Evaluation of Flood Routing Models and Their Relationship to The Hydraulic Properties of The Diyala River Bed

In this study, four types of flood routing approaches were studied which give significantly varied results represented by the differences between computed and observed flows and also differ considerably on the friction coefficient and bed slope of the channels. First two approaches use a hydraulic solution to solve the equations of unsteady flow, while the third approach uses the hydrological solution, and the fourth algorithm solves Muskingum approach with seven parameters. All these approaches were run with the same input parameters, the results were compared and tested with four Error Measurement Indices, Sum of Squared Deviations, Error of Peak Discharge, Variance Index, and agreement index. Diyala River was selected for this application. Dynamic wave method gave accurate results, followed by the characteristic method, and then the linear Muskingum-Cunge method, but Symbiotic Organisms Search Algorithm not gave any senses due to change in roughness or bed slope and gave very identical values with recorded outflow in all conditions, which means that the hydraulic solution is better compared to the hydrological solution. The results also showed that the difference between the calculated and observed flows diminished with a decrease in the coefficient of friction and an increase in the bed slope channel.

PENENTUAN POLA OPERASI PINTU PELIMPAH DALAM RANGKA PENGENDALIAN BANJIR BENDUNGAN DELINGAN, JAWA TENGAH

A spillway is one of many important components of a dam, which is operated to prevent the dam from overtopping. Spillway with gate structures requires to have a good operation pattern by considering a minimum critical height and outflow discharge to prevent any flooding events in the downstream part of the spillway channel. The case study in this research is the Delingan Dam which has two ogee spillways, four main sluice gates and four additional sluice gates. Located in Karanganyar District, West Java, Delingan Dam is considered as a vast infrastructure which is potentially threatening if the spillway’s operation is not optimal. This study aims to analyze the spillway gate operations’ pattern of Delingan Dam in order to control the flooding event. The methodology used in this study is flood routing by utilizing several scenarios in order to obtain the optimal simulation results. Five scenarios that were simulated on the designated flood discharge have various combinations on the number of gates and their opening, as well as the time in which the operation started. The results show that the operation only using ogee spillway still meets the criteria for minimum critical height and maximum allowable discharge for return period of 25, 50, and 100 year.As the discharge with 1000 year return period, half of PMF, and PMF,the recommended operation is, foremost, to occupy the main gate in which results in the peak outflow discharge of 23.65 m3/s, 62.4 m3/s, and 140.9 m3/s, with the minimum critical height of 1.45 m, 1.41 m, and 1.35 m, respectively. However, this operation is not adequate for the half of PMF, and the PMF discharge, since the capacity in the spillway channel is estimated about 24.7 m3/s.Keywords: spillway, flood control, spillway gate operation, the delingan dam

A new method for dividing flood period in the variable-parameter Muskingum models

The Muskingum routing model is favored by water engineers owing to its simplicity and accuracy. A large amount of research is done to improve the accuracy of the model. One way to do so is to consider variable hydrological parameters during the flood routing period. In this study, the random selection (RS) method was proposed to divide the flood period of the nonlinear Muskingum model into three sub-periods. The proposed method was based on RS of members in each sub-region. It was applied to rout three flood hydrographs, and the objective function was the sum of squared errors. Comparing the results from the three variable-parameter nonlinear Muskingum model with those from the variable-parameter nonlinear Muskingum models in previous studies, the proposed model optimized the objective function in these hydrographs up to 61%. The uncertainty analysis of Muskingum parameters for Wilson's hydrograph was performed by the fuzzy alpha cut method, and it was found that the uncertainty of the parameter x is greater than the uncertainty of the parameters k and m.

A new formula for predicting movable bed roughness coefficient in the Middle Yangtze River

Computing movable bed roughness plays an important role in the modeling of flood routing and bed deformation, and the magnitude of movable bed roughness is closely associated with complex bedform configurations that change with the sand wave motion. The motion of sand wave is dependent on the incoming flow and sediment conditions and channel boundary. After the operation of the Three Gorges Project, the flow and sediment regime changed remarkably in the Middle Yangtze River (MYR), followed by significant channel adjustments. A dramatic decrease in sediment concentration caused continuous channel degradation and significant variations in cross-sectional profiles of the MYR. These adjustments in the channel boundary influence the motion of sand wave, which can further affect the magnitude of movable bed roughness. A new formula for predicting the movable bed roughness coefficient is developed, which can be expressed by a power function of both Froude number and relative water depth. The proposed formula was first calibrated using 1266 datasets of measurements at five hydrometric stations in the MYR during 2001–2012. A back-calculation process shows that the roughness coefficients calculated by the proposed formula agree well with the observations, with the determination coefficient being equal to 0.88. The proposed formula was further verified using 651 datasets of measurements at these hydrometric stations during 2013–2017. Furthermore, four common roughness formulas selected from the literature were tested for comparison. The results indicate that the calculation accuracy of the proposed formula is significantly higher than that of the previous formulas, and the Manning roughness coefficients predicted by the proposed formula have the errors less than ±30% for 96% of the datasets. Therefore, the new bed roughness predictor proposed in this study can accurately calculate the roughness coefficients straightforwardly without iterative solution and graphical interpolation, and the parameters required in the roughness predictor are easily obtained from the hydrometric observations.

