Synthetic Unit Hydrograph Research Articles

Avoiding Flood by Improving Cross-Sectional Capacity through River Normalization

Bekasi is one of the regions in Indonesia that often suffer from flooding. To overcome flooding problems in the Bekasi area, the Ciliwung Cisadane River Basin Center has begun a normalization project along the Bekasi River. This research aimed to evaluate the Bekasi River's cross-sectional capacity both before and after normalization. The analysis focused on the section where the Cileungsi and Cikeas rivers converge to the Bekasi weir. In this research, secondary data were employed, such as national digital elevation model data, detailed engineering designs of Bekasi River flood control activities, and rainfall data from the Cibinong Station that covers the period from 2006 to 2020. The result from planned flood discharge with the Nakayasu synthetic unit hydrograph method for a return period of 25 years on the Bekasi River was obtained at 665.81 m3/s. The results of hydraulic analysis before normalization with the HEC-RAS application show that flooding occurred at 102 out of 116 stations, with capacities of river cross-sections ranging from 453.49 m³/s to 665.71 m³/s at these overflow stations. Following the river normalization process, the cross-sectional capacity at all Bekasi River stations can accommodate flood discharge without any instances of overflow.Keywords: Flood, HEC-RAS, Nakayasu, Normalization, Rainfall.

Effect of Flow Discharge on Sedimentation in Paneki River

Introduction: Paneki River has the potential for sedimentation caused by flow discharge. The condition of the river is getting wider every day which will threaten the risk of flooding if there is heavy rain with high intensity. The purpose of this study is to determine the return time flood discharge and basic sediment transport discharge in the Paneki river which can be used as a reference in planning sediment control buildings. Method: This research method includes primary data collection and secondary data collection, data management including calculating width, slope, design rainfall, design flood discharge, sieve analysis, and specific gravity. Then proceed to calculate the return time flood discharge using the Nakayasu synthetic unit hydrograph method and basic sediment transport using the Meyer-Peter and Muller method. Results and Discussion: From this research, the result of the 2-year return time flood discharge is 121.306 m3/det, for 5-year return time flood discharge is 185.069 m3 /det, for 10-year return time flood discharge is 209.261 m3 /det, for 25-year return time flood discharge is 312.359 m3 /det, and for 50-year return time flood discharge is 373.566 m3 /det. The results of basic sediment transport discharge per cross-section ranged from 0.0000861 m3 /det to 0.005641775 m3 /det. Conclusion: The study shows that sedimentation is influenced by flow discharge. The results of the calculation of flow discharge (Q) and bottom sediment transport (Qs) in Paneki River using the Meyer-Peter and Muller method resulted in Qs varying from 0.0000861 m³/det to 0.016551197 m³/det, according to the measured flow discharge. The greater the flow discharge, the greater the sediment transport, indicating a direct relationship between flow discharge and sedimentation.

Analisis Kapasitas Efektif Tampungan Kali Pancir

Kali Pancir is one of the rivers in Jombang Regency which often experiences flooding. The cause was heavy rain and the critical condition of the embankments. In this research, flood discharge analysis was carried out using synthetic hydrographs and hydraulic modeling for river flow. The data needed is rain data from rain stations around the Pancir River and river profiles. The method used to calculate flood discharge is the Nakayasu Synthetic Unit Hydrograph for 6 different return periods. Simulation using HEC-RAS software is used to simulate flow profiles to determine river cross-sections that are critical to flooding. Based on the results of the calculation analysis, it was found that the peak flood discharge occurred at 3.5 hours. The greater the return period, the greater the river cross section that experiences overflow. At a return period of 1.01 years, the critical cross section starts at STA 45, while at a return period of 50 years, the critical cross section occurs starting at STA 6.

Estimation of Catchment Parameters of Snyder's Synthetic Method for Water Resources Planning and Flood Management in Sri Lanka

Snyder's synthetic unit hydrograph method is widely recognized for synthesizing unit hydrographs. This paper illustrates a study demonstrating how to estimate catchment parameters using Snyder's synthetic method for hydro-meteorological stations maintained by the Irrigation Department and its application to Sri Lanka. Updated Snyder's Unit Hydrograph parameters, including coefficient accounting for flood wave and storage condition (Cp) and coefficient representing variations of catchment slop and storage (Ct) for 15 river gauge stations spread across the island, have been presented in this paper. The Cp values vary from 0.22 to 0.7, and the Ct values vary from 0.48 to 5.76. Updating the Snyder parameters is a long-term requirement, and these values can be used to update the previous values estimated in 1980.

