Search

The Pengkol River, situated in Meteseh, Tembalang sub-district of Semarang City, underwent three significant flood occurrences from January to February 2023. An approach involving a structural flood control system, specifically a levee, was suggested as a solution to this issue. The objective of this research is to establish the arrangement and highest elevation of the levee flood control and evaluate its effectiveness in mitigating floods. To determine flood hydrographs, a hydrological analysis was carried out using the Rainfall-Runoff simulation with the SCS Curve Number method. Additionally, a hydraulic analysis was performed using Unsteady Flow simulation with HECRAS 1D/2D hydrodynamic models to define the river body, water profile, inundation, and levee design. The hydrologic analysis indicates that the flood discharge for the 50, 100, and 200-year return periods are 209.5 m³/sec, 225.1 m³/sec, and 240.6 m³/sec, respectively. Based on the hydraulic analysis, the maximum water levels resulting from these return periods' flood discharges are +35.62 m (Q50 years), +35.77 m (Q100 years), and +36.43 m (Q200 years). The Q200 years of return period was chosen for 2D modeling because it resembles documented flood occurrences. Using the HECRAS 2D Unsteady Flow model, it was found that before the levee implementation, the flooded area within the residential zone spanned 9462 m², with a peak water level of +37.3 m. With the levee application, using an existing layout with a total length of 230 m and a top levee level of +37.5 m, flooding was effectively prevented, reducing the maximum water surface elevation to +37.17 m. This demonstrates the levee's effectiveness in preventing floods. Keywords: levee, flood, HECRAS 1D 2D model, inundation. Unsteady flow.

Several cross-sections of the Jambu River, particularly around the Cikuya Bridge, have experienced bank collapse phenomena. This paper interprets the issues related to bank collapse and its impact on the flow capacity of the Jambu River, especially around the Cikuya Bridge. Morphological changes were simulated using a sediment transport model implemented in the Hydrologic Engineering Center's River Analysis System (HEC-RAS) 6.3.1, integrated with the ARS-USDA Bank Stability and Toe Erosion Model (BSTEM). The simulation results indicate that over a period of 10 years, the thalweg elevation (the lowest point of a riverbed) of the Jambu River around the Cikuya Bridge is predicted to experience deposition in 17 cross-sections and erosion in 15 cross-sections. The highest deposition occurs at the cross-section below the Cikuya Bridge, with a thalweg elevation change of 0.59 m. This warrants attention as the storage capacity of the cross-section decreases by 7% from the initial condition. Predictions indicate that bank collapse will occur in 7 cross-sections over the next 10 years. This is attributed to the steep slopes of silt and clay banks, exceeding 45 degrees, and the reduced safety factor of bank stability due to groundwater pressure influenced by river discharge fluctuations and tidal effects reaching the Jambu River. Bank collapse impacts the elevation change of the riverbed and adds load to the sediment transport model from the collapsing cross-sections to the downstream sections. Keywords: Jambu River, Cikuya Bridge, Cilacap, sediment transport, bank stability and toe erosion model

Flooding and changes in riverbed morphology often become issues near river confluences, as observed at the confluence of Citarum Hilir and Cibeet Rivers. This study aims to analyze the cross-sectional capacity and riverbed changes around the confluence of Citarum Hilir and Cibeet Rivers. This study utilizes 1D numerical modeling MIKE 11 with Hydrodynamic and Sediment Transport Modules. The hydrodynamic modeling inputs are river network and cross-sectional profiles. Hydrographs with return periods of 2, 5, 10, and 25 years are used as upstream boundaries, and a discharge curve is used as the downstream boundary of the model. The model is calibrated using water surface elevation measurements taken from September 13-16, 2021. The hydrodynamic modeling results indicate that Citarum Hilir and Cibeet Rivers cannot convey flood discharges with a 2-year return period. The sediment transport modeling results show no significant changes in the riverbed of Citarum Hilir before the confluence, but degradation of approximately 0.38 – 0.46 meters occurs after the confluence. Degradation happens in zones of maximum velocity where flow turbulence and shear stress increase, causing erosion of the Citarum Hilir riverbed. Degradation also occurs near the Cibeet River confluence due to flow acceleration at the outer bend of the river. Flooding and sediment transport are natural factors that can alter the morphology of river confluences, such as the confluence of Citarum Hilir and Cibeet Rivers. Keywords: Citarum river, Cibeet river, river confluence, hydrodinamic modeling, sedimen transport modeling

This study aims to analyze the effectiveness of sediment control structures, such as sabo and consolidation dams, and river normalization on sediment control in the Omu River after the earthquake in Sigi Regency on September 28, 2018. The analysis was conducted using the Universal Soil Loss Equation (USLE) method based on average rainfall data over 20 years. Erosion and sedimentation volumes before and after the earthquake were analyzed to understand the changes. The results showed that in 2020, the erosion volume reached 120,700.27 m³/year, and sedimentation was 17,030.81 m³/year, an increase from 2017, which recorded an erosion volume of 91,282.60 m³/year and sedimentation of 12,879.97 m³/year. Sediment transport simulation with daily discharge over 12 years indicated that in Scenario-1, sediment could be reduced by 10.81%, and in Scenario-3 by 23.18%. Meanwhile, simulation with Q100 flood discharge in Scenario-2 showed sediment reduction by 47.18%, and in Scenario-4 by 62.96%. The general conclusion of this study is that sediment control structures and river normalization are effective in reducing sediment volumes. Specifically, the construction of sediment control structures has proven to significantly reduce erosion and sedimentation. This research highlights the importance of structural improvements in mitigating post-disaster erosion impacts. The results of this study can serve as a reference for planning and implementing sediment control in disaster-prone areas. Keywords: sediment control, sabo dam, consolidation dam, river normalization, Omu river

The Western North Tarum Irrigation channel plays a crucial role in supplying water to irrigated agricultural areas. However, it encounters challenges in ensuring adequate water delivery to all channel segments. This research assesses water loss during the distribution process in the Western North Tarum Irrigation channel, focusing on the evaluation of channel capacity and the impact of suboptimal water management on water loss. The study employs the HEC-RAS model, a hydraulic system analysis tool, to evaluate the channel’s capacity and simulates its behavior under various discharge conditions. The evaluation reveals that two channel segments, B.TUB 13 and B.TUB 25, have exceeded their capacity limits, resulting in overflow. Sedimentation downstream, particularly in these segments, exacerbates the issue by altering the channel slope and impeding water flow. This research identifies poor water distribution management as a significant factor contributing to water loss in the irrigation channel. Inadequate scheduling and the absence of proper water measurement tools result in instances of overwatering or underwatering in some areas. The lack of monitoring and control in the irrigation system hampers the detection of uncontrolled flow in the channels, leading to substantial water loss and inefficient water use. This research underscores the importance of evaluating and maintaining irrigation channel capacity to prevent overflow and water loss. Furthermore, it emphasizes the significance of effective water management to achieve more efficient water distribution and irrigation. Addressing these challenges is crucial for ensuring the long-term sustainability of irrigated agriculture in the Western North Tarum Irrigation area. Keywords: HEC-RAS, Irrigation Channel, Water Distribution, Water Loss, Western North Tarum

Microplastics found in drainage channels are a significant contributor to river pollution. Among the potential contributors to this issue are industrial activities. In this investigation, we focused on assessing the occurrence of microplastics within the Surabaya Industrial Estate Rungkut (SIER) industrial area, which discharges into the Tambakoso River in East Java, Indonesia. Surface water tests were obtained from 19 particular focuses. The extraction of microplastics included filtration, wet peroxide oxidation, and density separation techniques. Recognizable proof of polymers was accomplished utilizing Fourier change infrared (FTIR) spectroscopy. Statistical analysis was conducted employing the Ward cluster test method within the IBM SPSS Statistics software. The findings revealed a gradual increase in the abundance of MPs from upstream to downstream locations, with the highest concentration observed at point 19 (548.33 particles/L). The majority of microplastics were characterized by their small size (

A study was conducted on the Katingan tidal lowland area with hydro-topography A and B. The lowland area has good irrigation capability but low drainage capability, resulting in excessive inundation. This study aims to enhance drainage capability and control water levels in rice fields. HEC-RAS is used to model the hydrodynamics of canals and rice fields. There are three scenarios for improving the water system, namely embankments (1), embankments and pipes (2), and embankments, pipes, and gates (3). In the normalized canals, inundation in the middle of the rice field is more than 35 cm and continuous inundation. This is due to the low elevation of the middle area, which results in low drainage capability. The embankment (1) prevents the tide from overflowing into the rice fields, but the rice fields are deficient in water. Embankments and pipes (2) can fulfill the water need for irrigation but not increase drainage capability. Embankments, pipes, and gates (3) can maintain irrigation capability and improve drainage capability. The water level can be maintained at 7-10 cm at land elevation +3.40 m, but land with elevation +3.50 m has a water deficiency. The third scenario is the most appropriate for controlling water levels in rice fields. Water system improvement in tidal lowlands must be considered to avoid water deficiency. Drought in tidal lowlands causes pyrite to oxidize, leading to increased soil acidity. Therefore, irrigation capability must be maintained to improve the water system on land with hydro-topography A and B.