Optimization of the Nonlinear Muskingum Model Parameters for the River Routing, Tigris River a Case Study

Flood forecasting and management are one of the most important strategies necessary for water resource and decision planners in combating flood problems. The Muskingum model is one of the most popular and widely used applications for the purpose of predicting flood routing. The particle swarm optimization (PSO) methodology was used to estimate the coefficients of the nonlinear Muskingum model in this study, comparing the results with the methods of genetic algorithm (GA), harmony search (HS), least-squares method (LSM), and Hook-Jeeves (HJ). The average monthly inflow for the Tigris River upstream at the Al-Mosul dam was selected as a case study for estimating the Muskingum model's parameters. The analytical and statistical results showed that the PSO method is the best application and corresponds to the results of the Muskingum model, followed by the genetic algorithm method, according to the following general descending sequence: PSO, GA, LSM, HJ, HS. The PSO method is characterized by its accurate results and does not require many assumptions and conditions for its application, which facilitates its use a lot in the subject of hydrology. Therefore, it is better to recommend further research in the use of this method in the implementation of future studies and applications.

Detention Reservoir: Proposal for Flood Control in the Ipiranga Stream Basin, Juiz de Fora, MG, Brazil

In order to provide parameters for sizing a damping reservoir, which was intended to control the floods that occur in the Ipiranga Stream basin, a routine developed in Visual Basic for Applications (VBA) is used. From the identification of the most critical point of the flood, hydrological flow data are presented, estimated by dividing the basin into sub-basins, using the Rational method, resulting in a value of flow higher than the admissible one for the stream channel. The method used in dimensioning the reservoir was flood routing. After making a pre-selection of the most interesting place to position the reservoir, insertions of the situation existent were made to the VBA application, in order to generate scenarios and enable the choice of an ideal situation, in view of the presented constraints. A very acceptable and feasible result is pointed out, indicating general parameters for sizing a reservoir to control floods in the Ipiranga Stream basin.

Assessment of NEWMAP Effects on Gully Erosion Control and Environmental Development over South East, Nigeria

The potential impacts of gully erosion over South Eastern Nigeria are a worrisome scenario. It has resulted in the displacement of millions of habitats, agricultural, and economic losses. The result of the effect of Nigerian Erosion Watershed Management Project (NEWMAP) monitoring and evaluation on the effect of gully erosion on economic development in this study has revealed a positive significant influence at P < 0.05 over the study region. Also, it is revealed that NEWMAP programmes have significantly covered some constructions of hydraulic structures for flood routing and soil erosion control in South East, Nigeria. This intervention has significantly reduced the rate of land degradation occasioned by soil erosion, protection of watershed and agricultural land, which has thus been responsible for improved agricultural production. In conclusion, it is imperative to conduct periodic monitoring and evaluation of the activities of NEWMAP to building a strong evidence-based mechanism that enhances assessment of the diverse range of intervention projects on the dwellers of South-East extraction.

Assessment of NEWMAP Effects on Gully Erosion Control and Environmental Development over South East, Nigeria

The potential impacts of gully erosion over South Eastern Nigeria are a worrisome scenario. It has resulted in the displacement of millions of habitats, agricultural, and economic losses. The result of the effect of Nigerian Erosion Watershed Management Project (NEWMAP) monitoring and evaluation on the effect of gully erosion on economic development in this study has revealed a positive significant influence at P < 0.05 over the study region. Also, it is revealed that NEWMAP programmes have significantly covered some constructions of hydraulic structures for flood routing and soil erosion control in South East, Nigeria. This intervention has significantly reduced the rate of land degradation occasioned by soil erosion, protection of watershed and agricultural land, which has thus been responsible for improved agricultural production. In conclusion, it is imperative to conduct periodic monitoring and evaluation of the activities of NEWMAP to building a strong evidence-based mechanism that enhances assessment of the diverse range of intervention projects on the dwellers of South-East extraction.

Development of a New 8-Parameter Muskingum Flood Routing Model with Modified Inflows

Flood routing can be subclassified into hydraulic and hydrologic flood routing; the former yields accurate values but requires a large amount of data and complex calculations. The latter, in contrast, requires only inflow and outflow data, and has a simpler calculation process than the hydraulic one. The Muskingum model is a representative hydrologic flood routing model, and various versions of Muskingum flood routing models have been studied. The new Muskingum flood routing model considers inflows at previous and next time during the calculation of the inflow and storage. The self-adaptive vision correction algorithm is used to calculate the parameters of the proposed model. The new model leads to a smaller error compared to the existing Muskingum flood routing models in various flood data. The sum of squares obtained by applying the new model to Wilson’s flood data, Wang’s flood data, the flood data of River Wye from December 1960, Sutculer flood data, and the flood data of River Wyre from October 1982 were 4.11, 759.79, 18,816.99, 217.73, 38.81 (m3/s)2, respectively. The magnitude of error for different types of flood data may be different, but the error may be large if the flow rate of the flood data is large.