Estimation of Synthetic Unit Hydrographs’ Parameter Values: The Case of Wadi Al-Badan Sub-Catchment, West Bank, Palestine

Developing unit hydrographs is critical in gauged catchments. Due to the lack of local data, engineers should strive to estimate discharges based on empirical (synthetic) methods in ungauged catchments. Synthetic unit hydrograph methods, such as the Snyder and Soil Conservation Service are popular and play an essential role in hydrology. These methods are simple, requiring only catchment characteristics. Therefore, these methods are valuable tools for simulating runoff in ungauged catchments. This research paper focuses on the Al-Badan sub-catchment, which is located in the northeastern part of the West Bank in Palestine with an area of 83 km2. The study used a de-convolution matrix approach to develop an average one-hour unit hydrograph by selecting four significant rainfall events in the period (2005-2007), and the direct runoff hydrographs which are measured by Al-Badan flume located in the outlet of the sub-catchment. By computing the characteristics of the average one-hour UH with a peak discharge of 4.52 m3/sec and time to peak of 5 hours, Snyder and SCS UHs were developed to suit Al-Badan sub-catchment physical characteristics. The parameters were determined for the Snyder; peaking coefficient depends on the storage capacity of the catchment Cp = 0.88 and the non-dimensional regional coefficient representing catchment storage effects and slope Ct = 1.26 and for the SCS; Cp = 1.90 and the coefficient depending on the total runoff volume occur before peak discharge C = 2.92. These synthetic one-hour UHs were examined for two selected rainfall events that occurred in the period (2017–2019) by comparing observed and simulated direct runoff hydrographs. The performance was tested statistically. Results showed that the synthetic UHs are suitable for application and that the SCS method is more applicable.

Hydrological Modelling with HEC-HMS in Krueng Peudada Sub-Watershed Bireuen Regency

The flood that occurred in Krueng Peudada was influenced by several factors, such as watershed conditions. Heavy rains caused Krueng Peudada to overflow so that a number of villages adjacent to the river were submerged. Based on these problems, to minimize the occurrence of flooding in Krueng Peudada building, namely by carrying out occurrence of flooding in Krueng Peudada to be used to obtain peak discharge as a reference in building planning in Krueng Peudada using HEC-HMS (Hydrologic Engineering Center’s Hydrologic Modelling System). The benefit of the research is that the resulting model can be useful as a guide in calculating flood discharge considerations. The scope of this research includes the research location at Krueng Peudada using annual maximum daily rainfall data, calculating the return period of rainfall using of Gumbel probability distribution, Normal Log, Normal, and Pearson III Log as the basis for calculating the discharge and continuing the calculation of the hours with Manonobe and ABM. The results of calculations of the Nakayasu Synthetic Unit Hydrograph Method and running from HEC-HMS found that the flow that occurred in the Krueng Peudada two sub-watershed was 2903m3/second and 2723,0 m3/second, it can be concluded that in determining watershed management the flood discharge obtainded has error as much as 6,2%. The difference in the results obtained is due to the number of sub-watersheds in the watershed based on different flows and the value of the curve number for each area of the sub-watershed.

Parameters Cp and Ct in Snyder Synthetic Unit Hydrograph Due to Land Use Changes in Napel Sub-watershed, Bengawan Watershed

The parameters Cp and Ct depend on the characteristics and slope of the watershed. Watershed characteristics include types of land use that are always dynamic over time. The slope of the watershed affects the smoothness and velocity of runoff flow. The development of an area will cause changes in land use which tend to become more impermeable, of course also affecting the smoothness and speed of runoff flow. This of course results in changes in Cp and Ct in a watershed. Changes in land use in the Napel watershed within 7 years starting from 2015 to 2021 have decreased in areas of jungle forest and other water catchment areas. This research was conducted to determine the influence of land use change on peak discharge and Cp and Ct parameters. The method used is the Snyder Synthetic Unit Hydrograph, which has been tested for suitability against the Measured Unit Hydrograph with validation results included in the very strong correlation category. The Ct value used in 2015 was 1.65 and in 2021 it was 0.78 while the Cp value used in 2015 was 1.4 and in 2021 it was 1.1. The results of the analysis using the Snyder method produced a discharge of 417.882 m3/s in 2015 and 619.52 m3/s in 2021. The resulting discharge shows a significant increase.