Establishing and maintaining hydrometeorological networks in sub-watersheds is challenging. An analysis of an established network of Rain Gauge Station (RGS) is provided in this study in the form of a comprehensive statistical framework. Hydrometeorological observations are monitored by this network, which aims to gather the most pertinent information while minimizing expenditures. The study location is at Ngasinan Hulu watershed (East Java, Indonesia), with ten rain gauge stations and one automatic water level recorder (AWLR). Errors in reviewing hydrological data in a watershed can cause the resulting data to be inaccurate. Therefore, to solve the problem of incorrect data, it is necessary to rationalize rain gauge stations. The rationalization for this study uses the Stepwise method. The results of the Stepwise-Enter method produce a combination of six rain gauge stations with measured rainfall data and a combination of four rain gauge stations with CHIRPS satellite rainfall data. Therefore, this combination of rain gauge stations is rational because it meets the classical assumption test, and the area is evenly distributed according to WMO standards.

The increasing demand for drinking water due to population growth presents significant challenges for the Among Tirto Water Utility (ATWU) in Batu City, East Java, Indonesia. In 2022, ATWU faced low service coverage (36%) and high water loss (38%), exceeding the 20% threshold. Some previous research discusses the System Dynamics (SD) used to overcome the water shortage problem. In this study, the SD is used to overcome excess water. Therefore, This study aims to enhance efficiency by adding piping networks and controlling water losses. This research uses an SD approach method that includes simulations from 2017 to 2042 or for 25 years using the Powersim application. Methodologies include analyzing drinking water availability, constructing causal loop diagrams (CLD) and stock and flow diagrams (SFD), verification, validation, and designing policy scenarios. The required data are the number of customers, service coverage, actual production capacity, water loss, total community water consumption, business revenue, business expenses, and other data related to water management in ATWU. The study identifies Scenario Two as the most effective in addressing location-specific issues. If water loss control is implemented to reduce loss rates to 20%, ATWU could expand service coverage by 58.44%, increasing water availability and a projected profit of 3.6 billion rupiahs by 2042. The results of this study can improve operational efficiency and facilitate better decision-making for the Water Utility of Batu City.

The Lapindo mud phenomenon has been going on for 17 years, causing damage to the land and subsurface geological structures which raises concerns about reducing groundwater quality. This research aims to determine groundwater flow patterns based on surface contours around the Porong River which were analyzed using Surfer 13 software, and understand the relationship between groundwater and surface water through physical properties with correlation coefficients using Rstudio, as well as to identify the chemical characteristics of surface water and groundwater using the Trilinear Piper Diagram. Based on the research results, the groundwater flow pattern moves from northeast to southwest, and there is interaction between the two as indicated by the physical properties of the water. The correlation coefficient value ranges from 0.615 to 0.997, meaning that the relationship between groundwater and surface water is moderate to strong. Both groundwater and surface water have the same chemical type, namely mostly containing alkaline earth and weak acids. In addition, this research reveals the exploration of the impact of heavy metal parameters, namely Copper (Cu), from the Lapindo mud in the Porong River and residents' dug wells. In conclusion, this research shows the interaction between groundwater and surface water in the Porong River.

This study aims to determine the availability of Tilong Reservoir inflow related to climate change. Water availability can be seen from the high inflow into the reservoir, obtained using the Mock model to simulate the inflow. The modeling results using the Mock model in the historical period are then compared with the results of future projections using GCM CanESM2 data from SSP119 to SSP585 scenarios. The historical period is modeled using rainfall from 2000 to 2019, while the projection period is divided into two periods, namely the 2030s (2020-2039) and 2050s (2040-2059). The projection results show that the highest increase in rainfall will occur in the SSP245 scenario for the 2030s and 2050s. The highest increase in future rainfall occurs in June, while the highest decrease occurs in August. With the increase in rainfall, there will also be an increase in inflow into the Tilong Reservoir, especially in December, which is more than 100% for each SSP scenario. In addition, an increase in water availability can also be seen by an increase in the dependable discharge, especially at SPP245, where there was an increase in the highest dependable discharge of 64.23% in the 2030s and 76.80 in the 2050s. The increase in dependable discharge is seen to positively impact the water availability of the Tilong Reservoir. However, it is necessary to pay attention to the reservoir’s operational pattern so that the existing water can be used optimally.

This study aimed to develop strategies to improve clean water distribution services in Bumdes Sumbertlaseh Village because the distribution of clean water in the village is not optimized. The analysis used the Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis to formulate a strategy for enhancing clean water distribution services in the village. Within the SWOT analysis framework, the satisfaction level is represented by values ranging from 1 to 4, with 1 indicating low satisfaction and 4 indicating high satisfaction. The SWOT analysis concluded that clean water distribution services were in quadrant V. The appropriate strategy in this situation was market penetration and product development. In market penetration, Bumdes Sumbertlaseh Village could implement strategies such as providing additional services or enhancing the quality of existing services to retain and attract new customers. Meanwhile, in product development, Bumdes Sumbertlaseh Village could implement strategies such as constructing new pipeline networks, expanding existing networks to cover unreached areas, or improving the reliability and efficiency of existing distribution systems.

The UB Forest Buntoro area is a biodiversity conservation zone that has the potential to be developed into a tourist forest, so it is planned to build a drainage channel in each section of the road to overcome the runoff that occurs. This research aims to describe an example of the application of BIM in construction planning for drainage channels. In this study, drainage channel planning was done using AutoCAD Civil 3D and Storm and Sanitary Analysis (SSA) software. The AutoCAD Civil 3D application is used to create a road route for which drainage channels are planned, and the SSA is used to analyze the hydrology and hydraulics of the drainage channel. Based on Building Information Modeling findings, the optimal drainage channel design yielded channel dimensions of 0.4 m × 0.4 m. The main channels (RC (Right Channel) and LC (Left Channel)) are planned to use gabion material, while the culverts are planned to use u-ditch material and a construction planning cost of 1.571.818.500,00 IDR. This study intends to give an example of how Building Information Modeling (BIM) is applied in Indonesia, particularly in the area of water resources. It does this by utilizing AutoCAD Civil 3D and SSA programs to design drainage channels.

Currently, Batu City is experiencing rapid development both in terms of population and the amount of land building. Where development is uncontrolled and not balanced by reasonable conservation efforts, it will cause water resource problems such as flooding. So, it is necessary to understand flow patterns better as an actual effort in effective water management and flood hazard mitigation. This study aims to obtain a map of flood-prone areas in the Brantas sub-watershed upstream of Batu City. The primary methodology adopted in this research entails the examination of surface runoff through the utilization of the ArcSWAT program, followed by the analysis of pertinent parameters, including rainfall, land use, soil type, land slope, river density, and surface runoff. Then, scoring and weighting are done before overlaying each parameter to get a flood vulnerability map at the research location. The results of this study indicate that the mapping of flood-prone areas at the most significant research location is at a high level of flood vulnerability of 78.31 km2 or 52.22% of the total area of the watershed.

This research confronts the pressing challenge of escalating clean water demand in Bandung, a dynamically expanding metropolitan city in Indonesia's West Java Province. Drawing on secondary data from the Central Bureau of Statistics and other relevant literature, the study leverages Microsoft Excel to perform a dual analysis: forecasting population growth and calculating future water demand through 2032. A pivotal outcome reveals that the existing water supply infrastructure in Bandung will be woefully insufficient to meet the exponentially growing clean water requirements. Uniquely, this study employs multiple forecasting methodologies, adding depth and reliability to the projections. It there by offers new, essential insights into the quantifiable volume of water that will be needed to sustain future urban development. The research argues that current supply-focused water management strategies are inherently flawed and calls for an immediate paradigm shift toward demand-side management to mitigate the impending water crisis. Specific recommendations include the incorporation of alternative water sources such as rainwater harvesting and groundwater recharge. Moreover, the study emphasizes the need for rapid governmental action, including policy revision and public education campaigns, to ensure water sustainability. This research stands as a critical resource for policymakers, urban planners, and water management experts aiming to bridge the looming water supply-demand gap in Bandung.

