I Gede Tunas - Academia.edu (original) (raw)

Papers by I Gede Tunas

Short-cut is one offlood control technique in meandering river especially in downstream reach. In... more Short-cut is one offlood control technique in meandering river especially in downstream reach. In some cases, this technique is still used although in eco-hydraulic concept, it is less effective and on the contrary, it causes bigger flood on downstream river. This research is to know the effect of short-cut on flood characteristic by using DonginRiver in Banggai Regency as model.This research is conducted with hydrology analysis to the rainfall and watershed data to set flood hydrograph as upstream boundary condition. The simulation deals with flood routing by using HEC-RAS hydrodynamic models to know the hydrograph, water surface, velocity and energy line along the river reach. To obtain the optimal parameter value, formerly, HEC-RAS must be calibrated by adjusting simulated water surface with observed water surface in a cross section.The result of simulation using annual discharge (Q1=123.54 m3/s) showed that the short-cut affect the flood characteristic and water surface profile....

Terdapat dua prosedur yang dapat digunakan untuk memperkirakan laju erosi dengan menggunakan meto... more Terdapat dua prosedur yang dapat digunakan untuk memperkirakan laju erosi dengan menggunakan metode USLE berdasarkan data historis (historical data) pada masa yang lampau. Cara pertama yakni dengan menganalisis laju erosi rata-rata bulanan untuk seluruh tahun data sekaligus. Keluaran dari cara ini adalah perkiraan laju erosi rata-rata bulanan. Cara yang kedua yakni dengan melakukan perhitungan laju erosi rata-rata bulanan untuk setiap tahun data. Perbedaan prosedur dalam memperkirakan laju erosi tersebut, memungkinkan terjadinya perbedaan angka laju erosi yang akan dinyatakan dengan angka nisbah pengangkutan sedimen (sediment delivery ratio, SDR). Penelitian ini mengkaji pengaruh kedua prosedur perkiraan laju erosi tersebut terhadap konsistensi nisbah pengangkutan sedimen. Hasil penelitian yang diterapkan pada sub-DAS Miu dan Wuno di Palu-Sulawesi Tengah menunjukkan bahwa angka nisbah pengangkutan sedimen (SDR) kedua prosedur tidak menunjukkan perbedaan yang besar, masing-masing seb...

2018 2nd Borneo International Conference on Applied Mathematics and Engineering (BICAME), 2018

ITS-2 is a synthetic unit hydrograph (SUH) model developed at the Institut Teknologi Sepuluh Nope... more ITS-2 is a synthetic unit hydrograph (SUH) model developed at the Institut Teknologi Sepuluh Nopember (ITS) in 2017. The development of this model is intended to predict the potency of flood peak based on certain rainfall inputs in the watershed system, especially in an unmeasured watershed or measured watersheds with insufficient data. The high deviation that resulted from previous similar models had low performance in the tested watershed, also the reason this SUH model was developed. The main properties of this model are the accommodation of fractal parameters of the watershed, especially in peak time equations and a very simple single curve equation derived from the two-parameter Gamma Distribution. This paper intends to introduce the ITS-2 Model to estimate flood hydrographs in various watersheds in Indonesia. By introducing this model, it is expected to be able to obtain information from various users in Indonesia regarding the performance and validity of the model, so that im...

DEStech Transactions on Engineering and Technology Research, Oct 17, 2017

The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall int... more The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall into run off for water resources development. The typical feature of this model is that the main equation represents the shape of the curve expressed by the relationship between time and discharge. In addition, the SUH model is also expressed in three parameters i.e. peak time (TP), peak discharge (QP), and base time (TB), representing the hydrograph curve equation. In general, SUH model is developed based on morphometry parameters of watershed, especially watershed area (A), main river length (L) and main river slope (S). Another approach in hydrograph modelling is based on the fractal characteristics of watershed. This study aims to develop a synthetic unit hydrograph model based on a combination of morphometry and fractal characteristics of watersheds. The three model parameters (TP, QP and TB) were predicted using multiple linear regression and compared with multiple nonlinear regression. The results of the analysis show that the two methods showed excellent performance. The estimation of SUH parameters using linear regression resulted peak time equation (TP) as function of river length (L), ratio of river length (RL) and density of drainage network (D) with determination coefficient of 99.8%, a base time equation (TB) as the function of watershed area (A) and river slope (S) with determination coefficient of 98.2%. Using multiple non linear regression, estimation of SUH parameters formulated peak time equation (TP) as function of river length (L), ratio of river length (RL) and ratio of watershed area (RA) with determination coefficient of 99.9%, a base time equation (TB) as the function of watershed area (A) and ratio of watershed area (RA) with determination coefficient of 97.9%. Peak discharge equation (QP) is stated as a function of peak time and a simple single curve equation derived from Gamma Distribution Equation.

Until today, the development of synthetic unit hydrograph model is still based on morphometry ch... more Until today, the development of synthetic unit hydrograph model is still based on morphometry characteristic of watershed or combine with other parameters. According to Sri Harto (1985), There are at least four main characteristic morphometry of watershed which highly influenced to the hydrograph and can be easily quantified namely watershed area (A), main river length (L), main river slope (S) and form factor (FB). This research aim is to analyze and verify these four factors and it's effect to the three of hydrograph parameters i.e. peak time (TP), peak flow (QP) and base time (TB). This research was carried out in eight watersheds in Central Sulawesi Province  Indonesia as the base of variable preparation to develop synthetic unit hydrograph model. Main morphometry analysis of watershed was conducted by using geographical information system (GIS) software, referring to Indonesia Topographic Map (RBI) data combined with Digital Elevation Model-Shuttle Radar Topographic Missi...