The best synthetic unit hydrograph for peak discharge analysis Case: The Bengawan Solo River, section Dengkeng–Pusur

The best synthetic unit hydrograph for peak discharge analysis Case: The Bengawan Solo River, section Dengkeng–Pusur

Hydrological Analysis of the Makassar-Pare Corridor Rail Elevated Bridge in Pangkep Regency South Sulawesi Province

Hydrological analysis is an important stage in the development of water resources. Determining hydrological quantities is actually not too difficult if the data for analysis purposes is available in sufficient quantity and quality. The method used for the analysis of the planned flood discharge depends on the amount of discharge data and rainfall data. Based on the analysis of discharge data and rain data. For planning the storage capacity of the river crossing the railway bridge, using the Nakayasu Synthetic Unit Hydrograph (HSS) Method, the river water level to the JEKA 2 structure is 13.38 m and the river water level to the tracks is 16.38 m so that the railroad tracks at Bridge 2 can be said to be safe against the river water level. Hydrological analysis is one part of a whole series in the planning of transportation structures such as roads, bridges and railway bridges including flood barrier embankments and so on.

Increasing surface impermeability influences peak discharge with the Snyder method in the Ngadipiro sub-watershed of the Bengawan Solo watershed

This research was conducted to determine the effect of increasing soil impermeability in the Ngadipiro Sub-watershed on Cp and Ct numbers in 2015 and 2021. The measured unit hydrograph is used as a reference in calculating the Synder synthetic unit hydrograph method. Test the validation of the two methods using the correlation coefficient. The results of this study showed an increase in tightness in the form of an increased runoff coefficient from 0.26 in 2015 to 0.34 in 2021. This increase in tightness is also in line with the increase in peak discharge using the Measured unit hydrograph in 2015 of 73.3757 m3/s and 2021 of 139.1005 m3/s. The results obtained using the Snyder method obtained peak discharges in 2015 and 2021 of 75.10 m3/s and 148.89 m3/s. The results of the correlation test between the two methods obtained very strong correlation results with a 2015 R-value of 0.96 and a 2021 R-value of 0.92. The non-physical parameters of the watershed, namely Ct and Cp, were optimal in the Ngadipiro Sub-watershed in 2015, the Ct value was 2.2 and the Cp value was 0.9, while in 2021 the Ct value obtained was 1.3 and the Cp value was 1.1.

Development of Synthetic Unit Hydrographs Using Spatial Proximity Regionalization for the Makiling Forest Reserve, Philippines

There is a dearth of streamflow data in the Philippines to generate hydrographs needed for flood forecasting and water resources assessment. A method of generating and calibrating synthetic hydrographs using model simulations and spatial proximity regionalization is presented. Synthetic unit hydrographs of four storm events in the gauged watershed of Makiling Forest Reserve were generated using Soil Conservation Service Unit Hydrograph, Clark Unit Hydrograph, and Snyder’s Unit Hydrograph methods. The generated synthetic hydrographs for each runoff modeling technique were calibrated with the actual hydrographs of the watershed. Snyder’s Unit Hydrograph model results were the most acceptable based on the Nash-Sutcliffe Efficiency, Index of Volumetric Fit, and Relative Error of Peak Flow. The weighted values of the calibrated watershed parameters computed using spatial proximity regionalization technique and the hyetographs derived from the Rainfall Intensity Duration Frequency Curve of the University of the Philippines Los Baños-National Agrometeorological Station were used to generate the synthetic unit hydrographs for three neighboring ungauged watersheds at 2-, 5-, 10-, 15-, 20-, 25-, 50, 100-year return periods. Total runoff volume, the magnitude of peak flows, and time to peak derived from the generated hydrographs can be used in watershed planning, water resources management, flood forecasting and the design of various water control structures.

Flood Model of Downstream Kali Lahar Using HECRAS

Flooding that occurs in the area around Kali Lahar is a problem that always occurs when the rainy season. This research aims to find the causes of flooding in Kali Lahar, located on Jalan Letjen Sutoyo, Malang City, by considering the hydrological conditions in the Kali Lahar subwatershed. The data used in the analysis is rain data from the Sukun, Ciliwung, and Petungsewu stations, with the same data range between 2008 and 2020. There is also spatial data such as DEMNAS and river networks. The analysis is carried out by modeling floods with synthetic unit hydrographs, which are then modeled with HEC-RAS 1D and 2D software to determine whether the river can accommodate flood discharge with a return period of 10 years. The discharge produced by Unit Hydrograph Nakayasu was 134.25 m3/s. This discharge is modeled using HECRAS and produces water levels up to 1.5 m above the banks. Increasing the depth of the channel is an alternative solution for flooding in this area. The simulation results of the new dimension show no flooding in the area around the channel. The results of this research can contribute to the planning and arrangement of existing canals in Malang City so that they can prevent or reduce flooding that occurs.

