Removing sediment transport in open channel with submerged aquatic vegetation: Laboratory study.

Vegetation affects fluvial processes and is key role in river management in particular sediment transport. Vegetation characteristics such as vegetation’s density, height and distributions have significant effect on sediment transport in vegetated channel. This paper studied the role of aquatic vegetation characteristics in sediment transport. Laboratory experiments were conducted in a fabricated channel with real vegetations (Hydrilla verticillata) planted on its bed. The total suspended solid (TSS) was applied for sediment rate measurement. As results, it is found that vegetation density and distribution has significant impact to the sediment entrapment capacity of the vegetation. An increased coverage of the vegetation from 33 to 66% of the flow area has increased the sediment trapping capacity in average by 15%. To sum up, the present study was designed to determine the effect of the vegetation properties on sediment transport rate

Numerical solution for open channel flow with submerged flexible vegetation

The purpose of this study is to explore the suitability of numerical models in estimation o f velocity and flow resistance (Manning n) in open channels with totally submerged flexible vegetation. A three dimensional (3D) numerical model based on arbitrary Lagrangian-Eulerian (ALE) approach has been employed to simulate the effects of various characteristics of selected flexible vegetations to the velocity distribution and flow resistance. The modeling involved simultaneous solution of Navier Stokes equation f or o pen channel flow, s tress-strain relationship for the vegetation structure and ALE algorithm for the moving vegetation boundaries. The numerical computation has been carried out with a n aid of a commercial finite element software package, COMSOL Multiphysics 3.4. The numerical results were validated using experimental data carried out in the laboratory using real vegetations. The accuracy of numerical model compared t o experimental results w as measured in terms of mean absolute error (MAE). The results show that the numerical model which combined the three applications as mentioned above able to predict the velocity and the flow resistance coefficient in open vegetated channel with reasonable accuracy. The MAE calculated for velocity and Manning n is ±0.02

Dam breach parameters and their influence on flood hydrographs for Mosul dam

Dams breach geometry prediction is crucial in dam break studies. The characteristics of flood hydrographs resulting from a dam breach essentially depend on the breach geometry and the required time for breach formation. To investigate the impact of breach parameters on maximum breaching outflows, five breach prediction approaches were implemented to calculate the flood hydrographs using HEC-RAS model, for Mosul dam. Numerous reservoir water levels for each approach were considered. Sensitivity analysis was carried out to evaluate the effect of each parameter on the resulting flood hydrographs. The time and value of peak discharge for each scenario were analysed and discussed. Results show that the most suitable method for estimating breach parameters for Mosul dam was the Froehlich approach. Furthermore, the sensitivity analysis shows that the breach side slope does not affect the peak discharge time and has a minor influence on peak outflow values. Meanwhile, the required time for the breach to develop was highly sensitive to both peak discharge and peak discharge time

Development of ultra high-performance fiber reinforced concrete barge for 5 MW wind turbine

Floating wind turbines are gaining more popularity today as one of the effective green energy harvesting systems. In the effort to reduce the cost of construction for floating wind turbines, concrete support structures and concrete barge have been developed. However, due to the concrete low tensile strength and susceptibility to chemical action and freezing temperatures, the concrete barges are designed with very large sections resulting in high energy consumption, high volume of construction materials, weightier structure and more heavy equipment for fabrication and installation. Therefore, in order to overcome these challenges, in this study Ultra High-Performance Fiber Reinforced Concrete (UHPFRC) is proposed for use in casting a barge for a floating offshore wind turbine and compared to a reinforced cement concrete (RCC) barge. The experimental tests conducted on the UHPFRC and RCC barge small sized prototypes, showed less heel on the RCC barge compared to the UHPFRC barge. However, the RCC barge experienced severe green water load which could cause it to capsize. The hydrodynamic analysis results from the finite element analysis showed less pitch motions in the UHPFRC barge in 7 out of the 12 DLCs considered. The roll motions were less than 50 in both barges with insignificant difference between them, while in heave motions, the UHPFRC barge experienced 10% to 20% less motions than the RCC barge in all 12 DLCs. In the structural analysis, the maximum deformation of the UHPFRC barge was 14 mm, which is 129% higher than the deformation of the RCC barge. In overall, the UHPFRC barge proved to be more effective in achieving better hydrodynamic motions for the barge floater in comparison to the RCC barge and can be considered as alternative to the conventional reinforced cement concrete material

Modelling the effect of sediment coarseness on local scour at wide bridge piers

Experimental data from a physical model of scouring around a cylindrical wide pier embedded in two types of uniform sediment beds are presented. The effects of sediment sizes and various pier widths on scour development and equilibrium scour depth of wide bridge piers are described. Existing literature suggest that the empirical scour prediction equations based on laboratory data over-predict scour depths for large structures. The present study has attempted to fill this gap for a cylindrical wide pier. Further, equations for the estimation of non-dimensional maximum scour depth for a wide cylindrical pier embedded in uniform sediment were proposed as functions of the sediment coarseness

Review of remote sensing and geospatial technologies in estimating rooftop rainwater harvesting (RRWH) quality