Smartek, Apr 25, 2012

A part of sediment deposition in estuary of Bengkulu River was approximately originated from Beng... more A part of sediment deposition in estuary of Bengkulu River was approximately originated from Bengkulu Watershed. The change of land use on watershed also approximately affected the rate of sheet erosion. To predict the rate of sheet erosion on Bengkulu Watershed, this research was conducted by using USLE methods and GIS. The results of this research show that the rate of sheet erosion of Bengkulu Watershed is 40.64 ton/ha/year or 2.258 mm/year. This rate is included in the 2 nd class of erosion risk (light risk) based on USDA classification (15-60 ton/ha/year). It explains that the sheet erosion on watershed give a little effect on sedimentation process in estuary. Abstrak Sebagian endapan sedimen di muara Sungai Bengkulu diperkirakan berasal dari erosi permukaan di DAS. Alih fungsi lahan (land use) di DAS juga diperkirakan telah mempengaruhi laju erosi permukaan. Untuk memprediksi laju erosi permukaan DAS Bengkulu, penelitian ini dilakukan dengan menggunakan metode USLE dan Sistem Informasi Geografis sebagai alat bantu analisis data berbasis digital. Hasil penelitian menunjukkan bahwa laju erosi permukaan DAS Bengkulu adalah 40.64 ton/ha/tahun. Angka ini setara dengan 2.258 mm/tahun dan termasuk dalam kelas bahaya erosi II (15-60 ton/ha/tahun)/ringan berdasarkan klasifikasi USDA. Hal ini berarti bahwa erosi permukaan DAS Bengkulu memberi kontribusi kecil terhadap sedimentasi di muara. Kata kunci: erosi permukaan, sistem informasi geografis, metode USLE * Staf Pengajar Jurusan Teknik Sipil Fakultas Teknik Universitas Tadulako, Palu

International Journal of Engineering and Technology

One of the important factors in water resources management is the determination of design flood a... more One of the important factors in water resources management is the determination of design flood associated with determining the size, capacity and age of the water resources structures to be built. Determination of design flood can be done in various ways, one of which is very popular to date is discharge prediction using synthetic unit hydrograph (SUH) approach. The use of unit hydrograph models has been widely applied in various parts of the world, especially in Indonesia, some of which are Snyder, Nakayasu, GAMA I and ITB-1. These methods are considered to have a good performance because it has to accommodate the characteristics of watersheds in a model parameter that greatly contributed to the process of rainfall-runoff transformation. However, in some cases it also provides a sizeable deviation, especially in Indonesia, considering that watersheds in Indonesia have different characteristics with watersheds in the United States where Snyder Unit Hydrograph developed. To overcome these problems, the unit hydrograph performance must be improved so that it can be used in various watersheds to obtain the smallest deviations. This research was conducted in 8 watersheds located in Central Sulawesi Province, Indonesia. This study aimed to improve the performance of Snyder Unit Hydrograph Model, covering Snyder, Nakayasu, SCS, GAMA I, ABG and ITB-1. The improvement of model performance was conducted by adjusting model parameters, in this case using Solver Tool on Microsoft Excel. Evaluation was done by the error indicator such as coefficient of Nash-Sutcliffe model efficiency (E). The study result showed that model parameter adjustment could decrease a deviation of SUH model parameter for peak discharge and average peak time up to 30% and could increase Nash-Sutcliffe Model Efficiency Coefficient (E) up to over 80%. The decrease of a deviation of SUH model parameter and the increase of E coefficient revealed that optimization using solver facility was effectively undertaken. However, not all deviations decreased but even increased significantly after optimization. It happened because the process of parameter optimization occurred simultaneously, and it was only based on a purpose function by maximizing Nash-Sutcliffe Model Efficiency Coefficient (E). The adjustment in this coefficient caused the increase or decrease of a parameter deviation of SUH Model depending on E value achieved on the optimization process. Overall, it could be declared that the decrease of a parameter deviation of SUH model was accompanied by the increase of Nash-Sutcliffe Model Efficiency Coefficient (E). Keywords : performance improvement, synthetic unit hydrograph, model parameters, flood prediction I. INTRODUCTION One of the important factors in water resources management and planning was flood discharge estimation functioned to determine optimum discharge size associated with dimension and a life of structures. The aim of optimum flood discharge estimation was to plan structures which did not have over a dimension (over estimated) implying on the big cost of structures or too small dimension (under estimated) causing a bigger risk of structure failures. One method that could be deployed to predict flood discharge was a hydrograph base. This method had been widely used either in overseas or in Indonesia as it was assumed to be able to imitate flood behavior from the beginning up to the end of the flood in a hydrograph format. Some of hydrograph bases particular a synthetic unit hydrograph commonly used in Indonesia, among others, were Snyder, Nakayasu, SCS, GAMA I, ABG and ITB-1. However, in some cases, these methods had obvious weaknesses because they could produce bigger deviation resulting in discharge size. Therefore, these method performances needed to be improved by adjusting their model parameters using optimization. Optimization was a procedure to maximize or minimize purpose function by changing a constraint function so that optimum value parameters could be determined. This study became very important as on 8 observed watersheds as objects of the study did not have a guidance used for references how to predict flood with the best performance. The best way produced from the optimization process was expected to be references for flood prediction, particularly in Central Sulawesi Province-Indonesia.