ABSTRACT Implementation of zero delta Q located at Polytechnic of Public Works specifically at Student Apartment is conducted by infiltrating runoff into the ground. The objectives of this study are to analyze runoff volume based on rainfall-runoff analysis and the quantity of water that can be absorbed based on soil permeability. The methods used were 1-dimensional (1-D) and 2-dimensional (2-D) of geoelectric tests. Soil permeability tests was added to and calculate the capacity of the infiltration wells. The research analysis was done using primary data including the measurement result of topography, geo-electric, soil permeability, and water quality , as well as secondary data of rainfall data for 10 years from 2011-2020, DEMNAS, geological map, groundwater basin, aquifer productivity, and a tower development master plan. The results of 1-D and 2-D geoelectrical analysis showed that the soil conditions in the study area were saturated and it was difficult to absorb water into the soil, and the permeability test showed a low value of soil permeability. Based on the calculation of infiltration well capacity, 554 infiltration wells are required to absorb the runoff, but it is difficult to carry out due to the limitation of available land area. Therefore, zero delta Q must be applied through other efforts, for instance by implementing reuse mechanism of runoff. Based on the analysis, the reuse of runoff can fulfill the water needs of 288 people. However, the reuse of runoff at the research location requires prior processing so it is suitable for water quality standards. Keywords: zero delta Q, geoelectric test, infiltration, runoff, permeability ABSTRAK Salah satu upaya penerapan zero delta Q di Kampus Politeknik PU tepatnya rusun mahasiswa dilakukan dengan peresapan air limpasan hujan ke dalam tanah. Tujuan penelitian ini yaitu menganalisis volume limpasan berdasarkan analisis curah hujan-limpasan dan kuantitas air yang dapat diresapkan berdasarkan permeabilitas tanah. Metode yang digunakan adalah uji geolistrik 1 dimensi (1-D) dan 2 dimensi (2-D). Uji permeabilitas tanah diterapkan untuk menghitung kapasitas sumur resapan. Analisis penelitian dilakukan dengan data primer berupa hasil pengukuran topografi, geolistrik, permeabilitas tanah, dan kualitas air, serta data sekunder berupa data hujan yang diperoleh dari stasiun hujan BMKG Semarang, stasiun hujan Bandara Ahmad Yani, dan stasiun hujan Maritim Tanjung Mas selama 10 tahun dari tahun 2011-2020, data DEMNAS, peta geologi, data cekungan air tanah, data produktivitas akuifer, dan master plan pembangunan rusun. Hasil analisis dengan geolistrik 1-D dan 2-D menunjukkan kondisi tanah di lokasi penelitian jenuh air dan sulit untuk meresapkan air ke dalam tanah, di samping itu pengujian dengan permeabilitas menunjukkan nilai permeabilitas tanah rendah. Berdasarkan perhitungan kapasitas sumur resapan, diperlukan sebanyak 554 buah sumur resapan untuk meresapkan limpasan yang terjadi, kondisi ini sulit dilakukan karena keterbatasan lahan. Oleh karena itu penerapan zero delta Q perlu dilakukan melalui upaya lain misalnya dengan penggunaan kembali limpasan air hujan. Berdasarkan analisis, penggunaan kembali limpasan air hujan dapat memenuhi kebutuhan air untuk 288 orang, namun penggunaan kembali limpasan air hujan di lokasi penelitian memerlukan pengolahan terlebih dahulu agar memiliki kualitas air yang sesuai baku mutu air kelas 4 PP nomor 22 tahun 2021. Kata Kunci: zero delta Q, uji geolistrik, resapan, limpasan, permeabilitas

ABSTRACT Studies related to baseflow modeling are still rarely carried out compared to flood modeling. The commonly used rainfall-runoff models oversimplify the baseflow process, which leads to poor low-flow simulations. Baseflow plays an important role in regulating the seasonal distribution of river flow, maintaining aquatic habitats, and transporting chemical nutrients in the river system. If the baseflow decreases in the Citarum Watershed, there will be consequential impacts on the Java-Bali electricity supply, rice field irrigation water, raw water, and industrial water in West Java and DKI Jakarta. This study evaluates six lumped-rainfall-runoff models that are popularly used in the Ministry of Public Works and Housing of Indonesia, namely Mock, NRECA, HBV96, NAM, Sacramento, and Empirical to simulate baseflow on the Nanjung Subwatershed and Cisokan Subwatershed. The baseflow simulations from each model are compared with the observational baseflow. The observational baseflow is obtained using the Recursive Digital Filter Lyne and Holick one filter methods. To quantify model comparison, a multi-criteria matrix is used consisting of the model convenience, baseflow parameters, and model performance. This study shows that the Mock Model gives the best results with a "Satisfactory" score for simulating baseflow in NSE and RMSE values, the Q50-Q80 differences, and the difference in flow heights compared to the other five models. In addition, the Mock Model is also relatively easy, accessible, and familiar to use. Keywords: Baseflow, Rainfall-Runoff, Lumped, Citarum, Recursive Digital Filter ABSTRAK Kajian terkait pemodelan aliran dasar masih jarang dilakukan dibandingkan pemodelan banjir. Model hujan-aliran yang umumnya digunakan mengasumsikan perhitungan aliran dasar secara sederhana sehingga menghasilkan simulasi aliran rendah yang buruk. Padahal penentuan aliran dasar sangat diperlukan mengingat pentingnya fungsi aliran dasar dalam mengatur distribusi musiman aliran sungai, mempertahankan habitat air, dan mengangkut nutrisi-bahan kimia dalam sistem sungai. Apabila terjadi penurunan aliran dasar di Daerah Aliran Sungai (DAS) Citarum maka dampaknya akan signifikan pada pasokan listrik Jawa-Bali, air irigasi sawah, air baku, dan air industri di Jawa Barat dan DKI Jakarta. Penelitian ini mengevaluasi enam model hujan-aliran lumped yang populer digunakan di Kementerian PUPR, yaitu Mock, NRECA, HBV96, NAM, Sacramento, dan Empiris untuk menentukan besarnya aliran dasar pada Sub-DAS Nanjung dan Sub-DAS Cisokan. Hasil pemodelan kemudian dibandingkan dengan hasil pemisahan aliran dasar dari debit observasi yang diperoleh melalui Metode Recursive Digital Filter Lyne dan Holick satu filter. Untuk memudahkan perbandingan model, digunakan matriks multi-kriteria dengan parameter pembanding kemudahan pemodelan, ada tidaknya parameter aliran dasar, dan kinerja model. Penelitian menunjukkan Model Mock memberikan hasil paling baik dengan skor “Memuaskan” untuk mensimulasikan aliran dasar di lokasi kajian berdasarkan nilai NSE dan RMSE, selisih Q50-Q80, dan selisih tinggi aliran dibandingkan kelima model lain. Selain itu, Model Mock juga relatif mudah, aksesibel, dan familiar untuk menentukan aliran dasar di lokasi kajian. Kata Kunci: Aliran dasar, Hujan-Aliran, Lumped, Citarum, Recursive Digital Filter

ABSTRACT Dadahup lowland irrigation area is one of the areas developed as a food estate. Land cover change to shrubs is caused by channels with buildings that are not functioning optimally, so it is often hit by floods and droughts. One of the efforts to improve the function of channels and buildings is to control the minimum water level of 60 cm in the dry season and the maximum water level of 10 cm in the rainy season. This study aims to determine the optimal operations and maintenance through adjusting the elevation of the gate opening to achieve the quantity and quality for the development of water management systems in lowland irrigation. The research method was carried out with hydraulic simulation based on the tides of the Barito River Mouth, discharge, rainfall, and pH obtained from telemetry monitoring system with openings of all sluice gates in primary channels and secondary channels. The results showed that operation and maintenance optimization can be done by setting primary and secondary sluice gates that are opened at a water level elevation above + 0.5 m in the dry season as supply and water level elevation + 1.1 m in the rainy season as drainage. Primary and secondary sluice gates are closed at water levels below + 0.5 m to maintain water levels and water quality. Keywords optimization, lowland, Dadahup Lowland Irrigation Area , HEC-RAS, hydraulic ABSTRAK Daerah irigasi rawa Dadahup merupakan salah satu daerah yang dikembangkan sebagai lumbung pangan. Perubahan tutupan lahan menjadi semak belukar disebabkan oleh saluran dengan bangunan yang tidak berfungsi secara optimal sehingga sering dilanda banjir dan kekeringan. Salah satu upaya untuk meningkatkan fungsi saluran dan bangunan adalah dengan mengendalikan tinggi muka air minimum 60 cm pada musim kemarau dan tinggi muka air maksimum 10 cm pada musim hujan. Penelitian ini bertujuan untuk mengetahui pola operasi dan pemeliharaan yang optimum melalui pengaturan pintu dalam mencapai kuantitas dan kualitas air yang sesuai untuk pengembangan sistem tata air di lahan irigasi rawa. Metode penelitian dilakukan dengan simulasi hidraulika berdasarkan pasang surut muara Sungai Barito, debit, curah hujan, dan pH yang diperoleh dari sistem monitoring telemetri dengan bukaan setiap pintu air pada saluran primer serta saluran sekunder. Hasil penelitian menunjukkan bahwa optimasi operasi dan pemeliharaan dapat dilakukan dengan pengaturan pintu air primer dan sekunder yang dibuka pada elevasi muka air di atas + 0,5 m pada musim kemarau sebagai supply dan elevasi muka air + 1,1 m pada musim penghujan sebagai drainase. Pintu air primer dan sekunder ditutup pada elevasi muka air di bawah + 0,5 m untuk menjaga tinggi muka air dan kualitas air. Kata Kunci: optimasi, rawa, Daerah Irigasi Rawa Dadahup, HEC-RAS, hidrolika