Selecting the accurate hydrological method for estimating peak discharge in the Lesti River Catchment Area, Malang Regency, East Java Province, Indonesia

Estimating peak discharge in the catchment poses a challenge for hydrologists due to the potential overflow risks. The present study examined various methods, including Synthetic unit hydrograph, Melchior, and Rational, to determine the peak discharge value in the Lesti River Catchment Area. Accurate hydrological input data is essential for effectively estimating peak discharge and mitigating potential damage or failure. Optimized physical parameters using geographic information systems are critical in generating peak discharge values, emphasizing their importance in the estimation process. The mean absolute percentage error (MAPE) and mean average error (MAE) were used to determine the accurate method for estimating peak discharge. Analysis results showed varied peak discharge values across different methods, and it found that the MAPE values ranged from 15.15% to 7.48% and the MAE values ranged from 1.47% to 0.63%, respectively. The Nakayasu synthetic unit hydrograph obtained the minimum error measure value compared to other methods by 7.48% in MAPE and 0.63% in MAE. Therefore, the MAPE and MAE performance considered that the Nakayasu was closely approximating the observed peak discharge and a relatively accurate method for estimating peak discharge in the Lesti River catchment area.

ANALISIS BANJIR SUNGAI MENGGUNAKAN MODEL HEC-RAS DI WILAYAH DAS TABANIO KABUPATEN TANAH LAUT PROVINSI KALIMANTAN SELATAN

This study aims to determine the amount of water runoff and water depth in the Tabanio Watershed, Tanah Laut Regency. The study was conducted using the HEC-RAS software to generate a flood simulation model. Data analysis included Digital Elevation Model for National Scale (DEMNAS) data, flood discharge data, rainfall data, river bathymetry, and tidal data. DEMNAS data was obtained from the website of the National Geospatial Information Agency (BIG), rainfall data was obtained from the Center for Hydrometeorology and Remote Sensing (CHRS) website. Rainfall data analysis involves selecting the maximum daily rainfall value to determine the flood discharge. The hourly flood discharge is calculated using the Synthetic Unit Hydrograph method with the Nakayasu approach. River bathymetry data is processed as additional data for DEM, with interval recording done every 0.2 seconds. Tide data was obtained through prediction based on the location constant closest to the research area and analyzed using the Pasut.exe software for a period of 6 days. Based on the results of flood analysis research using the HEC-RAS model in the Tabanio Watershed, Tanah Laut Regency, South Kalimantan Province, it can be concluded that the model results show the water depth and area of water runoff at maximum discharge. as follows: less than 0.5 meters with a very low category covering an area of 4,168.86 hectares, 0.51 to 1.5 meters with a low category covering an area of 6,417.79 hectares, 1.51 to 2.5 meters with a medium category covering an area of 1,987, 25 hectares, 2.51 to 3.5 meters with a high category of 741.47 hectares, and above 3.51 meters with a very high category of 113.69 hectares. So that the total water runoff reaches 13,429.05 hectares.

PREDICTION OF RUNOFF BY SYNTHETIC UNIT HYDROGRAPH METHODS FOR THE DESIGN STORMS IN WARANA RIVER BASIN, MAHARASHTRA, INDIA

The authors' goal was to calculate average representative unit hydrographs (UHs) from a few isolated storms for the upper Warana River basin in Maharashtra, India. Based on the approaches used by Snyder, the Soil Conservation Service (SCS), the Central Water Commission (CWC), and Common, synthetic unit hydrographs were created. This study was utilised to choose appropriate correlation coefficients for Synthetic Unit Hydrograph (SUH) evaluation for the ungauged basins with identical hydrological conditions. The outcomes were then analyzed with those attained using other techniques and with the actual UH. In order to calibrate and validate the effectiveness of Snyder's model, the authors employed it on the sub-basins of the Warana river basin. The hydrograph's shape resembled the observed UH produced by the other methods, according to the results, and the peak discharge calculated using Snyder's technique had the lowest percentage error (0.26%)