International Journal of River Basin Management

International Journal on Advanced Science, Engineering and Information Technology

Flood disaster in Palu River has repeatedly occurred with varying discharge magnitudes, especiall... more Flood disaster in Palu River has repeatedly occurred with varying discharge magnitudes, especially in the downstream segment near and around the estuary. The most recent flood occurred in July 2018 has inundated some areas of Palu City and resulted in a considerable impact on the socioeconomic life of the community in the city of Palu. Actually, flood prevention efforts have been undertaken by the Palu City Government and River Basin Board of Sulawesi III, one of which is by constructing levee combined with revetment along more than 5 km measured from the estuary to the upstream reach. The levee is made of soil material, while the revetment is a structure to protect the levee made of concrete. These structures were built on both sides of the river banks. However, the flood disaster always happens almost every year in this area. This paper intends to evaluate the performance of the flood control structure using Geographic Information System and HEC-RAS hydrodynamic model. The use of these tools provides the ease and efficiency of flood simulation along the river being modeled. The analysis results show that the bank capacity of Palu River is currently only effective for flood discharge below 550 m 3 /s, where the river bank capacity at the beginning of the levee and revetment design is approximately 550 m 3 /s, equivalent to the 25 years return period of discharge. The river bank capacity decreases due to sediment deposition on the river bed which were originated from the upstream watershed. This decline in cross-section capacity is estimated to be the cause of the flood disaster in parts of Palu City.

Journal Teknik Sipil Dan Infrastruktur, Jan 5, 2014

Journal Teknik Sipil Dan Infrastruktur, Oct 16, 2012

Bahan Kuliah Mahasiswa Magister Teknik Sipil Univ Tadulako

HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2020): Proceedings of the XXVII Conference on High-Energy Processes in Condensed Matter, dedicated to the 90th anniversary of the birth of RI Soloukhin

Land conversion in the Sausu Watershed, Sulawesi, Indonesia has been started massively since 1990... more Land conversion in the Sausu Watershed, Sulawesi, Indonesia has been started massively since 1990. During this period there have been changes in land cover from forest areas to more than 5,000 hectares of plantation land. The land conversion in the middle and upper watersheds is predicted to have triggered major floods which have resulted in large losses, especially in the downstream area as residential and agricultural land with an exposure area of more than 2,000 hectares. The flood in 1996 also has caused the collapse of the Upper Sausu Weir as a supplier of irrigation water for more than 7,000 hectares on the right and left sides of the river channel. This study was conducted to analyze the effect of land conversion in the watershed on increasing the flood peak using the ITS-2 Synthetic Unit Hydrograph Model, one of the flood peak prediction models developed at the Institut Teknologi Sepuluh Nopember in 2017. The research was preceded by data collection, especially rainfall data (daily and hourly), flow data and area conversion of forest land. Daily rainfall data were obtained from Sausu Rainfall Station with a range of 2000-2018, and hourly rainfall and discharge data were obtained from Nippon Koei Co Ltd. with a short range in 2002. The main research was carried out in two stages, namely, calibration to determine the optimal parameters of the ITS-2 Model and the application of the model for flood peak analysis. Rainfall as the input of the model can be defined as design rainfall with 50-year return periods, which are previously transformed to net rainfall. The losses due to evapotranspiration and infiltration were analyzed using Curve Number Method based on cover type and hydrologic condition of the watershed. The results of the analysis have indicated that land conversion in the watershed has increased the potential of peak flow to 16.5% when evaluated on these return period of flows. The peak of this flood does not seem to increase significantly compared to the great floods of the past. However, it must be understood that flooding can occur not only due to changes in land cover but can also occur due to various other factors such as changes in the characteristics of rainfall which leads to extreme rainfall with high intensity and long duration.

Journal of Ecological Engineering

High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province ... more High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province after the 2018 Palu Earthquake, one of them is in the Bangga River, Sigi Regency, Indonesia. It has caused massive impacts such as damaging agricultural and plantation areas and submerging public facilities and infrastructure and even causing fatalities. The flood carries a variety of materials, especially high concentration sediments which are thought to originate from eroded soils due to landslides induced by a 7.5 magnitude earthquake. These materials are eroded and transported by the flow at the upstream watershed due to heavy rainfall. This study intends to investigate the potential of landslides, factors that trigger floods and increased flooding after the earthquake. This research was conducted by investigating the landslides potency based on field surveys and interpretation of the latest satellite imagery, analyzing the characteristics of rainfall as a trigger for flooding, and predicting the flood potency as the primary impact of these two factors. Rainfall-flood transformation was simulated with the HEC-HMS Model, one of the freeware semi-distributed models commonly used in hydrological analysis. The model input is the configuration of river networks generated from the National DEM (DEMNAS), hourly rainfall during floods and other watershed parameters such as land cover, soil types and river slope. The similar simulation was also carried out on the condition of the watershed before the earthquake. Based on the results of the analysis, It can be inferred that flash floods in the Bangga River are mainly caused by heavy rainfall with long duration and landslide areas in the upper watershed triggered by the 2018 Palu Earthquake with an area of approximately 10.8 km 2. The greatest depth of rainfall as a trigger for flooding is 30.4 mm with a duration of 8 hours. The results of the study also showed that landslides in the upper watershed could increase the peak flood by 33.33% from 118.56 m 3 /s to 158.08 m 3 /s for conditions before and after the earthquake.