Rooftop rainwater harvesting (RRWH) systems can provide low-cost decentralized water to urban and rural households that have no access to treated water. These systems are considered the key strategic adoption measures for communities affected by climate change. Roofing materials, roofing conditions, roofing geometry, weather conditions, and land use/land cover (LULC) conditions can significantly affect the quality of RRWH. Therefore, the effects of these factors on RRWH quality must be analyzed carefully. Remote sensing and Geographical Information System (GIS) have been widely used in urban environmental analysis. However, these technologies have never been used to analyze, map, and model the effect of various factors on RRWH quality. This review determines the research gaps in the use of geospatial technologies in estimating RRWH quality and simulate the implications of roofing materials and roofing surface conditions towards the urban environment. An approach for the integrated use of remote sensing and GIS to assess the quality of RRWH is also proposed

Flow in a Branching Open Channel: A Review

Branching channel flow refers to any side water withdrawals from rivers or main channels. Branching channels have wide application in many practical projects, such as irrigation and drainage network systems, water and waste water treatment plants, and many water resources projects. In the last decades, extensive theoretical and experimental investigations of the branching open channels have been carried out to understand the characteristics of this branching flow, varying from case studies to theoretical and experimental investigations. The objectives of this paper are to review and summarise the relevant literatures regarding branching channel flow. These literatures were reviewed based on flow characteristics, physical characteristics, and modeling of the branching flow. Investigations of the flow into branching channel show that the branching discharge depends on many interlinked parameters. It increases with the decreasing of the main channel flow velocity and Froude number at the upstream of the branch channel junction. Also it increases with the increasing of the branch channel bed slope. In subcritical flow, water depth in the branch channel is always lower than the main channel water depth. The flow diversion to the branch channel leads to an increase of water depth at the downstream of the main channel. From the review, it is important to highlight that most of the study concentrated on flow characteristics in a right angle branch channel with a rigid boundary. Investigations on different branching angles with movable bed have still to be explored

Modeling the infiltration capacity of permeable stormwater channels with a check dam system

The use of permeable stormwater channels has introduced concerns over the effects of infiltration on the hydraulic behavior of their flow and the effects of flow hydraulic conditions (e.g., the water level, channel section, flow velocity, and vegetation) on the channel infiltration capacity. A check dam system provides backwater ponding, which increases the flow water depth along a channel. In this study, a channel model was used to investigate the variation in the infiltration capacity of permeable stormwater channels under different flow hydraulic conditions. Increasing the downstream check dam height and using a grass cover increased the infiltration rate and cumulative infiltration because of the decreased velocity and increased flow depth. The presence of subsurface water did not affect the hydraulic characteristics of the channel flow but decreased the cumulative infiltration because of the fast saturation of the soil. An empirical equation was developed for predicting the infiltration capacity of grassed channels in which four hydraulic parameters (i.e., the water depth, base width, side slope, and velocity) are introduced to the modified Kostiakov model. The developed model was used to calculate the runoff reduction due to infiltration along a grassed channel with and without a check dam system. The percentage of infiltrated water increased from 8 to 14% with the check dam system. The developed model can be used to predict the infiltration capacity of permeable channels for improved stormwater management and provides a valuable decision support tool for permeable channel design

Modified models for better prediction of infiltration rates in trapezoidal permeable stormwater channels

In stormwater management, it is important to accurately quantify the infiltration rates to solve urban runoff-related problems. This study proposes a method to improve estimates of the infiltration rate in permeable stormwater channels. As part of the analysis, five infiltration models were evaluated: the Kostiakov, Horton, modified Kostiakov, Philip and SCS (Soil Conservation Service) models. Infiltration tests with various initial water levels were performed on channel models with differing base width and side slopes. The results show that the addition of three parameters that describe the trapezoidal cross-sectional area, i.e. the depth, side slope and base width, in the infiltration models yielded better estimates of the infiltration rate. A comparison of the infiltration capacity values obtained from the models after the three parameters were added with those that were experimentally obtained, shows that the improved modified Kostiakov model is the most suitable model to predict infiltration rates in trapezoidal permeable stormwater channels

Testing the accuracy of sediment transport equations using field data

In order to recommend the equations that can accurately predict sediment transport rate in channels, selected sediment transport equations (for estimating bed load and suspended load) are assessed using field data for 10 rivers around the world. The tested bed load equations are Einstein, Bagnold, Du Boys, Shield, Meyer-Peter, Kalinskie, Meyer-Peter Muller, Schoklitsch, Van Rijin, and Cheng. Assessment show that Einstein and Meyer-Peter Muller equations have the least error in their prediction compared with the other tested equations. Based on the field data, each of Einstein and Meyer-Peter Muller equations gave the most accurate bed load estimations for three rivers while Schoklitsch equation and Du boys equation gave the most accurate bed load estimations for two rivers and one river respectively. The lowest values of Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were obtained from the applying Einstein equation for estimating bed load for Oak Creek River and these values were found to be 0.02 and 0.04 respectively. On the other hand, the tested equations for predicting suspended load are Einstein, Bagnold, Lane and Kalinske, Brook, Chang, Simons and Richardson, and Van Rijin. Among the above tested equations, assessment show that Bagnold, Einstein and Van Rijin gave the most accurate estimation for the suspended load. The lowest values of Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were obtained from applying Bagnold equation and these values were found to be 0.012 and 0.015 respectively