Redesain Bendung Semat Kali Gawe Kabupaten Jepara 2025

For Engineers involved in planning and construction of water resources building, hydrology becomes very important data. In terms of planning stage in water resources especially waterworks, it is known that design flood discharge closed to field realistic conditions is often needed in order that a planned construction is able to control flood discharge. Several previous researches in choosing flood discharge selection method have diverse depending on observed watershed. One method in determining selected flood discharge by verification using Creager diagram, by comparing discharge calculation results of several Synthetic Unit Hydrograph (SUH) with infrastructure flood discharge (AWLR result) in observation point. This research aims to obtain the most suitable synthetic unit hydrograph and close to analysis result of measured discharge frequency, and Creager diagram in Kelara watershed (DAS). Based on the calculation of design flood discharge according to rainfall data using synthetic unit hydrograph of Nakayasu, ITB I, ITB II, and SCS (HEC-HMS) as well as the calculation of design flood discharge according to collected data, it is concluded that the synthetic unit hydrograph method closest to design flood discharge with measured discharge rate and Q1000 rate of Creager diagram is SCS. Flood discharge rate obtained according to HSS SCS method using HEC-HMS 4.8 application in period of 2 years is 658,40 m3/s, 25 years is 682,70 m3/s, 50 years is 787,00 m3/s, 100 years is 885,70 m3/det, and 1000 years is 1202,60 m3/s

Floods occur due to several factors including topographic conditions, high rainfall intensity, blockage of water flow, lack of water infiltration areas, deforestation, and so on. The Tojo watershed is included in the Parigi-Poso river area, with an area of 211,830 km2 and a river length of 25.52 km. In the Tojo watershed, it is necessary to study flooding, because the watershed always flows every year. This research aims to find out how much flood discharge was obtained from the analysis of the Tojo watershed design flood with the Gama I synthetic unit hydrograph method and to find out how much the Gama I synthetic unit hydrograph analysis compared to the design flood discharge based on river discharge data (AWLR). From the calculation results obtained a comparison between the design flood discharge value processed by rainfall data using the Gama I Synthetic Unit Hydrograph method to the design flood discharge value processed by the Tojo river discharge data using the log person III distribution method for a 2 year return period is 1957,45 %, for the 5-year return period is 1347,64 %, for the 10 year return period is 1224,65 %, for the 25 year return period is 1169,96 %, for the 50 year return period is 1165,67 % and for the 100 years is 1178,75 %.

Design discharge is discharge with a certain return period which is used as a reference or parameter in a water building construction planning. Calculation of the design discharge can be done by using the synthetic unit hydrograph method. The calculation of the planned discharge using the Nakayasu and SCS-CN synthetic unit hydrographs aims to compare the calculation of the maximum discharge in the Pesung Watershed, Batam. The design discharge analysis was carried out without calibrating with AWLR data (observed flow) due to the unavailability of AWLR data at the study site. Thus, in this study using HDRO (high direct runoff) as a comparison. The purpose of this study is to estimate the magnitude of the design flood discharge in the Pesung Watershed, Batam City. The methods used in this calculation of the flood hydrograph is using an empirical formula, namely SCS Synthetic Unit Hydrograph and Nakayasu. The results of the HDRO calculation analysis show that the largest flood discharge occurs in the Nakayasu synthetic unit hydrograph method with details of the SCS synthetic unit hydrograph method, the peak time (Tp) is obtained at 4.46 hours, with a return period flood discharge of 5 – 50 reaching 215,488 – 584,308 m3/ s. Whereas in the Nakayasu synthetic unit hydrograph method, the peak time (Tp) is obtained at 1.47 hours, with a return period flood discharge of 5 – 50 years reaching 360.526 – 986.535 m³/s.

Lusi is one of the big rivers of Serang Lusi Juana (Seluna) River System that contributes to flood event on the downstream part of the system. To cope with the flood problem occurred in Seluna River System. Kedungombo Dam has been constructed on the upstream part of Serang River. However, flood flow from Lusi River, which covers 2.100 km2 of catchment area, cannot be controlled. By calculating the Lusi River design flood discharge, the flood discharge contribution of Lusi River to the Seluna River System can be predicted. Design flood hydrograph of Lusi River is determined using the synthetic unit hydrograph approach due to inadequate data. The synthetic unit hydrograph of Gama I is used in this study. To distribute design daily rainfall into hourly rainfall units to be applied in flood hydrograph calculation, hypothetic rainfall distribution is used by employing the Alternating Block Method (ABM) and Tadashi Tanimoto methods for several floods returning period. Design flood discharge applied for the calculation is the results of the ABM Rainfall distribution based on the two-daily rainfall data. The results of design flood discharge under this method show 748m3/s for return period of 2 years, 1036m3/s for return period of 50 years, 1097 m3/s for return period of 100 years and 1158 m3/s for return period of 200 years. 96% of Lusi River design flood gives contribution to the Seluna River System which is approximately 1200m3/s gained from Q200 design flood discharge in Klambu barrage Key Words : Flood discharge, synthetic unit hydrograph, hypothetical rainfall distribution, design discharge.