Journal of Ecological Engineering

Nowadays, the increasing intensity of extreme rainfall and changes in land use have triggered mas... more Nowadays, the increasing intensity of extreme rainfall and changes in land use have triggered massive floods in various regions of Indonesia. The changes in the characteristics of these two parameters cause an increase in the peak and duration of the flood over time. Peak and duration of flood estimation might be very useful for the national and local government because it is closely related to the effectiveness of prevention and mitigation plan in the future. A hydrograph-based model constitutes one approach to estimating them simultaneously. The objective of this research is to examine the application of ITS-2-a synthetic unit hydrograph (SUH) model which was developed at Sepuluh Nopember Institute of Technology (ITS) in 2017-for estimating the peak flood discharge as a basis for planning disaster mitigation programs. This study was carried out by testing the reliability of the ITS-2 Model using the Nash-Sutcliffe Efficiency (NSE) indicator by comparing the measured unit hydrograph and synthetic unit hydrograph derived using the model, optimizing the parameters of the model, and then analyzing the transformation of rainfall-flood discharge in the Gumbasa Watershed, one of the major watersheds in Central Sulawesi Province, Indonesia. This catchment is part of the Palu watershed, which is largely a tropical rainforest conservation area known as the Lore Lindu National Park. The input model is based on the design rainfall with a certain return period using the frequency analysis where the data was obtained from the rainfall stations in the study area. The results of the research showed that the performance of the ITS-2 model was still very good with the NSE above 80%. The difference in the peak discharge of these two unit hydrographs is relatively low, with a deviation below 10%. The optimal values of the ITS-2 Model parameter coefficients consisting of C 1 , C 2 , and C 3 were achieved at 1.29, 0.33 and 1.88, respectively. The results of the hydrograph analysis based on a 1-year to 100-year return period indicate that peak flood discharge ranges from 100 m 3 /sec to 550 m 3 /sec. From a series of analyses and tests that have been conducted in the previous and current research, it can be concluded that the ITS-2 Model can be applied to various watershed sizes, especially in Indonesia.

MATEC Web of Conferences

One popular technique used to reduce flood risk associated witha flood mitigation scheme, is norm... more One popular technique used to reduce flood risk associated witha flood mitigation scheme, is normalization of a river bank. This methodcan be effected done by adjusting the width of the river on the left andright banks, in order to increase channel capacity. The biggest obstaclemost often encountered in adjusting the river banks is insufficient landarea, both on the left and right sides. The capacity of the river channel cantherefore not be optimised, due to this limitation. This study intends toevaluate the effectiveness of river bank normalization to reduce flood riskin the Puna River, Central Sulawesi Province of Indonesia. The capacityevaluation was conducted under two conditions i.e. before and afternormalization of the river bank, using HEC-RAS Hydrodynamic Program, integrated with GIS. The level of effectiveness is measured by acomparison between the capacity of the river channel after banknormalization with the required channel capacity on 100 years returnperiod of discharge...

Jurnal Hidroteknik

Penelitian ini menyajikan permodelan matematika untuk mensimulasikan banjir rancangan pada bendun... more Penelitian ini menyajikan permodelan matematika untuk mensimulasikan banjir rancangan pada bendungan Way Apu dengan mempertimbangkan karakteristik fraktal dari DAS. Bendungan Way Apu yang terletak di Sungai Way Apu, Maluku, Indonesia di bangun sebagai bendungan multiguna seperti irigasi, pembangkit listrik tenaga air (PLTA), air baku, dan untuk pengendali banjir sebagai tujuan utama. Analisa banjir rancangan pada bendungan ini mendapatkan beberapa kendala karena besarnya curah hujan di wilayah timur Indonesia, terutama di Pulau Buru Provinsi Maluku. Desain banjir untuk Dam tipe urugan di bawah 40 m di Indonesia mengacu pada SNI-3432-1994, menggunakan kemungkinan banjir maksimum periode ulang 1000 tahun untuk perencanaan risiko besar. Makalah ini akan menganalisis desain banjir Bendungan Way Apu dengan periode ulang 1000 tahun dengan mempertimbangkan karakteristik fraktal dari DAS menggunakan hidrograf sintetik ITS-2. Hasil perhitungan menggunakan HSS ITS-2 diperoleh nilai banjir rancangan sebesar 2454,15 m 3 /dt. Perhitungan penelusuran banjir (flood routing) diperoleh penurunan debit outflow sebesar 3,65% dengan Panjang pelimpah (spillway) 60 m, dengan elevasi mercu pada elevasi +134.

Fractal characteristic of watershed is an important parameter which influences the formation of s... more Fractal characteristic of watershed is an important parameter which influences the formation of synthetic unit hydrograph. Based on a previous study, hydrology response of watershed expressed in hydrograph form could be well presented by hydrology network characteristic as a form of fractal characteristic of watershed [1]. Fractal characteristic of watershed was stated as fractal dimension which was presented in three parameters i.e. river branch ratio (RB), river length ratio (RL) and watershed river area ratio (RA). The purpose of this research was to analyze fractal characteristic and to verify its fractal dimension stability as preliminary research to prepare variables which would be used to develop synthetic unit hydrograph model in the future. Analysis was undertaken using two methods i.e. Horton's Coefficient Ratio and Box Counting Dimension. Analysis result revealed that fractal dimension of river network from 8 watersheds calculated using those two methods could give al...