ABSTRACT The Semantok Dam, located in Rejoso District, Nganjuk Regency, has a total length of 3,005 m and a height of 26 m with a zonal type of fill. The dam body uses 5 types of natural materials as its constituent parts, namely lempung as the core, sand as a fine filter, gravel as a coarse filter, random soil as the dominant material, riprap and rocktoe materials as surface layers. The core material of the dam is lempung which meets the requirements to overcome seepage problems in the dam body. However, the volume of lempung material required is very large with high compaction. Therefore, it is necessary to plan alternative uses of replacement materials in the form of impermeable geosynthetics to reduce the thickness of the dam core. In planning, stability and seepage requirements must still be met. To carry out an analysis of the combined use of geomembran HDPE 2 mm in various variations in the thickness of the core zone, the Geo-Studio auxiliary program was used, where the Seep/W program was used to determine seepage and phreatic lines in the dam body, while the Lereng/W program was used to check the stability of the dam body. From several dam core thicknesses analyzed, the use of 2 mm HDPE geomembran material combined with 2/3 of the thickness of the existing core zone provides results that meet the requirements for seepage and dam stability. To overcome seepage under the dam body, secant piles are installed under the dam. The effect of earthquake loads was also analyzed where the dam remained safe for OBE earthquake loads of 100 years and 145 years; at an MDE of 10,000, the dam will experience minimum damage which still meets the requirements of 50% of the safety height with a deformation or diversion value of 15.36 cm. Keywords: Semantok Dam, weir core, geomembran, stability, seepage ABSTRAK Bendungan Semantok yang terletak di Kecamatan Rejoso Kabupaten Nganjuk memiliki panjang total mercu bendungan 3.005 m dan tinggi tubuh bendung 26 m dengan jenis urukan tipe zonal. Tubuh bendungan menggunakan 5 jenis material alam sebagai penyusunnya yaitu lempung sebagai inti, pasir sebagai filter halus, kerikil sebagai filter kasar, random tanah sebagai material dominan, serta material riprap dan rocktoe sebagai lapisan permukaan. Material inti bendungan adalah tanah lempung yang memenuhi syarat untuk mengatasi masalah rembesan di tubuh bendungan. Hanya saja, volume material lempung yang dibutuhkan sangat banyak dengan pemadatan yang tinggi. Oleh sebab itu, perlu direncanakan alternatif pemakaian material pengganti berupa geosintetik yang kedap untuk mengurangi ketebalan inti bendungan. Dalam perencanaannya, persyaratan stabilitas dan rembesan harus tetap dipenuhi. Untuk melakukan analisis terhadap kombinasi penggunaan geomembran HDPE 2 mm pada berbagai variasi ketebalan zona inti, digunakan program bantu Geo-Studio dimana program Seep/W untuk mengetahui rembesan dan garis freatik dalam tubuh bendungan, sedang program Lereng/W untuk cek stabilitas tubuh bendungannya. Dari beberapa ketebalan inti bendungan yang dianalisis, penggunaan material geomembran HDPE 2 mm yang dikombinasi dengan 2/3 ketebalan zona inti eksisting memberikan hasil yang memenuhi syarat rembesan dan stabilitas bendungan. Untuk mengatasi rembesan di bawah tubuh bendungan, secant pile dipasang di bawah bendungan. Pengaruh beban gempa juga dianalisis dimana bendungan tetap aman untuk beban gempa OBE 100 tahun dan 145 tahun; pada MDE 10.000, bendungan akan mengalami kerusakan minimum yang masih memenuhi syarat 50% tinggi jagaan dengan nilai deformasi atau alihan sebesar 15,36 cm. Kata Kunci: Bendungan Semantok, inti bendung, geomembran, stabilitas, rembesan

ABSTRACT Bogor City, renowned for its high rainfall value, has experienced rapid economic growth, leading to a substantial surge in population. This, in turn, has prompted extensive development, disrupting land use in the urban area. Consequently, effective area planning incorporating an adequate drainage system is imperative to mitigate flooding. The Cileuwibangke River, located south of Bogor City, traverses a residential area earmarked for conversion into commercial and industrial zones. Therefore, evaluating the floodwater level of the Cileuwibangke River is crucial, both in its existing state and post-construction. This study utilized daily data from the Gadog Rainfall Station and hourly data from the GPM satellite spanning from 2001 to 2020 for rainfall analysis. It revealed that several rain events exceeded the 2, 5, and 10-year return periods. Rainfall-runoff analysis showed that changes in land use resulted in a 35-36% increase in peak flood discharge and a 22-28% increase in runoff volume compared to the existing condition. The findings indicated that the normalization of the river section on the residential area side did not significantly lower the floodwater level, attributed to three broad-dimension culverts. Moreover, strengthening the river's bottom and banks is essential due to the observed hydraulic jump indication. Upstream riverbed protection can be achieved with a 35 m stretch of rock material. Keywords: Bogor City, Cileuwibangke River, HEC-HMS, HEC-RAS, and Urban Flood ABSTRAK Kota Bogor, dikenal dengan curah hujannya yang tinggi, mengalami pertumbuhan ekonomi yang tinggi sehingga menyebabkan peningkatan jumlah penduduk yang cukup pesat. Hal ini memicu pembangunan besar-besaran yang mengubah fungsi lahan di kawasan perkotaan. Oleh karena itu, perencanaan kawasan dengan sistem drainase yang memadai diperlukan untuk mencegah terjadinya banjir. Sungai Cileuwibangke, yang terletak di selatan Kota Bogor, mengalir melalui kawasan pemukiman yang akan dikembangkan menjadi kawasan komersial dan industri. Sehingga, perlu dilakukan evaluasi tinggi muka air banjir Sungai Cileuwibangke baik pada kondisi eksisting maupun setelah konstruksi. Studi ini menggunakan data harian Pos Hujan Gadog dan data jam-jaman satelit GPM dari tahun 2001 hingga 2020 untuk melakukan analisis curah hujan. Ditemukan bahwa beberapa kejadian hujan memiliki nilai lebih besar dari hujan rencana periode ulang 2, 5, dan 10 tahun. Berdasarkan analisis curah hujan-limpasan yang dilakukan, diketahui bahwa alih fungsi lahan mengakibatkan peningkatan debit banjir puncak dan volume limpasan masing-masing sebesar 35-36% dan 22-28% dibandingkan dengan kondisi eksisting. Hasil penelitian menunjukkan bahwa normalisasi ruas sungai di sisi pemukiman tidak menurunkan debit banjir secara signifikan, dikarenakan adanya tiga gorong-gorong berdimensi lebar pada kawasan tersebut. Selain itu, perlu dilakukan perkuatan dasar sungai dan bantaran sungai dikarenakan adanya indikasi loncatan hidraulik. Perlindungan dasar sungai dapat dilakukan di hulu dengan menggunakan material batuan sepanjang 35 m. Keywords: Banjir Perkotaan, HEC-HMS, HEC-RAS, Kota Bogor, dan Sungai Cileuwibangke