Flooding refers to the adverse effects caused by rivers overflowing their banks due to various reasons, affecting surrounding land, residential areas, and infrastructure. At the watershed scale, particularly in cases where flow monitoring stations are absent, hydrographs must be generated to analyze rainfall-runoff relationships for flood assessments. This study aims to generate synthetic hydrographs, analyze rainfall-runoff relationships, and estimate flood discharges for different return periods in a predominantly forested sub-watershed located in the Sarıyer district of Istanbul. The study analyzed extreme rainfall by calculating 24-hour maximum values for return periods of 2 to 100 years using four common probability distribution functions: Normal, Log-Normal, Log-Pearson Type III, and Gumbel. Among these methods, Log-Pearson Type III yielded higher rainfall values, and given the extreme nature of floods, it was preferred for discharge calculations. In the second stage of the study, flood hydrographs specific to the watershed were generated for different return periods using the DSI, Mockus, and Snyder unit hydrograph methods, incorporating watershed physical characteristics and dimensionless unit hydrograph coordinates. The results indicated that the DSI and Mockus methods produced similar and higher peak discharge values (Qₘₐₓ = 67.44 and 63.76 m³/s, T=100 years), whereas the Snyder method resulted in lower peak discharge (Qₘₐₓ = 32.17 m³/s for T = 100 years) but a longer hydrograph duration. Overall, it was concluded that the DSI and Mockus methods are more suitable for flood analysis in forested and relatively small watersheds (≈10 km²) due to their effectiveness in generating hydrographs for flood assessments. This study contributes to the literature by offering a comparative evaluation of three widely used synthetic unit hydrograph methods, specifically tailored for a forest-dominated ungauged basin in an urbanizing region of Istanbul, providing actionable insights for flood estimation in data-scarce, forested urban catchments.

In the urban area, flooding becomes the most common disaster that has not been resolved until today. The utilization of river border area into housing and lack of absorption area becomes the trigger factor of urban flooding, as what is happening around Way Halim River on Seroja street. In this area, floods often happen during the rainy season, with the latest events recorded on January 21st, 2021. Analysis of flood intensities and discharges can be parameters for the decision-making of flood mitigation strategies. This study aims to analyze the flood discharges along Way Halim River, Seroja street by comparing the flood discharges resulting from three analysis methods of Synthetic Unit Hydrograph (SUH) including Gama I SUH, Nakayasu SUH, and Snyder SUH. Finally, suitable flood mitigation strategies were also proposed in this study based on the flood discharges and rain intensities. The results showed that Nakayasu SUH had the highest peak flood discharge than Snyder SUH and Gama I SUH. Based on the results of the investigation of land suitability; and analysis of rainfall intensities and flood discharges, the proposed flood mitigation in Seroja street is by installing biopore infiltration holes along Seroja street for storing water and reducing the risk of flooding in the area.

This research is motivated by the natural flooding disaster in the Landak sub-watershed area, which can be caused by river overflow due to high rain intensity. Flood discharge can be calculated using the Synthetic Unit Hydrograph method if the available data is limited, such as only obtaining rainfall data and watershed characteristics.Several Synthetic Unit Hydrograph (SUH) methodologies, including SUH Snyder, Nakayasu, Soil Conservation Services (SCS), Gama I, ITB, and Limantara, were utilized in this study. The analyzed data included precipitation data and measured discharge data. Rainfall data are analyzed using the homogeneity test, statistical descriptors, and chi-squared to determine the planned flood discharge. Then, continue with the study of rainfall frequency and analysis of rainfall intensity so that the maximal discharge can be analyzed using three SUH methods: HSS Snyder, Nakayasu, and SCS. The analysis of measured release is conducted by statistically analyzing estimated discharge data.The analysis results are then compared to obtain the percentage error between the discharge plan and the minimum measured discharge. The results showed that the HSS Snyder method was selected for analyzing flood discharge in the Landak sub-watershed basin because it has the minimum percentage error from comparing planned release and measured discharge values. Therefore, for the calculation of flood discharge analysis of the Landak sub-watershed basin, the HSS Snyder method is used with the acquisition of flood discharge plans for the return period of 2, 5, 10, 20, 50, and 100 years of 648,880 m3/sec, 896,335 m3/sec, 1025,954 m3/sec, 1132,006 m3/sec, 1252,788 m3/sec, 1335,273 m3/sec.