Short-cut is one offlood control technique in meandering river especially in downstream reach. In... more Short-cut is one offlood control technique in meandering river especially in downstream reach. In some cases, this technique is still used although in eco-hydraulic concept, it is less effective and on the contrary, it causes bigger flood on downstream river. This research is to know the effect of short-cut on flood characteristic by using DonginRiver in Banggai Regency as model.This research is conducted with hydrology analysis to the rainfall and watershed data to set flood hydrograph as upstream boundary condition. The simulation deals with flood routing by using HEC-RAS hydrodynamic models to know the hydrograph, water surface, velocity and energy line along the river reach. To obtain the optimal parameter value, formerly, HEC-RAS must be calibrated by adjusting simulated water surface with observed water surface in a cross section.The result of simulation using annual discharge (Q1=123.54 m3/s) showed that the short-cut affect the flood characteristic and water surface profile....

Terdapat dua prosedur yang dapat digunakan untuk memperkirakan laju erosi dengan menggunakan meto... more Terdapat dua prosedur yang dapat digunakan untuk memperkirakan laju erosi dengan menggunakan metode USLE berdasarkan data historis (historical data) pada masa yang lampau. Cara pertama yakni dengan menganalisis laju erosi rata-rata bulanan untuk seluruh tahun data sekaligus. Keluaran dari cara ini adalah perkiraan laju erosi rata-rata bulanan. Cara yang kedua yakni dengan melakukan perhitungan laju erosi rata-rata bulanan untuk setiap tahun data. Perbedaan prosedur dalam memperkirakan laju erosi tersebut, memungkinkan terjadinya perbedaan angka laju erosi yang akan dinyatakan dengan angka nisbah pengangkutan sedimen (sediment delivery ratio, SDR). Penelitian ini mengkaji pengaruh kedua prosedur perkiraan laju erosi tersebut terhadap konsistensi nisbah pengangkutan sedimen. Hasil penelitian yang diterapkan pada sub-DAS Miu dan Wuno di Palu-Sulawesi Tengah menunjukkan bahwa angka nisbah pengangkutan sedimen (SDR) kedua prosedur tidak menunjukkan perbedaan yang besar, masing-masing seb...

2018 2nd Borneo International Conference on Applied Mathematics and Engineering (BICAME), 2018

ITS-2 is a synthetic unit hydrograph (SUH) model developed at the Institut Teknologi Sepuluh Nope... more ITS-2 is a synthetic unit hydrograph (SUH) model developed at the Institut Teknologi Sepuluh Nopember (ITS) in 2017. The development of this model is intended to predict the potency of flood peak based on certain rainfall inputs in the watershed system, especially in an unmeasured watershed or measured watersheds with insufficient data. The high deviation that resulted from previous similar models had low performance in the tested watershed, also the reason this SUH model was developed. The main properties of this model are the accommodation of fractal parameters of the watershed, especially in peak time equations and a very simple single curve equation derived from the two-parameter Gamma Distribution. This paper intends to introduce the ITS-2 Model to estimate flood hydrographs in various watersheds in Indonesia. By introducing this model, it is expected to be able to obtain information from various users in Indonesia regarding the performance and validity of the model, so that im...

DEStech Transactions on Engineering and Technology Research, Oct 17, 2017

The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall int... more The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall into run off for water resources development. The typical feature of this model is that the main equation represents the shape of the curve expressed by the relationship between time and discharge. In addition, the SUH model is also expressed in three parameters i.e. peak time (TP), peak discharge (QP), and base time (TB), representing the hydrograph curve equation. In general, SUH model is developed based on morphometry parameters of watershed, especially watershed area (A), main river length (L) and main river slope (S). Another approach in hydrograph modelling is based on the fractal characteristics of watershed. This study aims to develop a synthetic unit hydrograph model based on a combination of morphometry and fractal characteristics of watersheds. The three model parameters (TP, QP and TB) were predicted using multiple linear regression and compared with multiple nonlinear regression. The results of the analysis show that the two methods showed excellent performance. The estimation of SUH parameters using linear regression resulted peak time equation (TP) as function of river length (L), ratio of river length (RL) and density of drainage network (D) with determination coefficient of 99.8%, a base time equation (TB) as the function of watershed area (A) and river slope (S) with determination coefficient of 98.2%. Using multiple non linear regression, estimation of SUH parameters formulated peak time equation (TP) as function of river length (L), ratio of river length (RL) and ratio of watershed area (RA) with determination coefficient of 99.9%, a base time equation (TB) as the function of watershed area (A) and ratio of watershed area (RA) with determination coefficient of 97.9%. Peak discharge equation (QP) is stated as a function of peak time and a simple single curve equation derived from Gamma Distribution Equation.

Until today, the development of synthetic unit hydrograph model is still based on morphometry ch... more Until today, the development of synthetic unit hydrograph model is still based on morphometry characteristic of watershed or combine with other parameters. According to Sri Harto (1985), There are at least four main characteristic morphometry of watershed which highly influenced to the hydrograph and can be easily quantified namely watershed area (A), main river length (L), main river slope (S) and form factor (FB). This research aim is to analyze and verify these four factors and it's effect to the three of hydrograph parameters i.e. peak time (TP), peak flow (QP) and base time (TB). This research was carried out in eight watersheds in Central Sulawesi Province  Indonesia as the base of variable preparation to develop synthetic unit hydrograph model. Main morphometry analysis of watershed was conducted by using geographical information system (GIS) software, referring to Indonesia Topographic Map (RBI) data combined with Digital Elevation Model-Shuttle Radar Topographic Missi...