ABSTRACT On Thursday, July 14, 2022, a flash flood occurred in Pati Regency, Central Java, caused by heavy rainfall with an intensity of up to 147.5 mm/day on the slopes of Mount Muria. resulting several rivers in Pati Regency overflowed, causing damage to embankments and triggering a flash flood that devastated residential areas and agricultural land. In this study, a simulation was conducted to estimate the extent of the affected area by flash floods in the Sat River, Pati Regency, in the future. The study utilized HEC-RAS version 6.2, which is capable of accurately simulating non-Newtonian fluid behavior, thus enabling precise simulation of flash floods. The simulation results revealed that the flash flood in the Sat River, Pati Regency, had an impacted area of 655 hectares with an average water depth of 3.25 meters for a 2-year return period. For a 25-year return period, the impacted area increased to 1,017 hectares with an average water depth of 3.04 meters, while for a 50-year return period, the impacted area reached 1,091 hectares with an average water depth of 3.01 meters. This research provides a better understanding of the impact of flash floods in the Sat River, Pati Regency, and can serve as a reference for future disaster mitigation efforts. By knowing the extent of the affected area and the average water depth, more effective preventive and management measures can be implemented to mitigate the significant losses caused by flash floods. Keywords: flash flood, flood mitigation, flood simulation, HEC-RAS, hydraulic analysis, Pati Regency ABSTRAK Pada Kamis, 14 Juli 2022, banjir bandang terjadi di Kabupaten Pati, Provinsi Jawa Tengah yang disebabkan oleh curah hujan dengan intensitas mencapai 147,5 mm/hari di lereng Gunung Muria. Akibatnya, sejumlah sungai di Kabupaten Pati meluap, menyebabkan kerusakan pada tanggul dan memicu banjir bandang yang merusak permukiman penduduk serta lahan persawahan. Dalam penelitian ini, dilakukan simulasi dengan tujuan untuk memperkirakan luas area yang terdampak banjir bandang di Sungai Sat, Kabupaten Pati, di masa depan. Studi ini menggunakan perangkat lunak HEC-RAS versi 6.2 yang memiliki kemampuan untuk melakukan simulasi fluida dengan sifat non-Newtonian, sehingga simulasi banjir bandang dapat dilakukan secara akurat. Hasil dari simulasi menunjukkan bahwa banjir bandang di Sungai Sat, Kabupaten Pati, memiliki luas terdampak sebesar 655 hektar dengan kedalaman air rata-rata mencapai 3,25 meter untuk periode ulang 2 tahunan. Pada periode ulang 25 tahunan, luas dampak meningkat menjadi 1.017 hektar dengan kedalaman air rata-rata sebesar 3,04 meter, sedangkan untuk periode ulang 50 tahunan, luas dampak mencapai 1.091 hektar dengan kedalaman air rata-rata sebesar 3,01 meter. Penelitian ini memberikan pemahaman yang lebih baik mengenai dampak banjir bandang di Sungai Sat, Kabupaten Pati, dan dapat digunakan sebagai acuan dalam upaya mitigasi bencana di masa depan. Dengan mengetahui luas area yang terdampak dan kedalaman air rata-ratanya, langkah-langkah pencegahan dan penanganan yang lebih baik dapat diambil untuk menghindari kerugian besar yang ditimbulkan oleh banjir bandang. Kata Kunci: Analisis Hidrolika, Banjir Bandang , HEC-RAS, Kabupaten Pati, Mitigasi Banjir, Simulasi Banjir

ABSTRACT Nusa Dua Beach, Bali, is morphologically dynamic because it is constantly changing due to erosion and accretion. In 2003, the efforts were made to develop groins, where this one of the solutions to overcome erosion. Analysis of shoreline changes needs to be carried out to see the effectiveness of groin development by looking at the shoreline before and after construction using Landsat imagery data for 26 years. This research method utilizes the Modified Normalized Difference Water Index (MNDWI) algorithm to separate water from land features, classify images into four classes: sand, water, foam, and land features using the Coastsat toolkit and calculate wave energy flux. Before the construction, The GA1-GA2 groins experienced successive erosion in 1996-2002. After construction of the coastal groins, it still shows a decline in the coastline both during the west monsoon, which is 63.68 m and the east monsoon which is 36.21 m. In the east monsoon, the wave energy flux is most significant, with a maximum value of 4.9 x 10³ N/s, and in the west monsoon 3.4 x 10³ N/s. The effect of the significant wave energy flux that occurs in the east monsoon causes more longshore sediment transport, and the coast experiences a maximum shoreline advance in the east monsoon of 65.24 m compared of the west monsoon shoreline, which is 58.28 m. The toolkit can identify with better accuracy by validating estimation and observation data with an RMSE value of 4.79 m, a bias of 2.62 m, and an R2 of 0.97. Keywords: Shoreline, Erosion, Landsat, Wave Energy Flux ABSTRAK Pantai Nusa Dua, Bali dapat dikatakan secara morfologi dinamis dikarenakan selalu mengalami perubahan akibat erosi dan akresi. Tahun 2003 telah dilakukan upaya pembangunan groin yang merupakan salah satu solusi untuk menanggulangi terjadinya erosi. Analisis perubahan garis pantai perlu dilakukan untuk melihat efektivitas dari pembangunan groin dengan melihat garis pantai sebelum dan sesudah pembangunan dengan memanfaatkan data citra Landsat selama 26 tahun. Metode penelitian ini memanfaatkan algoritma Modified Normalized Difference Water Index (MNDWI) untuk memisahkan air dari fitur daratan, mengklasifikasi citra menjadi empat kelas: pasir, air, buih dan fitur lahan dengan menggunakan toolkit Coastsat serta menghitung fluks energi gelombang. Sebelum pembangunan groin GA1-GA2, pantai mengalami erosi pada tahun 1996-2002. Setelah pembangunan groin pantai masih menunjukkan terjadi kemunduran garis pantai pada saat musim barat 63,68 m maupun musim timur 36,21 m. Pada musim timur fluks energi gelombang terbesar dengan nilai maksimum 4,9 x 10³ N/s dan pada musim barat fluks energi maksimum yaitu sebesar 3,4 x 10³ N/s Efek dari besarnya fluks energi gelombang yang terjadi di musim timur menyebabkan angkutan sedimen sejajar pantai lebih besar dan pantai mengalami kemajuan garis pantai maksimum di musim timur 65,24 m dibandingkan dengan musim barat 58,28 m. Toolkit coastsat mampu mengindentifikasi garis pantai lebih efisien dengan ketelitian lebih baik dengan validasi data estimasi dan observasi bernilai RMSE 4,79 m, bias 2,62 m dan R2 0,97. Kata Kunci: Garis Pantai, Erosi, Landsat, Fluks Energi Gelombang

ABSTRACT The landslide occurred in the Lahat-Pagaralam road section on February 2, 2019. The landslide caused the road to be cut off for several days. The disconnection of roads triggered disruption of economic activity. The landslide might be caused by a puddle of rainwater seeping into the road. Several cases of landslide triggered by ponding water also occurred on the Kuningan-Tasikmalaya road in Cikijing Tasikmalaya, and on the Gempol-Pandaan toll road in East Java. The purpose of this study, therefore, was to determine the safety criteria based on the results of safety factors, the amount of seepage, and the pattern of collapse of the road, thus the incidents can be anticipated and are expected not to occur in other locations. The research method begins with field survey, depicting the geometry of the road, and collecting geotechnical data for landslide locations. Slope stability modeling due to water infiltration was processed using the SLOPE-W program. The results of road slope stability modeling at the landslide location show that when there is a 1m inundation, the slope stability value of factor of safety (FS) is 0.916 (a condition prone to landslides). The direction of flow comes from right to left, the right is a small slope and the left slope is a river bank. The difference in water level on the right and left of the road causes water to seep into the soil layer and cause the groundwater level to rise. The occurrence of water flow along the soil pile, causing water to fill the gaps between soil. The value of the slope stability number decreases due to water infiltration into the soil, resulting in landslides. SF value decreases from 0.916 to 0.887 when the inundation height increases from 1 m to 5 m. We concluded that the presence of water ponding around the road strongly suspected to be the cause of landslides. It is necessary to prevent ponding with a drainage system, so that it will not affect to the stability of the road. Keywords: landslide, slope stability, water infiltration, water ponding, drainage. ABSTRAK Telah terjadi longsor pada ruas jalan Lahat-Pagaralam pada 2 Februari 2019. Longsoran menyebabkan jalan terputus selama beberapa hari. Terputusnya ruas jalan menyebabkan gangguan aktivitas ekonomi. Longsor diduga disebabkan adanya genangan air hujan yang meresap ke badan jalan. Beberapa kasus longsor yang dipicu oleh genangan air juga terjadi pada ruas jalan Kuningan-Tasikmalaya di Cikijing Tasikmalaya, dan pada ruas tol Gempol-Pandaan Jawa Timur. Tujuan dari penelitian ini adalah untuk mengetahui kriteria keamanan lereng berdasarkan hasil analisis yang berupa angka faktor keamanan dan jumlah debit rembesan serta pola runtuh/longsor pada badan jalan, sehingga kejadian seperti ini bisa diantisipasi dan diharapkan tidak terjadi di lokasi lain. Metode penelitian diawali dengan survei lapangan, penggambaran geometri badan jalan, dan pengumpulan data geotek tanah lokasi longsor. Pemodelan stabilitas lereng akibat infiltasi air dilakukan dengan progran SLOPE-W. Hasil pemodelan stabilitas lereng jalan di lokasi longsor menunjukkan bahwa saat terjadi genangan 1m maka nilai stabilitas lereng (factor of safety FS) adalah 0,916 (kondisi rawan terjadi longsor). Arah aliran datang dari kanan ke kiri badan jalan, lereng kanan berupa alur kecil dan lereng kiri merupakan tebing sungai. Perbedaan tinggi muka air di kanan dan kiri menyebabkan air merembes masuk ke dalam lapisan tanah dan menjadikan muka air tanah naik. Terjadinya aliran air sepanjang timbunan tanah, mengakibatkan air mengisi celah antar butir. Nilai angka stablitas lereng turun akibat infiltrasi air ke dalam tanah, sehingga terjadi longsor. Nilai SF turun dari 0,916 menjadi 0,877 ketika tinggi genangan naik dari 1 m menjadi 5 m. Kajian ini menyimpulkan bahwa keberadaan genangan air di sekitar jalan diduga kuat menjadi penyebab terjadinya longsoran. Oleh karena itu, perlu dicegah terjadinya genangan dengan sistem drainase sehingga tidak mempengaruhi stabilitas lereng jalan. Kata kunci: longsor, stabilitas lereng, infiltasi air, genangan air, drainase

