Parameter optimization in modelling unsteady compound channel flows

1992 ◽  
Vol 19 (3) ◽  
pp. 441-446 ◽  
Author(s):  
Habib Abida ◽  
Ronald D. Townsend
Keyword(s):  
Parameter Optimization ◽  
Optimization Methods ◽  
Flood Plain ◽  
Flood Routing ◽  
Compound Channel ◽  
Flood Events ◽  
Channel Section ◽  
Simplex Methods ◽  
Boundary Roughness ◽  
Good Agreement

Optimization methods are used to estimate data for routing floods through open compound channels (main channels with flood plain zones). These data include the irregular channel section geometry and the varying boundary roughness. Differences between simulated and observed stages and discharges are minimized using three optimization algorithms: Powell's method, Rosenbrock's algorithm, and the Nelder and Meade simplex method. Powells' method performed poorly; however, both the Rosenbrock and simplex methods yielded good results. The estimated data using the Rosenbrock and simplex methods were used to route different flood events observed in a laboratory channel. Simulated peak stages and discharges were in good agreement with those estimated using actual routing data. Key words: compound channel, flood routing, lateral momentum transfer, optimization, unsteady flow.

Evaluation of adapted hydrological flood routing approaches as a cost-efficient contribution for the assessment of nature-based flood mitigation measures

2020 ◽  
Author(s):  
Fabian Merk ◽  
Michael Neumayer ◽  
Sonja Teschemacher ◽  
Markus Disse
Keyword(s):  
River Restoration ◽  
Hydrological Model ◽  
Flood Plain ◽  
Flood Routing ◽  
Flood Mitigation ◽  
Mitigation Measures ◽  
Hydrological Models ◽  
Flood Events ◽  
Hydrodynamic Models ◽  
Cost Efficient

<p>Nature-based retention measures are an essential part of a sustainable and integrated flood protection strategy and can contribute to a holistic flood mitigation approach. Thereby river restoration measures such as channel widening, or flow path extension to increase the channel meandering represent successfully used components. Coupled with flood plain measures, retarding and retention effects of flood events are possible. These effects are commonly computed applying two-dimensional hydrodynamic modelling approaches. However, these developments rely on high spatial and temporal resolutions which are generally characterized by a high computational demand and are hence time and cost expensive. Thus, the evaluation and derivation of flood routing parameters to reproduce the resulting hydrodynamical processes in hydrological models can provide an effective and fast computation of river restoration scenarios.</p><p> </p><p>The objective in the present study is the derivation and application of flood routing parameters which can account for the effects of river restoration and flood plain measures in hydrological models. Further, this study aims to determine if the catchment and scale specific outcomes and parameter sets are also applicable to a broader range of catchments.</p><p>For this purpose, commonly applied flood routing approaches and the associated parameters used in hydrological models (e.g. the kinematic wave approach in the WaSiM model) are investigated for catchments of different scales in Bavaria (Germany) and for flood events of varying characteristics (e.g. return period, flood volume). To determine the effects of channel restoration and flood plain measures, two-dimensional hydrodynamic models (HYDRO_AS-2D) are set up to simulate the current state as well as restoration scenarios. Based on the simulation results of the hydrodynamic models, the parameters of the flood routing approaches are calibrated to match the catchment specific restoration effects for a first set of river sections. Catchment and scale dependent parameter sets (dominating valley type, flood plain slopes) are then derived to reproduce the specific river restoration. First results of the calibration of the parameter sets show a satisfying fit of the hydrological model to different restoration scenarios of the hydrodynamic model. For the validation of the derived parameter sets of the flood routing methods in the hydrological model additional river sections of the hydrodynamic models are subsequently investigated.</p><p>The implementation of the new flood routing parametrization of the hydrological models is finally examined as an alternative resource efficient way of calculating the effects of river restoration scenarios. Moreover, the applicability of the outcomes as a cost-efficient alternative compared to hydrodynamic models in land use planning and risk assessment is assessed and discussed within the frame of river restorations as flood mitigation measures.</p>

scholarly journals Exploration of Semantic Geo-Object Recognition Based on the Scale Parameter Optimization Method for Remote Sensing Images

2021 ◽  
Vol 10 (6) ◽  
pp. 420
Author(s):  
Jun Wang ◽  
Lili Jiang ◽  
Qingwen Qi ◽  
Yongji Wang
Keyword(s):  
Parameter Optimization ◽  
Scale Parameter ◽  
Human Perception ◽  
Optimization Methods ◽  
Optimization Method ◽  
Initiation Point ◽  
Scale Parameters ◽  
Object Based ◽  
Geographic Object ◽  
Multiresolution Segmentation

Image segmentation is of significance because it can provide objects that are the minimum analysis units for geographic object-based image analysis (GEOBIA). Most segmentation methods usually set parameters to identify geo-objects, and different parameter settings lead to different segmentation results; thus, parameter optimization is critical to obtain satisfactory segmentation results. Currently, many parameter optimization methods have been developed and successfully applied to the identification of single geo-objects. However, few studies have focused on the recognition of the union of different types of geo-objects (semantic geo-objects), such as a park. The recognition of semantic geo-objects is likely more crucial than that of single geo-objects because the former type of recognition is more correlated with the human perception. This paper proposes an approach to recognize semantic geo-objects. The key concept is that a single geo-object is the smallest component unit of a semantic geo-object, and semantic geo-objects are recognized by iteratively merging single geo-objects. Thus, the optimal scale of the semantic geo-objects is determined by iteratively recognizing the optimal scales of single geo-objects and using them as the initiation point of the reset scale parameter optimization interval. In this paper, we adopt the multiresolution segmentation (MRS) method to segment Gaofen-1 images and tested three scale parameter optimization methods to validate the proposed approach. The results show that the proposed approach can determine the scale parameters, which can produce semantic geo-objects.