Smartek, Apr 25, 2012

A part of sediment deposition in estuary of Bengkulu River was approximately originated from Beng... more A part of sediment deposition in estuary of Bengkulu River was approximately originated from Bengkulu Watershed. The change of land use on watershed also approximately affected the rate of sheet erosion. To predict the rate of sheet erosion on Bengkulu Watershed, this research was conducted by using USLE methods and GIS. The results of this research show that the rate of sheet erosion of Bengkulu Watershed is 40.64 ton/ha/year or 2.258 mm/year. This rate is included in the 2 nd class of erosion risk (light risk) based on USDA classification (15-60 ton/ha/year). It explains that the sheet erosion on watershed give a little effect on sedimentation process in estuary. Abstrak Sebagian endapan sedimen di muara Sungai Bengkulu diperkirakan berasal dari erosi permukaan di DAS. Alih fungsi lahan (land use) di DAS juga diperkirakan telah mempengaruhi laju erosi permukaan. Untuk memprediksi laju erosi permukaan DAS Bengkulu, penelitian ini dilakukan dengan menggunakan metode USLE dan Sistem Informasi Geografis sebagai alat bantu analisis data berbasis digital. Hasil penelitian menunjukkan bahwa laju erosi permukaan DAS Bengkulu adalah 40.64 ton/ha/tahun. Angka ini setara dengan 2.258 mm/tahun dan termasuk dalam kelas bahaya erosi II (15-60 ton/ha/tahun)/ringan berdasarkan klasifikasi USDA. Hal ini berarti bahwa erosi permukaan DAS Bengkulu memberi kontribusi kecil terhadap sedimentasi di muara. Kata kunci: erosi permukaan, sistem informasi geografis, metode USLE * Staf Pengajar Jurusan Teknik Sipil Fakultas Teknik Universitas Tadulako, Palu

International Journal of Engineering and Technology

One of the important factors in water resources management is the determination of design flood a... more One of the important factors in water resources management is the determination of design flood associated with determining the size, capacity and age of the water resources structures to be built. Determination of design flood can be done in various ways, one of which is very popular to date is discharge prediction using synthetic unit hydrograph (SUH) approach. The use of unit hydrograph models has been widely applied in various parts of the world, especially in Indonesia, some of which are Snyder, Nakayasu, GAMA I and ITB-1. These methods are considered to have a good performance because it has to accommodate the characteristics of watersheds in a model parameter that greatly contributed to the process of rainfall-runoff transformation. However, in some cases it also provides a sizeable deviation, especially in Indonesia, considering that watersheds in Indonesia have different characteristics with watersheds in the United States where Snyder Unit Hydrograph developed. To overcome these problems, the unit hydrograph performance must be improved so that it can be used in various watersheds to obtain the smallest deviations. This research was conducted in 8 watersheds located in Central Sulawesi Province, Indonesia. This study aimed to improve the performance of Snyder Unit Hydrograph Model, covering Snyder, Nakayasu, SCS, GAMA I, ABG and ITB-1. The improvement of model performance was conducted by adjusting model parameters, in this case using Solver Tool on Microsoft Excel. Evaluation was done by the error indicator such as coefficient of Nash-Sutcliffe model efficiency (E). The study result showed that model parameter adjustment could decrease a deviation of SUH model parameter for peak discharge and average peak time up to 30% and could increase Nash-Sutcliffe Model Efficiency Coefficient (E) up to over 80%. The decrease of a deviation of SUH model parameter and the increase of E coefficient revealed that optimization using solver facility was effectively undertaken. However, not all deviations decreased but even increased significantly after optimization. It happened because the process of parameter optimization occurred simultaneously, and it was only based on a purpose function by maximizing Nash-Sutcliffe Model Efficiency Coefficient (E). The adjustment in this coefficient caused the increase or decrease of a parameter deviation of SUH Model depending on E value achieved on the optimization process. Overall, it could be declared that the decrease of a parameter deviation of SUH model was accompanied by the increase of Nash-Sutcliffe Model Efficiency Coefficient (E). Keywords : performance improvement, synthetic unit hydrograph, model parameters, flood prediction I. INTRODUCTION One of the important factors in water resources management and planning was flood discharge estimation functioned to determine optimum discharge size associated with dimension and a life of structures. The aim of optimum flood discharge estimation was to plan structures which did not have over a dimension (over estimated) implying on the big cost of structures or too small dimension (under estimated) causing a bigger risk of structure failures. One method that could be deployed to predict flood discharge was a hydrograph base. This method had been widely used either in overseas or in Indonesia as it was assumed to be able to imitate flood behavior from the beginning up to the end of the flood in a hydrograph format. Some of hydrograph bases particular a synthetic unit hydrograph commonly used in Indonesia, among others, were Snyder, Nakayasu, SCS, GAMA I, ABG and ITB-1. However, in some cases, these methods had obvious weaknesses because they could produce bigger deviation resulting in discharge size. Therefore, these method performances needed to be improved by adjusting their model parameters using optimization. Optimization was a procedure to maximize or minimize purpose function by changing a constraint function so that optimum value parameters could be determined. This study became very important as on 8 observed watersheds as objects of the study did not have a guidance used for references how to predict flood with the best performance. The best way produced from the optimization process was expected to be references for flood prediction, particularly in Central Sulawesi Province-Indonesia.

