was used, specifically to route surface runoff from the different sub watershed outlet points to the outlet point of the watershed. Model parameters were derived for each grid cell either from remote sensing data or conventional maps under GIS environment. For distributed approach, validation show reasonable fit between the simulated and measured data and CMR value in all the cases is negative and ranges from -0.1 to - 0.3. Further, this study investigates the effect of cell size on runoff simulation for different grid cell sizes of 23, 46, 92, 184, 368, 736, 1472 m resolution. The difference between simulated and observed runoff values increases with the increase of grid size beyond 184 m more prominently. Further, this model can be used to evaluate futuristic water availability scenarios for an agricultural watershed in eastern India.

Reverse flow routing in open channels: A Bayesian Geostatistical Approach

Summary Reverse flow routing in open channels is a procedure of practical interest: it allows to obtain hydrographs in upstream ungauged stations by means of information available at downstream monitored sites. In this paper a Bayesian Geostatistical Approach for reverse flow routing in open channels is presented. The capabilities of the methodology are shown by means of synthetic test cases. Input hydrographs of different shape were routed downstream using a numerical flow model that solves the one dimensional De Saint Venant equations; the resulting outflow hydrographs were, in almost all the cases, corrupted with random errors and then used for the inversion. Both prismatic and non-prismatic irregular channels, under subcritical flow conditions, were analyzed as well. The considered non-prismatic channel with irregular cross sections and variable friction coefficients represents a very practical situation that can be encountered in the field. The results show that the proposed methodology is able to properly reproduce the input inflows even in presence of errors affecting the downstream discharges up to 10%.

Hydrologic procedures of storm event watershed models: a comprehensive review and comparison

Currently, many watershed models are available that have various complexities, strengths, and weaknesses. The basic mathematical foundations of these mathematical models are often overlooked due to high demands on convenient applications with graphical user interfaces. Although this and other factors are important while selecting a model, the mathematical foundation should also be taken into account, as performance or efficiency and accuracy of a model depend on its simplicity or complexity. A comprehensive review of 14 storm event watershed models was conducted. Hydrologic procedures (rainfall excess, flow routing, and subsurface flow) of the models are presented and compiled. Among the procedures, flow routing has the most influence on model performances (speed and accuracy). Overland and channel flow routing procedures using different flow-governing equations, having various approximations and solved by different methods, are compared based on their relative levels of physical bases, complexities, and expected accuracies in simulating the dynamics of water flow. Models using more mathematical terms in the flow-governing equations are more physically based and expected to be more accurate than models using approximations, however, are more complex due to more intensive but approximate numerical schemes (inefficient). Models using approximate equations with analytical solutions may provide a balance between complexity and accuracy. The review and comparisons are useful to modellers, water resources managers, and researchers in understanding the basic foundations of the models and making informed selections for practical applications or further developments. Other factors such as data intensiveness, user friendliness, and resource requirements are also important considerations. Copyright © 2011 John Wiley & Sons, Ltd.

Modeling watershed rainfall–runoff relations using impervious surface-area data with high spatial resolution

A distributed object-based rainfall–runoff simulation (DORS) model with incorporation of detailed impervious surface-area (ISA) data, derived from digital true-color orthophotography data with high spatial resolution, was developed. This physically based model simulates hydrologic processes of precipitation interception, infiltration, runoff, evapotranspiration, change of soil moisture, change of water-table depth, runoff routing, groundwater routing, and channel-flow routing. The modeling processes take objects based on land-cover types as fundamental spatial units in order to reduce data volume, increase computational efficiency, strengthen representation of watersheds, and utilize the data in variable scales. US Geological Survey stream-gaging data were used to validate the temporal variation of simulated discharge within two watersheds in Rhode Island State. The ratio of absolute error to the mean and the Nash coefficient in the validation period are 7.2% and 0.90 for the first watershed, and 8.0% and 0.77 for the second watershed, respectively. The results indicate that the DORS model is able to capture the relationship between rainfall and runoff in the study area, and that it is applicable in the further study of ISA impacts on the water cycle and associated pollution problems. The results also demonstrate that the performance of the hydrologic simulation is improved with ISA data with high spatial resolution.