A comparative assessment and geospatial simulation of three hydrological models in urban basins

Abstract The risk of flooding is a destructive natural hazard, and it is increasing due to heavy rainfall and anthropogenic factors. Hydrologic–hydraulic models serve as valuable tools for flood forecasting and predicting future flow patterns. These models evaluate and simplify processes in ungauged basins. In this study, three hydrologic models (soil conservation service [SCS], Snyder, and Temez) were used to calculate synthetic unit hydrographs for the Humaya and Tamazula River (H-T-R) basin. Additionally, the flows derived from the three models were simulated in Hydrological Engineering Center River Analysis System for various return periods (2, 5, 10, 25, 50, and 100 years). The accuracy of the models SCS, Snyder, and Temez was evaluated using the root-mean-square error (1162.44, 144.76, and 2890.6); Nash–Sutcliffe efficiency (−51.12, 0.19, and −312.28); R 2 (0.97, 0.94, and 0.94), and kappa index (0.8534, 0.9895, and 0.7155), respectively. The data used in this study were obtained from a hydrometric station located on the Culiacan River. The main findings indicate that the Snyder model demonstrated a better predictive capability compared to the Temez and SCS models, albeit with a tendency to overestimate. Simulated flood depths are deeper in the upstream areas, particularly upstream from the Musala Island bifurcation on the Tamazula River, with values of 11.82 m for SCS, 9.76 m for Snyder, and 13.5 m for Temez. The simulation revealed potential overflow zones along the Tamazula River, particularly at the channel bifurcation and near the confluence with the Humaya River, during the 100 year return period simulation.

Prediction of Snyder Synthetic Unit Hydrograph Coefficient for Cidurian Watershed

Prediction of Snyder Synthetic Unit Hydrograph Coefficient for Cidurian Watershed

Pemodelan Genangan Banjir Sub DAS Bengkulu Hilir Provinsi Bengkulu Menggunakan Program Hec-Ras 5.0.7 Berbasis Ras Mapper dan Arc-Gis 10.8

The Down Stream Air Bengkulu Watershed is part of the Air Bengkulu Watershed in Bengkulu Province. Flooding in this area frequently leads to major subdistrict, economy, and environmental impacts. The aim of the research is to develop a flood forecasting model that is capable of mapping potential flood areas in order to support flood control efforts. The method used is a hybrid model between a hydrological model, a hydraulics model and a Geographic Information System (GIS). The hydrological model is input to HEC-RAS software, It’s developed based on Snyder's Synthetic Unit Hydrograph (SUH). The hydraulics model was prepared using the software of HEC-RAS version 5.0.7 and the it’s output was used as material for preparing potential flood inundation maps. The potential flood inundation map was prepared by overlay method with the help of the Arc-GIS version 10.8 application. The research results show that the peak flood time is 7.43 hours with peak discharge for a 100 year return period of 1,542 m3/second. Flood inundation occurred in nine sub-Districts including Talang Empat District (552,819 ha), Karang Tinggi (391,648 ha), Selebar (24,118 ha), Singaranpati (95,806 ha), Ratu Samban (6,838 ha), Ratu Agung (212,173 ha), Sungaiserut (541,659 ha), Muara Bangkahulu (395,495 ha), and Pondok Kubang (197,167 ha). The conclusion of the research is that the model developed is able to answer peak times, area and water level of inundation as well as potential locations that will be flooded.

Analisis Banjir Metode Hidrograf Satuan Sintetis SCS dan Nakayasu DAS Pesung, Batam

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.

Development of the Synthetic Unit Hydrograph Tool – SUnHyT

Unit hydrographs (UH) are widely used in scientific research and engineering projects to simulate rainfall-runoff processes. There are four main approaches for calculating UH: the traditional, the conceptual, the probabilistic, and the geomorphological approaches. Most software designed to facilitate the estimation of UH is usually based on only one UH approach, limiting its applicability for scientific hypotheses testing. This paper presents the Synthetic Unit Hydrograph Tool (SUnHyT), which provides nine different UH models from the four main approaches used in UH applications. SUnHyT is an open-source application that can be used intuitively through a graphical user interface. We tested the model in a case study that highlights the need for alternative approaches of UH when the traditional approach does not perform well. SUnHyT allows the estimation of design hydrographs in gauged and ungauged catchments and can be useful for hydrologists, water managers and decision-makers.