A Modified Chezy Formula for One-Dimensional Unsteady Frictional Resistance in Open Channel Flow

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Junwei Zhou ◽  
Weimin Bao ◽  
Geoffrey R. Tick ◽  
Hamed Moftakhari ◽  
Yu Li ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Frictional Resistance ◽  
Mitigation Strategies ◽  
Flood Routing ◽  
Flood Events ◽  
Complex Flow ◽  
Cross Sectional ◽  
Friction Resistance ◽  
Flow Unsteadiness ◽  
Better Than

Abstract It has been observed in literature that for unsteady flow conditions the one-to-one relationships between flow depth, cross-sectional averaged velocity, and frictional resistance as determined from steady uniform flow cases may not be appropriate for these more complex flow systems. Thus, a general friction resistance formula needs to be modified through the addition of new descriptive terms to account for flow unsteadiness, in order to eliminate errors due to uniform and steady-flow assumptions. An extended Chezy formula incorporating both time and space partial derivatives of hydraulic parameters was developed using dimensional analysis to investigate the relationship between flow unsteadiness and friction resistance. Results show that the proposed formula performs better than the traditional Chezy formula for simulating real hydrograph cases whereby both formula coefficients are individually identified for each flood event and coefficients are predetermined using other flood events as calibration cases. Although the extended Chezy formula as well as the original Chezy formula perform worse with the increasing degree of flow unsteadiness, its results are less dramatically affected by unsteadiness intensity, thereby improving estimations of flood routing. As a result, it tends to perform much better than traditional Chezy formula for severe flood events. Under more complex conditions whereby peak flooding events may occur predominantly under unsteady flow, the extended Chezy model may provide as a valuable tool for researchers, practitioners, and water managers for assessing and predicting impacts for flooding and for the development of more appropriate mitigation strategies and more accurate risk assessments.

scholarly journals Simulations of Depth-Averaged Streamwise Velocity of Meandering Compound Channel using TELEMAC Modules

2018 ◽  
Vol 65 ◽  
pp. 07001
Author(s):  
Abdul Haslim Abdul Shukor Lim ◽  
Zulhilmi Ismai ◽  
Mohamad Hidayat Jama ◽  
Md. Ridzuan Makhtar
Keyword(s):  
Stokes Equations ◽  
Computing Time ◽  
Streamwise Velocity ◽  
Main Channel ◽  
Navier Stokes ◽  
Relative Depth ◽  
Compound Channel ◽  
Navier Stokes Equations ◽  
Numerical Tools ◽  
Good Agreement

Capabilities of numerical tools to simulate fluid problems significantly depend on its methods to solve for the Navier-Stokes equations. Different dimensional computing tools using the same horizontal meshes were used to simulate flow conditions inside non- and vegetation meandering compound channel. Both tools give good agreement for simulations of depth-averaged streamwise velocity inside the main channel, but its capabilities vary significantly for simulations on floodplains. Lower relative depth recorded a higher percentage of errors than flow with higher relative depth. Vegetation along the main channel increased the flows complexity especially in the area near the vegetation thus reducing the simulation capabilities of the computing tools. Simulations work by TELEMAC-3D significantly better in the areas with highly dimensional and turbulence conditions. TELEMAC-2D is still useful because of its simplicity and lower computing time and resources required.

Gravel-Pit Lakes Connected with the River Rhine as a Reserve for High Productivity of Plankton and Young Fish

1994 ◽  
Vol 29 (3) ◽  
pp. 267-271 ◽  
Author(s):  
D. Neumann ◽  
Chr Seidenberg-Busse ◽  
A. Petermeier ◽  
St Staas ◽  
F. Molls ◽  
...  
Keyword(s):  
Flood Plain ◽  
River Rhine ◽  
Flood Events ◽  
Eutrophic Lakes ◽  
Field Station ◽  
High Productivity ◽  
Sand And Gravel ◽  
The University ◽  
Lentic Waters ◽  
Lower Rhine

During the last two decades an increasing number of sand and gravel-pits were established in the original flood plain of the River Rhine. Some of these are connected with the stream by a small canal for the transport of the spoil. Some of these dredged lakes have been studied during recent years at the ecological field station of the University of Köln, with regard to seasonal phytoplankton succession, productivity of copepods and cladocerans, occurrence of macrozoobenthos, and both spawning and recruitment of fish populations. These eutrophic lakes represent a valuable substitute biotope for lost lentic waters of the former flood plain. They offer via the canal connection an advantageous habitat to resident fish species of the Lower Rhine, (1) for reproduction and growth of the 0+-generation, and (2) for shelter during flood events. Recommendations for reclamation plans of such lakes are required.

scholarly journals Comparison of parameter optimization methods for quantitative susceptibility mapping

2020 ◽  
Vol 85 (1) ◽  
pp. 480-494 ◽  
Author(s):  
Carlos Milovic ◽  
Claudia Prieto ◽  
Berkin Bilgic ◽  
Sergio Uribe ◽  
Julio Acosta‐Cabronero ◽  
...  
Keyword(s):  
Parameter Optimization ◽  
Optimization Methods ◽  
Susceptibility Mapping ◽  
Quantitative Susceptibility Mapping
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