Elements of hydrographs such as peak rate and time to peak are essential in the planning and design of hydraulic structures. Not two hydrographs are identical as not two watersheds and rainfall characteristics are identical. This calls for the development of hydrographs for every watershed. However, there are few number of gauged streams as the installation and management costs are expensive . Many models have been developed to overcome these problems, but these methods have not been widely used for they require lots of input parameters. As a result, a number of synthetic unit hydrograph (SUH) methods have been proposed as means of developing hydrographs for ungauged watersheds . However, their performance is not a much studied subject. This research was initiated to investigate the performance of Snyder’s, Soil Conservation Service, Mockus, Nakayasu, Rodriguez-Valdez, and Gupta-Waymire SUH methods at Guvenc micro-watershed in Turkey. Global Mapper was used to download Digital Elevation Model (DEM), and Watershed Management System (WMS) software was used to manipulate the DEM and generate necessary data in accordance with the requirements of each SUH method. The peak discharge and the time to peak were used to compare the observed unit hydrograph (UH) with the SUHs. The results of the study showed that data from internet sources could be used as a source to generate appropriate watershed characteristics necessary to derive SUH. The comparison of the elements of SUHs showed that the SCS approach performed best in simulating the peak runoff in the study area.

A dam is one of the water structures that have many benefits for humans. However, flood disasters caused by dam break may have a very bad impact on human life. This study specifically analyzed the impact of flooding caused by the failure of the Karalloe dam in Bone Regency, South Sulawesi Province, Indonesia. For the first time, the selected flood discharge used in the dam break analysis was verified using the Creager graph by comparing the calculated discharge from several synthetic unit hydrograph methods (HSS) with the flood discharge measured on the automatic water level recorder (AWLR) at the monitoring point. The impact of flooding due to dam break was simulated using HEC-RAS 2D combined with ArcGIS for mapping. The calculation results of the design flood discharge based on rainfall data using the methods of HSS Nakayasu, HSS ITB I, HSS ITB II, and HSS SCS (HEC-HMS) as well as the calculation of the designed flood discharge based on the discharge data showed that the design flood discharge value which is closest to the measured discharge value and Q1000 Creager was the HSS SCS method. The flood discharge values obtained based on the HSS SCS method for Tr (return period) 2 years, Tr 5 years, Tr 10 years, Tr 20 years, Tr 25 years, Tr 50 years, Tr 100 years, and Tr 1000 years were 322.70 m³/s, 464.10 m³/s, 560.40 m³/s, 658.40 m³/s, 682.70 m³/s, 787.00 m³/s, 885.70 m³/s, and 1202.60 m³/s, respectively. The simulation results showed that 22 villages will be affected by flooding due to the failure of the Karalloe dam and the fastest standby time of the flood is 12 minutes, namely at Lookout Point 7 in Paitana Village. This result suggests that early warning system should be installed at the downstream of the dam and flood disaster mitigation should be adopted and applied to these threatened area.

The present study critically reviews the synthetic unit hydrograph (SUH) methods available in hydrologic lit- erature. The study reveals that the traditional methods of SUH derivation, e.g., Snyder, SCS, traditional methods like Sny- der and TS method that does not yield satisfactory results, and their application to the practical engineering problems is tedious and combursome. On the other hand, probability distribution functions (pdfs) based SUH methods are easy to ap- ply, and easily meet the UH criterion, i.e. the area under the curve is unity, and rely on a stronger mathematical base and sounder hydrologic perception. The recent pdfs used for deriving UHs in ungauged catchments, address the SUH shapes with more flexibility than the earlier pdfs proposed by (1) for SUH derivation.