ABSTRACT Sedimentation is a problem that can cause siltation and changes in river morphology due to reduced river capacity and increased runoff. The Tondano River is one of the major rivers that cross the City of Manado, which has a significant contribution in terms of the impact of flooding and, in its current conditions, has experienced considerable siltation so that the capacity of the river is unable to carry discharge. This study aims to analyze the changes in the elevation of the Tondano River bed that occurred within 6 years from 2016 to 2022 due to sedimentation. Sedimentation modelling is done using the HEC-RAS 6.1 application because, it has new features and improvements over the previous version, especially for, sediment transport analysis using the Meyer Peter Muller empirical equation. The bathymetric data used is the 2016 measurement, and a sediment model simulation is carried out for a 6-year daily discharge period. Then verification is carried out with the 2022 bathymetry data and current field conditions. The results show that the Tondano River on the Kairagi section, along 7.20 km from the estuary, experienced a significant change in riverbed elevation due to sedimentation. There was an average aggradation or sedimentation thickness of 0.891 m for 6 years and an estimated 0.130 to 0.140 m per year, so under these conditions, the cross-section of the Tondano River experienced siltation and reduced the capacity of the river to carry flood discharge. The simulation results showed that changes in river bed elevation also cause an increase in water level as high as 1 to. 2 m. From the simulation results of changes in the bottom of the Tondano River section of Kairagi, a total sedimentation amount of 83,087.49 m3 for 6 years was obtained. Keywords: sedimentation, river bed elevation, water surface elevation, aggradation, deposition ABSTRAK Sedimentasi merupakan permasalahan yang dapat menyebabkan terjadinya pendangkalan dan perubahan morfologi sungai karena berkurangnya kapasitas sungai sehingga terjadi peningkatan aliran permukaan. Sungai Tondano adalah salah satu sungai besar yang melintas di Kota Manado yang menjadi salah satu sungai yang memiliki kontribusi besar dalam hal dampak banjir dan pada kondisi saat ini telah mengalami pendangkalan yang signifikan sehingga kapasitas sungai tidak mampu dalam mengalirkan debit. Tujuan penelitian ini yaitu untuk menganalisis perubahan elevasi dasar Sungai Tondano yang terjadi dalam kurun waktu 6 tahun dari tahun 2016 hingga 2022 akibat sedimentasi. Pemodelan sedimentasi dilakukan menggunakan aplikasi HEC-RAS 6.1 karena pada versi ini terdapat beberapa fitur baru dan perbaikan dari versi sebelumnya, yaitu persamaan angkutan sedimen menggunakan persamaan empiris Meyer Peter Muller. Data batimetri yang digunakan adalah pengukuran tahun 2016 dan dilakukan simulasi model sedimen selama periode debit harian 6 tahun kemudian dilakukan verifikasi dengan data batimetri tahun 2022 serta kondisi lapangan saat ini. Hasilnya dapat disimpulkan bahwa Sungai Tondano pada ruas Kairagi sepanjang 7,20 km dari muara mengalami perubahan elevasi dasar sungai yang cukup signifikan akibat sedimentasi. Terjadi agradasi atau tebal sedimentasi rata-rata sebesar 0,891 m selama 6 tahun dan diperkirakan sebesar 0,130 s.d 0,140 m per tahun, sehingga dengan kondisi tersebut penampang Sungai Tondano mengalami pendangkalan dan menyebabkan berkurangnya kapasitas sungai dalam mengalirkan debit banjir. Hasil simulasi perubahan elevasi dasar sungai tersebut juga menunjukkan terjadinya kenaikan elevasi muka air setinggi 1 s.d. 2 m. Dari hasil simulasi perubahan dasar Sungai Tondano ruas Kairagi diperoleh total besaran sedimentasi sebesar 83.087,49 m3 selama 6 tahun. Kata Kunci: sedimentasi, elevasi dasar sungai, elevasi muka air, agradasi, pengendapan

ABSTRACT The Maen Village, Minahasa Utara Regency, Province of North Sulawesi, is located adjacent to the sea and on the confluence of three rivers namely Maen Besar River, Maen Kecil (Atas) River, and Maen Kecil (Samping) River. Hence, the village area is prone to flooding, especially when heavy rainfall and high tide water occur. Therefore, this research was conducted to study levee design as the flood solution for such a village. In this work, the flood simulation was conducted using a hydrodynamic model NUFSAW2D to predict the inundation pattern for the existing condition. It was shown that the existing levee constructed for the Maen Besar River could anticipate the 2-year return period flood. However, the capacity of the Maen Kecil River was insufficient for the 2-year flood, and consequently, it caused flooding in the Maen Village. For the 25-year return period flood, all the rivers had insufficient capacity. To deal with this problem, levee design was proposed, for which the crest level of the existing levee of the Main Besar River must be increased and the new levee toward its upstream part must be constructed. Meanwhile, along the Maen Kecil River, new levee must be constructed. The simulation results using NUFSAW2D showed that with such a levee system, the Maen Village became safe from the 25-year flood. Additionally, it was required to add two retention ponds to collect the overland flow water from the Main Village, and later to flow it back to the Maen Besar and Maen Kecil Rivers. The result of this study is expected to be useful for the related stakeholders to solve the flood problem for the Main Village. Keywords: flood, Maen Village, NUFSAW2D, levee ABSTRAK Desa Maen, Kabupaten Minahasa Utara, Provinsi Sulawesi Utara, terletak berbatasan dengan laut serta berada di pertemuan antara tiga sungai yaitu Sungai Maen Besar, Sungai Maen Kecil (Atas) dan Sungai Maen Kecil (Samping). Hal ini menyebabkan kawasan tersebut rawan banjir, khususnya saat hujan deras disertai dengan kondisi air pasang. Oleh sebab itu, studi ini dilakukan dengan tujuan mengkaji desain tanggul sebagai solusi penanganan banjir untuk kawasan tersebut. Kajian dilakukan berdasarkan simulasi banjir menggunakan model hidrodinamik NUFSAW2D untuk mengetahui pola genangan banjir kondisi eksisting. Dari hasil simulasi diketahui bahwa tanggul eksisting yang telah dibangun untuk Sungai Maen Besar mampu mengatasi banjir dengan kala ulang 2 tahun. Namun, kapasitas Sungai Maen Kecil tidak mampu mengalirkan debit banjir 2 tahunan sehingga menyebabkan banjir pada kawasan Desa Maen. Untuk kala ulang 25 tahun, kapasitas ketiga sungai tidak cukup untuk mengalirkan debit banjir. Untuk mengatasi masalah ini, penerapan sistem tanggul diusulkan, dimana tanggul eksisting yang berada pada sisi Sungai Maen Besar harus ditinggikan dan selanjutnya dibutuhkan pembangunan tanggul baru ke arah hulu. Sementara, sepanjang Sungai Maen Kecil tanggul baru harus dibangun. Hasil simulasi model NUFSAW2D menunjukkan bahwa dengan adanya sistem tanggul, kawasan Desa Maen menjadi aman terhadap banjir kala ulang 25 tahun. Selain itu, diperlukan dua kolam retensi untuk menangkap air hujan dari dalam kawasan Desa Maen untuk selanjutnya dialirkan kembali ke Sungai Maen Besar dan Sungai Maen Kecil. Hasil kajian dalam studi ini dapat dimanfaatkan oleh pemangku kepentingan (stakeholder) terkait dalam mewujudkan kawasan Desa Maen yang bebas banjir. Kata Kunci: banjir, Desa Maen, NUFSAW2D, tanggul

The Sub-watershed of Sampean Hulu, located on the slopes of Mount Raung is susceptible to erosion hazards. Erosion indicators have been observed in the irrigation channels, mainly due to frequent sedimentation, which compromises the irrigation infrastructure's optimization and water distribution. To address this, erosion monitoring using the Universal Soil Loss Erosion (USLE) model, along with GIS and remote sensing techniques, is essential. It was found that the irrigation networks associated with Clangap and Tamanan rain gauges are at higher risk due to intense rainfall. Maesan and Wonosari II rain gauges cover a larger irrigation network area, highlighting the need for erosion prevention measures. The dominant soil type, Tv, with a high clay content, is highly susceptible to erosion. Flat and gently sloping slopes have a lower risk compared to steeper slopes, while very steep and steep slopes pose higher erosion risks. Paddy fields and well-managed forest plantations have lower erosion hazards, while bare land and certain agricultural practices contribute to increased erosion risks. The analysis classified the erosion hazard into five classes, with the sub-watershed being predominantly low and very low susceptible to soil erosion. Implementing conservation practices, sustainable land management, and land use regulations are crucial for erosion prevention.