International Journal of River Basin Management

International Journal on Advanced Science, Engineering and Information Technology

Flood disaster in Palu River has repeatedly occurred with varying discharge magnitudes, especiall... more Flood disaster in Palu River has repeatedly occurred with varying discharge magnitudes, especially in the downstream segment near and around the estuary. The most recent flood occurred in July 2018 has inundated some areas of Palu City and resulted in a considerable impact on the socioeconomic life of the community in the city of Palu. Actually, flood prevention efforts have been undertaken by the Palu City Government and River Basin Board of Sulawesi III, one of which is by constructing levee combined with revetment along more than 5 km measured from the estuary to the upstream reach. The levee is made of soil material, while the revetment is a structure to protect the levee made of concrete. These structures were built on both sides of the river banks. However, the flood disaster always happens almost every year in this area. This paper intends to evaluate the performance of the flood control structure using Geographic Information System and HEC-RAS hydrodynamic model. The use of these tools provides the ease and efficiency of flood simulation along the river being modeled. The analysis results show that the bank capacity of Palu River is currently only effective for flood discharge below 550 m 3 /s, where the river bank capacity at the beginning of the levee and revetment design is approximately 550 m 3 /s, equivalent to the 25 years return period of discharge. The river bank capacity decreases due to sediment deposition on the river bed which were originated from the upstream watershed. This decline in cross-section capacity is estimated to be the cause of the flood disaster in parts of Palu City.

Journal Teknik Sipil Dan Infrastruktur, Jan 5, 2014

Journal Teknik Sipil Dan Infrastruktur, Oct 16, 2012

Bahan Kuliah Mahasiswa Magister Teknik Sipil Univ Tadulako

HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2020): Proceedings of the XXVII Conference on High-Energy Processes in Condensed Matter, dedicated to the 90th anniversary of the birth of RI Soloukhin

Land conversion in the Sausu Watershed, Sulawesi, Indonesia has been started massively since 1990... more Land conversion in the Sausu Watershed, Sulawesi, Indonesia has been started massively since 1990. During this period there have been changes in land cover from forest areas to more than 5,000 hectares of plantation land. The land conversion in the middle and upper watersheds is predicted to have triggered major floods which have resulted in large losses, especially in the downstream area as residential and agricultural land with an exposure area of more than 2,000 hectares. The flood in 1996 also has caused the collapse of the Upper Sausu Weir as a supplier of irrigation water for more than 7,000 hectares on the right and left sides of the river channel. This study was conducted to analyze the effect of land conversion in the watershed on increasing the flood peak using the ITS-2 Synthetic Unit Hydrograph Model, one of the flood peak prediction models developed at the Institut Teknologi Sepuluh Nopember in 2017. The research was preceded by data collection, especially rainfall data (daily and hourly), flow data and area conversion of forest land. Daily rainfall data were obtained from Sausu Rainfall Station with a range of 2000-2018, and hourly rainfall and discharge data were obtained from Nippon Koei Co Ltd. with a short range in 2002. The main research was carried out in two stages, namely, calibration to determine the optimal parameters of the ITS-2 Model and the application of the model for flood peak analysis. Rainfall as the input of the model can be defined as design rainfall with 50-year return periods, which are previously transformed to net rainfall. The losses due to evapotranspiration and infiltration were analyzed using Curve Number Method based on cover type and hydrologic condition of the watershed. The results of the analysis have indicated that land conversion in the watershed has increased the potential of peak flow to 16.5% when evaluated on these return period of flows. The peak of this flood does not seem to increase significantly compared to the great floods of the past. However, it must be understood that flooding can occur not only due to changes in land cover but can also occur due to various other factors such as changes in the characteristics of rainfall which leads to extreme rainfall with high intensity and long duration.

Journal of Ecological Engineering

High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province ... more High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province after the 2018 Palu Earthquake, one of them is in the Bangga River, Sigi Regency, Indonesia. It has caused massive impacts such as damaging agricultural and plantation areas and submerging public facilities and infrastructure and even causing fatalities. The flood carries a variety of materials, especially high concentration sediments which are thought to originate from eroded soils due to landslides induced by a 7.5 magnitude earthquake. These materials are eroded and transported by the flow at the upstream watershed due to heavy rainfall. This study intends to investigate the potential of landslides, factors that trigger floods and increased flooding after the earthquake. This research was conducted by investigating the landslides potency based on field surveys and interpretation of the latest satellite imagery, analyzing the characteristics of rainfall as a trigger for flooding, and predicting the flood potency as the primary impact of these two factors. Rainfall-flood transformation was simulated with the HEC-HMS Model, one of the freeware semi-distributed models commonly used in hydrological analysis. The model input is the configuration of river networks generated from the National DEM (DEMNAS), hourly rainfall during floods and other watershed parameters such as land cover, soil types and river slope. The similar simulation was also carried out on the condition of the watershed before the earthquake. Based on the results of the analysis, It can be inferred that flash floods in the Bangga River are mainly caused by heavy rainfall with long duration and landslide areas in the upper watershed triggered by the 2018 Palu Earthquake with an area of approximately 10.8 km 2. The greatest depth of rainfall as a trigger for flooding is 30.4 mm with a duration of 8 hours. The results of the study also showed that landslides in the upper watershed could increase the peak flood by 33.33% from 118.56 m 3 /s to 158.08 m 3 /s for conditions before and after the earthquake.