Enhancement of the channel routing module in SWAT

AbstractThe objective of this study is to demonstrate that the channel flow routing techniques used in the Soil and Water Assessment Tool (SWAT) can be sometimes inappropriate for runoff simulation in small basins. Simulated hydrographs have a tendency to underestimate peak flows or may send a false signal during the recession periods when SWAT is applied to the Mihocheon Basin in South Korea. This was particularly evident for sub‐basins that had a short travel time of much less than a day. In order to enhance the channel routing module in SWAT, an alternative routing technique in which Manning relationship is combined with a simple channel reach continuity equation is proposed in the present study. The advantage of the proposed routing technique is that parameters are readily available from channel morphological data and that it is applicable to small basins. Through simulations of specific events, this routing module that is incorporated into SWAT is almost free from instability errors and produces realistic flow depths and velocities unlike the original version of SWAT with Muskingum method. Copyright © 2009 John Wiley & Sons, Ltd.

Real-Time Flood Forecasting System Based on Simple Lumped Rainfall-Runoff Models Combined with Channel Flow Routing Model Using Particle Filter

Real-Time Flood Forecasting System Based on Simple Lumped Rainfall-Runoff Models Combined with Channel Flow Routing Model Using Particle Filter

A modified morphodynamic model for investigating the response of rivers to short-term climate change

Near-future climate change will affect the discharge and base level of rivers and thus cause channel changes. The nature and pace of such changes can be simulated using morphodynamic models. As part of an investigation of how the changing hydrology of the St-Lawrence River, Quebec, Canada, will affect its tributaries we have made additions and modifications to a one-dimensional morphodynamic model developed for gravel-bed rivers (SEDROUT). The changes allow simulation of sand-bed rivers, variable discharge, downstream water level fluctuations, and flow and sediment routing in channels with islands. A revised formulation for calculating the grain size distributions of the surface and subsurface material is presented to allow for alternating sedimentation and erosion. We test the enhanced model using small-scale simulations and present-day conditions in four tributaries of the St-Lawrence River. The model is calibrated and validated for the tributaries and the capability to simulate river morphology over a 100-year period is tested. Good validation agreement on water level, cross-sectional mean velocity, and sediment transport rate is obtained for the four tributaries of the St-Lawrence River. With these modifications, modelling a very wide range of river morphodynamic problems is now possible.

Digital Yellow River Model

Soil erosion is one of the key concerns in land use management for the Loess Plateau of the Yellow River, where serious soil loss is the root cause of environmental and ecological degradation of the basin. In this paper, a physically-based, distributed-parameter, and continuous erosion prediction model at the river basin scale was developed with the aim of assisting in developing better land use management strategies. The framework, the major supporting techniques, and the typical erosion processes are described. The physical processes of sediment yield and transport in the Loess Plateau are divided into three sub-processes, including the runoff and sediment yield on hillslopes, gravitational erosion in gullies, and hyperconcentrated flow routing in channels. For each sub-process, a physically-based simulation model was developed and embedded into the whole model system. The model system was applied to simulate the runoff and sediment yield in several typical years in the coarse sediment source area of the Loess Plateau, and the simulated results were in reasonably good agreement with the measured values.

Impulse response of a linear diffusion analogy model as a flood frequency probability density function

The impulse response of a linear convective-diffusion analogy (LD) model used for flow routing in open channels is proposed as a probability distribution for flood frequency analysis. The flood frequency model has two parameters, which are derived using the methods of moments and maximum likelihood. Also derived are errors in quantiles for these parameter estimation methods. The distribution shows that the two methods are equivalent in terms of producing mean values—the important property in case of unknown true distribution function. The flood frequency model is tested using annual peak discharges for the gauging sections of 39 Polish rivers where the average value of the ratio of the coefficient of skewness to the coefficient of variation equals about 2.52, a value closer to the ratio of the LD model than to the gamma or the lognormal model. The likelihood ratio indicates the preference of the LD over the lognormal for 27 out of 39 cases. It is found that the proposed flood frequency model represents flood frequency characteristics well (measured by the moment ratio) when the LD flood routing model is likely to be the best of all linear flow routing models.