Raknamo Irrigation area (1323 ha) has problems with water availability, especially during the dry season, which causes a decrease in the productivity of the agricultural products from local communities. This is due to the suboptimal water distribution system in the Raknamo Reservoir. This study aims to analyze and optimize water distribution in the Raknamo Reservoir to obtain the most optimal water distribution to fulfill agricultural land's water needs in various seasons. Optimization analysis is carried out using a deterministic dynamic program. With this program, a complex and large-scale problem can be dispart into several small parts (decomposition), which are then optimized. Based on the analysis results, the maximum profit that can be obtained from the cropping intensity is 16% in the normal season. Meanwhile, the highest increase of the land area is 218.64 ha. It is worth noting that this study uses a deterministic dynamic program for optimization analysis to dispose of the complex problem into smaller, manageable parts. This approach facilitates a more systematic and comprehensive analysis and provides a framework for future decision-making processes related to water management and agricultural planning. The study's methodology and findings can serve as a valuable reference for similar water-related challenges in other irrigation areas, thereby contributing to the broader agricultural research and sustainable water resource management field.

Water offers many advantages that are essential for the preservation of human existence. Excessive quantities of water, such as flooding, can negatively impact human beings. The land utilization within a watershed (drainage area) plays a crucial role in the frequency and impact of flooding events. Instances of land use changes that resulted in flooding happened in the Bang Sub-watershed, located in Malang Regency. A comprehensive and up-to-date examination of flood management solutions is required. This study seeks to offer technical suggestions for flood management in the Bang Sub-watershed due to land-use alterations, utilizing the HEC-RAS software. Integrated treatment solutions are provided to mitigate the potential damage caused by future flooding. The flood simulation yielded recommendations for mitigating the impact of future floods. These recommendations include the construction of a retarding basin in the upper part of the river with a capacity of 1.4 million m3, as well as the construction of a 654 m long river embankment that is 50 cm. The alteration of the land leads to a decrease in the cross-sectional capacity of the river at the mouth of the Bang River, resulting in annual flooding occurrences. A non-technical approach to enhance the quality of the watershed is implementing reforestation measures to decrease the runoff coefficient.

This study aims to show that the Curve Number (CN) method can represent the relationship between rainfall runoff in the Temef Watershed, an area of ​​East Nusa Tenggara. The method used in this study was quantitative analysis by linking watershed characteristics such as soil, vegetation, and land use with the CN curve number, which shows the potential flow for a certain rainfall. CN data were re-analyzed using a computer program to obtain actual field conditions, which were then classified to obtain land cover quality, soil type, CN value, and Antecedent Moisture Condition (AMC) value for the Temef Watershed. Based on the study's results, it was found that the Temef Watershed was dominated by secondary dry land forest cover, which ranged from 28.50-52.00%. The lithological texture of rocks in the Temef Watershed is dominated by conglomerate and gravel with a gradation rate from medium to high; sandy marl, sandstone, tuft, and dacite of medium to a high gradation; and scaly clay with very low to low gradation. The CN value is 69.45, classified as medium gradation at normal soil moisture levels. The benefits of this result include the practical application of the CN method, the provision of accurate field conditions through re-analysis, insights into dominant land cover and lithological texture, and the establishment of CN values for effective water resource management.

The Kalimas River, managed by the Surabaya City Government for both eco-tourism and as a crucial water source for the Kalimas River basin residents, undergoes comprehensive examination in this study. The objectives encompass assessing water quality status, mapping its distribution, and forecasting waste discharge. Employing the Pollution Index and Water Quality Index methods, findings indicate that, according to the Polluter Index, the water quality predominantly falls within the lightly polluted category, ranging from 76.19% to 90.48%. Conversely, the NSF-WQI method portrays a more concerning picture, categorizing the Kalimas River’s water quality as heavily polluted within the same percentage range. As of 2021, the existing waste discharge stands at 0.392m3/s, serving a population of 233,563 people. Mapping results highlight a general trend of good water quality downstream, with the Upper Kalimas experiencing more compromised conditions. These revelations underscore the critical need for strategic interventions and environmentally conscious policies to address escalating pollution concerns. Ensuring the sustainability of the Kalimas River, pivotal as both a tourist attraction and vital water source, requires concerted efforts in pollution mitigation and water quality management. This study serves as a valuable foundation for informed decision-making in the pursuit of a healthier and more sustainable Kalimas River ecosystem.

The major floods that occurred in 2022 in Lhoksukon, North Aceh, Indonesia, had a severe impact on infrastructure damage and loss of life, making it necessary to analyze and predict its impact. In this regard, digital methods can effectively analyze and predict the impact of such natural disasters. The digital method is processing digital data through software to produce the desired information. Based on the results of the digital analysis, it has been found that the flood discharge in the Lhoksukon area of North Aceh is around 1848 m3/second with a flow velocity of about 3.484 m/second. This high flow velocity can cause significant damage to the infrastructure in the affected areas. The flood height in the river area ranges from 9.545 m from the riverbed, which is a cause for concern. The increase in water level will cause an expansion of the inundation area in the river area, which can lead to further damage. Therefore, the results of this study can be used to develop effective flood mitigation strategies and infrastructure planning in the affected areas. Additionally, the study's findings can be used to develop early warning systems to alert people in the affected areas to evacuate before the floods reach dangerous levels.

Controlling the concentration of Cr(VI) in industrial wastewater is imperative to adhere to environmental quality standards and mitigate the risk of polluting river waters, ensuring the safety of living organisms and public health. Acacia wood charcoal and coconut shell charcoal have emerged as effective adsorbents capable of reducing Cr(VI) levels. This research seeks to identify the optimal adsorption pH and evaluate the impact of initial adsorbate concentration on Cr(VI) removal, comparing the efficacy of acacia wood charcoal and coconut shell charcoal. The study systematically manipulated process variables, encompassing 2, 4, and 6 pH levels and adsorbate concentrations of 30, 40, and 50 ppm. Charcoal characterization techniques, such as XRF, FTIR, and SNI, were employed alongside analyzing Cr(VI) levels utilizing UV-visible spectrophotometry. Results elucidated that coconut shell charcoal exhibited a higher percentage removal of Cr(VI) at concentrations of 30% (41%), 40% (38%), and 50 ppm (31%), outperforming acacia wood charcoal, which displayed removal percentages of 16%, 14%, and 7%, respectively. Consequently, the research underscores the superior efficacy of coconut shell charcoal in Cr(VI) removal compared to acacia wood charcoal under the specified conditions. The findings contribute valuable insights to optimizing adsorption processes for industrial wastewater treatment, promoting sustainable practices and environmental stewardship.

The tsunami of June 3, 1994, which originated from a shift in the Indo-Australia plate, resulted in hundreds of casualties and material damage on the south coast of Jember. This study aims to understand the tidal impact of a tsunami in terms of arrival time and wave height. Several simulations of the interaction of tidal waves with tsunami waves were carried out through numerical modeling using Delft3D with modified wave characteristics from the Banyuwangi tsunami on June 3, 1994, as well as using bathymetry data from BATNAS and BIG tide data. The results of the analysis show that tidal waves can be a factor affecting the height of the tsunami waves. The increase in the amplitude of the tsunami waves was considered very local from the three observation points. This is shown at the observation locations of Puger Beach and Watu Ulo Beach, where the maximum wave amplitude occurs when the tsunami occurs independently of 7.102 m and 5.56 m, while at the Tanjung Pelindu observation location, the highest amplitude occurs when the tsunami meets the tides during low tide phase, which is 3.68 m. This research is expected to provide a basic understanding of the dynamic impact of the tidal wave when a tsunami occurs.

Road damage in the UB Forest Sumberwangi Area, Karangploso District, Malang Regency, is one of the harmful impacts of the drainage system. This study aims to analyze an accurate and efficient drainage system by applying modern methods, namely Building Information Modeling (BIM). By using BIM, the analysis of drainage work becomes faster and more accessible than with conventional methods. BIM is beneficial in building and analyzing drainage network data quickly and effectively and can help expand it to provide more accurate results. BIM can integrate models based on technical data and simulate development information into a three-dimensional model. BIM is used to perform 3D modeling of drainage channels using Autodesk Civil 3D, as well as analyzing channels from both hydrology and hydraulics with Storm and Sanitary Analysis (SSA). After calculating the design for a 5-year return period rainfall, channel dimensions of 50 x 50 cm and 30 x 30 cm were obtained. Based on the hydraulic analysis, it is known that several points have velocities that exceed the maximum velocity for the concrete surface (v < 3 m/s), so it is necessary to build a drop structure with h = 1 m. The quantity take off and the volume are calculated by Civil 3D for cut and fill work 7824.07 m3 and 1389.79 m3, respectively.