Journal of Ecological Engineering

Nowadays, the increasing intensity of extreme rainfall and changes in land use have triggered mas... more Nowadays, the increasing intensity of extreme rainfall and changes in land use have triggered massive floods in various regions of Indonesia. The changes in the characteristics of these two parameters cause an increase in the peak and duration of the flood over time. Peak and duration of flood estimation might be very useful for the national and local government because it is closely related to the effectiveness of prevention and mitigation plan in the future. A hydrograph-based model constitutes one approach to estimating them simultaneously. The objective of this research is to examine the application of ITS-2-a synthetic unit hydrograph (SUH) model which was developed at Sepuluh Nopember Institute of Technology (ITS) in 2017-for estimating the peak flood discharge as a basis for planning disaster mitigation programs. This study was carried out by testing the reliability of the ITS-2 Model using the Nash-Sutcliffe Efficiency (NSE) indicator by comparing the measured unit hydrograph and synthetic unit hydrograph derived using the model, optimizing the parameters of the model, and then analyzing the transformation of rainfall-flood discharge in the Gumbasa Watershed, one of the major watersheds in Central Sulawesi Province, Indonesia. This catchment is part of the Palu watershed, which is largely a tropical rainforest conservation area known as the Lore Lindu National Park. The input model is based on the design rainfall with a certain return period using the frequency analysis where the data was obtained from the rainfall stations in the study area. The results of the research showed that the performance of the ITS-2 model was still very good with the NSE above 80%. The difference in the peak discharge of these two unit hydrographs is relatively low, with a deviation below 10%. The optimal values of the ITS-2 Model parameter coefficients consisting of C 1 , C 2 , and C 3 were achieved at 1.29, 0.33 and 1.88, respectively. The results of the hydrograph analysis based on a 1-year to 100-year return period indicate that peak flood discharge ranges from 100 m 3 /sec to 550 m 3 /sec. From a series of analyses and tests that have been conducted in the previous and current research, it can be concluded that the ITS-2 Model can be applied to various watershed sizes, especially in Indonesia.

MATEC Web of Conferences

One popular technique used to reduce flood risk associated witha flood mitigation scheme, is norm... more One popular technique used to reduce flood risk associated witha flood mitigation scheme, is normalization of a river bank. This methodcan be effected done by adjusting the width of the river on the left andright banks, in order to increase channel capacity. The biggest obstaclemost often encountered in adjusting the river banks is insufficient landarea, both on the left and right sides. The capacity of the river channel cantherefore not be optimised, due to this limitation. This study intends toevaluate the effectiveness of river bank normalization to reduce flood riskin the Puna River, Central Sulawesi Province of Indonesia. The capacityevaluation was conducted under two conditions i.e. before and afternormalization of the river bank, using HEC-RAS Hydrodynamic Program, integrated with GIS. The level of effectiveness is measured by acomparison between the capacity of the river channel after banknormalization with the required channel capacity on 100 years returnperiod of discharge...

Jurnal Hidroteknik

Penelitian ini menyajikan permodelan matematika untuk mensimulasikan banjir rancangan pada bendun... more Penelitian ini menyajikan permodelan matematika untuk mensimulasikan banjir rancangan pada bendungan Way Apu dengan mempertimbangkan karakteristik fraktal dari DAS. Bendungan Way Apu yang terletak di Sungai Way Apu, Maluku, Indonesia di bangun sebagai bendungan multiguna seperti irigasi, pembangkit listrik tenaga air (PLTA), air baku, dan untuk pengendali banjir sebagai tujuan utama. Analisa banjir rancangan pada bendungan ini mendapatkan beberapa kendala karena besarnya curah hujan di wilayah timur Indonesia, terutama di Pulau Buru Provinsi Maluku. Desain banjir untuk Dam tipe urugan di bawah 40 m di Indonesia mengacu pada SNI-3432-1994, menggunakan kemungkinan banjir maksimum periode ulang 1000 tahun untuk perencanaan risiko besar. Makalah ini akan menganalisis desain banjir Bendungan Way Apu dengan periode ulang 1000 tahun dengan mempertimbangkan karakteristik fraktal dari DAS menggunakan hidrograf sintetik ITS-2. Hasil perhitungan menggunakan HSS ITS-2 diperoleh nilai banjir rancangan sebesar 2454,15 m 3 /dt. Perhitungan penelusuran banjir (flood routing) diperoleh penurunan debit outflow sebesar 3,65% dengan Panjang pelimpah (spillway) 60 m, dengan elevasi mercu pada elevasi +134.

Fractal characteristic of watershed is an important parameter which influences the formation of s... more Fractal characteristic of watershed is an important parameter which influences the formation of synthetic unit hydrograph. Based on a previous study, hydrology response of watershed expressed in hydrograph form could be well presented by hydrology network characteristic as a form of fractal characteristic of watershed [1]. Fractal characteristic of watershed was stated as fractal dimension which was presented in three parameters i.e. river branch ratio (RB), river length ratio (RL) and watershed river area ratio (RA). The purpose of this research was to analyze fractal characteristic and to verify its fractal dimension stability as preliminary research to prepare variables which would be used to develop synthetic unit hydrograph model in the future. Analysis was undertaken using two methods i.e. Horton's Coefficient Ratio and Box Counting Dimension. Analysis result revealed that fractal dimension of river network from 8 watersheds calculated using those two methods could give al...