This study aims to assess various empirical synthetic unit hydrograph (SUH) methods and find the best method. Ideally, each river should have a definite rain gauge station (RGS) to get sufficient rainfall data that is available for carrying out meaningful analysis. The provisions of Indian Standard (IS) 4987:1994 determined the optimum number of RGS. In the absence of RGS, the SUH is recommended. SUHs have been developed using various methods such as Snyder's, Taylor and Schwarz, Soil Conservation Service, Mitchell's and Central Water Commission (CWC). In the present study, the Rel River Basin (RRB) is considered as the study area which has two existing RGS. IS 4987:1994 suggested that four RGS are required for more reliable rainfall data. Various efficiency criteria such as Correlation Coefficient, Pearson Coefficient, Nash Sutcliffe Efficiency, Index of Agreement, Normalized Root Mean Square Error, Mean Absolute Error, Root Mean Square Error and Kling-Gupta Efficiency have been used to compare SUH methods. The ranking of SUH methods was reported based on the compound factor (CF) through efficiency criteria. The 1.125 CF was observed as the minimum for the CWC method and recommended for determining peak discharge and timing for the study area.

This paper compares the results of direct runoff obtained by a numerical model of the shallow water equations (SWE) with the synthetic unit hydrograph (SUH) methods generally used in Indonesia. It is known that such SUH methods are still empirical, thus making it difficult for users to determine a representative method. Meanwhile, the hydrodynamic approach such as the SWE numerical model can achieve more accurate results in predicting the direct runoff compared to the SUH methods, because the model itself is derived mathematically based on the physical processes. The findings indicate that the direct runoff predicted using the SWE numerical model (HEC-RAS 5.0.7) produced more accurate results for the peak discharge with an average error of -0.07%, the peak time with an average error of 19.77%, and the shape of the hydrograph with the smallest Root Mean Square Error (RMSE) from all the cases tested. Therefore, it can be concluded that in the future the use of a hydrodynamic approach is highly recommended for the direct runoff prediction. This paper was also aimed to be used as a reference in the development of new, more accurate SUH method in the future.

Abstract: Various kinds of buildings in civil engineering require careful planning. For example, in the planning of a water building needed a method to calculate the design flood discharge before starting to plan the dimensions of the building to meet the effectiveness of the water structure. Design flood discharge can be determined using several hydrograph methods that have been used in water building planning in Indonesia. One of the popular hydrograph method used is the Nakayasu Synthetic Unit Hydrograph method. In this case, the design flood discharge is located in the Garang watershed, precisely in Semarang City, province of Central Java, using rainfall data for the past 16 years. Hydrological analysis is carried out first before determining the design flood discharge with a return period of 2, 5, 10, 25, and 50 years. The results of the design flood discharge using Nakayasu method respectively were 305,522 m3/s, 390,742 m3/s, 447,783 m3/s, 520,560 m3/s, and 574,912 m3/s.

In this study, an Artificial Viscosity (AV) technique was developed for direct runoff calculation, instead of using the conventional Synthetic Unit Hydrograph (SUH) methods. We solved the Shallow Water Equations (SWE) with second-order accurate Godunov finite volume model and fourth-order Runge-Kutta explicit scheme. The AV technique was devised with a Laplacian and a biharmonic operator, and employed to solve the convective terms of the SWE. This technique was applied to rainfall-runoff laboratory cases with the measured rainfall and observed direct runoff values. For comparison purpose, several SUH methods commonly used such as SCS, Snyder, GAMA-1, ITB-1, ITB-2, and Nakayasu, were also used to compute the direct runoff values. The results showed that the AV technique could predict three parameters (i.e., peak discharge, time-to-peak, and shape of the direct runoff hydrograph) accurately. Meanwhile, significant discrepancies were shown by the SUH methods in estimating such parameters, thus indicating that the SWE modeling with an AV technique is significantly more accurate than the SUH methods in predicting the direct runoff hydrograph. This study shows an interesting example of how modern numerical computations can improve the runoff prediction and may be included as a standard technique for runoff computation in the future.

Floods often occur in several regions in Indonesia. The problem is the flooding with its uncertain characteristics is one of the environmental problems that has not been handled optimally. The method of converting rain data into discharge data for flood analysis has been widely presented in previous studies. The methods used to analyze flood discharge also vary, starting from rational, empirical, statistical models to the unit hydrograph model. This research aims to determine the flood discharge design for return periods 2, 5, 10, 20, 25, 50, and 100 years in Tojo watershed, Tojo Una-una Regency using the synthetic unit hydrograph method of ITB-1. Research methods are data collection and data analysis. Data collection was carried out at several agencies and collecting from online sources. Results of this research design flood discharge that was analyzed by synthetic unit hydrograph of ITB-1 method. The maximum design flood discharge at Tojo watershed are 82.375m3/s for a 2-year, 98.21 m3/s for a 5-year, 104.77 m3/s for a 10-year, 111.83 m3/s for a 20-year, 113.3 m3/s for a 25-year, 118.87 m3/s for a 50-year, 123.86 m3/s for a 100-year return period