The construction of a check dam is proposed as a solution to address multiple environmental challenges in the upstream region of a river. Primarily, the focus is on erosion control, the deceleration of debris flow, and the prevention of sedimentation. The strategic implementation of this plan encompasses a range of methodologies, including topographical measurements, geotechnical testing, hydrological analysis, hydraulics analysis, and the meticulous development of a budget plan for the actual construction of the check dam. Within the study area, sedimentation issues stem from a debris flow characterized by a sediment discharge rate of 0.657 m3/s. This phenomenon coincides with a significant 25-year return period flood discharge of 9.134 m3/s. The proposed check dam emerges as a crucial intervention capable of effectively mitigating the situation for approximately 1 hour and 13 minutes, providing a targeted response to the persisting debris flow. To execute this plan, an estimated budget of IDR 460,859,000 has been projected. This financial allocation encompasses the expenses associated with topographical measurements, geotechnical testing, hydrological and hydraulics analyses, as well as the actual construction of the check dam. Overall, the proposed check dam stands as a multifaceted solution designed to harmonize environmental conservation with sustainable water resource management.

Pembangunan kawasan industri sebagai pusat kegiatan industri harus dilengkapi dengan sarana dan prasarana yang mendukung. Salah satunya adalah pembangunan kawasan industri di Cikarang, Kabupaten Bekasi, Jawa Barat. Studi ini bertujuan untuk merancang sistem drainase dan pengendalian banjir untuk menekan hidrograf banjir setelah pembangunan agar menyerupai kondisi eksisting saat sebelum dibangun. Studi ini dilakukan dengan menggunakan data hujan dari pos hujan Cikarang dan data hujan satelit GPM. Selanjutnya, analisis dilakukan dengan menggunakan dua metode, yaitu metode rasional dan pemodelan menggunakan program SWMM. Pada perencanaannya, sistem drainase kawasan dibagi menjadi dua saluran, yaitu saluran kiri dan kanan, yang keduanya dialirkan menuju saluran utama. Dimensi saluran direncanakan untuk dapat menampung curah hujan rencana periode ulang 2 tahun, dengan tinggi jagaan periode ulang 10 tahun. Berdasarkan hasil perhitungan dengan menggunakan metode rasional, dimensi yang diperoleh berkisar antara 0,2 x 0,2 m hingga 0,3 x 0,4 m untuk talang, 0,3 x 0,4 m hingga 1 x 1 m untuk saluran. Selanjutnya, dilakukan pemodelan menggunakan SWMM, di mana dimensi saluran dapat dioptimalisasi menjadi 0,3 x 0,3 m hingga 1 x 0,8 m. Hasil analisis menunjukkan bahwa perencanaan sistem drainase menggunakan pemodelan SWMM menghasilkan dimensi saluran yang lebih kecil dibandingkan dengan metode rasional. Disamping itu, terjadi peningkatan debit puncak dan volume limpasan, dengan angka peningkatan terbesar mencapai lebih dari 300% untuk curah hujan rencana periode ulang 2 tahun, karena adanya perubahan tata guna lahan akibat pembangunan kawasan. Untuk menanggulangi peningkatan tersebut, direncanakan dua kolam tampungan dengan luas 88 x 10 m yang dilengkapi dengan pompa. Kata Kunci: Alih fungsi lahan, metode rasional, pengendalian banjir perkotaan, sistem drainase, SWMM

Produktivitas pertanian dari lahan rawa yang ada di Indonesia tergolong masih belum maksimal. Salah satu penyebabnya adalah kurangnya pasokan air untuk irigasi pertanian. Dibutuhkan tindakan khusus agar sistem tata air di lahan rawa bisa mencukupi kebutuhan tanaman pertanian sepanjang tahun. Lokasi studi di lahan rawa yang termasuk ke dalam hidrotopografi B/C yaitu di Daerah Irigasi Rawa Danda Jaya di Provinsi Kalimantan Selatan. Tujuan dari penelitian adalah untuk mendesain sistem irigasi guna meningkatkan produktivitas tanam dengan menggunakan jaringan pompa irigasi di lahan rawa yang terpengaruh oleh pasang surut. Metode penelitian yang dilakukan meliputi analisis hidrotopografi, analisis hidrologi, analisis hidrolika, perhitungan pompa air dan pipa yang digunakan untuk irigasi. Hasil perhitungan menunjukkan kebutuhan air terbesar di lahan adalah 1,1 l/s/ha atau 73,5 l/s dengan pola tanam menggunakan 2 (dua) fase tanam. Saluran irigasi menggunakan saluran tertutup berupa pipa dengan ukuran antara 8 inchsampai 2,5 inch. Irigasi disuplay dari 2 unit pompa dengan kapasitas masing-masing adalah 40 l/s yang bisa dioperasikan secara terpisah untuk memenuhi kebutuhan air di lahan yang berada di sebelah kanan dan kiri saluran. Dalam desain tata air ini diperlukan 2 buah pintu air untuk menahan air pasang yang masuk ke dalam saluran tersier yang akan dimanfaatkan untuk kebutuhan irigasi. Selain itu, di dalam desain ini juga menggunakan pipa diameter 6 inchsebagai saluran pembuang untuk membuang kelebihan air di lahan persawahan ke saluran tersier. Kata kunci: pompa irigasi, hidrotopografi, pompa irigasi, jaringan pipa

Catatan sejarah dan kajian paleo-tsunami membuktikan bahwa siklus tsunami terjadi secara periodik di pesisir Aceh. Kesiapsiapsiagaan masyarakat dapat ditingkatkan dengan rencana tanggap darurat dan respon terhadap peringatan dini. Waktu evakuasi ditentukan oleh perkiraan waktu kedatangan (Estimated Times of Arrival, ETA) tsunami yang menjadi golden time dalam merespon tindakan selanjutnya setelah gempa. Estimasi waktu evakuasi menjadi penentu tingkat keberhasilan saat proses menyelamatkan diri dari kedatangan tsunami. Dengan demikian, tujuan penelitian ini adalah untuk memetakan ketersediaan waktu kritis bagi masyarakat di lokasi-lokasi tinjauan dalam merespon dan melakukan evakuasi setelah gempa terjadi. Pengamatan ETA dilakukan di utara pesisir Aceh, yaitu mencakup Banda Aceh dan Lhoknga juga pulau-pulau terluar sekitar; Pulau Weh, Pulau Nasi, dan Pulau Breuh. Makalah ini melakukan kajian tentang ETA yang dipicu oleh patahan Segmen Aceh-Andaman. Skenario skala gempa ditentukan sebesar 9,15 sebagai rekonstruksi Tsunami 2004 dan 9,2 Mw sebagai kondisi maksimum yang berpotensi terjadi. Pemodelan matematik tsunami dilakukan dengan model Nonlinear Shallow Water Equation (NSWE) dengan diskritisasi numeriknya diselesaikan berdasarkan Metode Beda Hingga skema eksplisit Leap Frog. Proyeksi waktu kedatangan tsunami di titik pengamatan ditentukan dengan fase-fase karakteristik kedatangan gelombangnya. Hasil pemodelan menunjukkan bahwa waktu kedatangan tsunami berdasarkan skenario yang ditentukan berkisar 18-22 menit untuk Sabang, 21-27 menit untuk Pulau Nasi dan Breuh, serta 34 menit untuk Banda Aceh dan Lhoknga. Pemetaan waktu kedatangan tsunami ini memberikan pengetahuan dalam perencanaan dan pengembangan sistem mitigasi tsunami khususnya dari aspek estimasi waktu dalam melakukan evakuasi menuju titik kumpul serta perencanaan jalur evakuasi dan jumlah maupun lokasi pembangunan bangunan evakuasi. Kata Kunci: hidrodinamika pantai, model numerik tsunami, tsunami arrival time, waktu evakuasi, mitigasi tsunami.

Tidal flood prediction is an important part of action plans in disaster mitigation. The lack of information about the time, duration and location of potential events in the pre-disaster stage, can lead to greater damage and losses. This study aims to fill the pre-disaster information gap by designing a short-term prediction system for tidal flood in the Pontianak City using one-way coupling model scheme. The scheme collaborates weather prediction model (WRF-ARF), hydrodynamic model (DELFT3D), and hydraulic model (HEC-RAS). The validation of the flood prediction map using the contingency table method by 67 survey points, indicates a good accuracy with a Hanssen-Kuipper Skill score = 0.77 – 0.91. Furthermore, based on the simulation, it was found that the potential for flood areas in Pontianak is around 15.10% - 16,03% of the city area. Hence, this area should be the focus for the local government to take preventive action to reduce the potential disasters in the future. Generally, this study has succeeded in integrating models in various dynamic aspects to predict tidal flood and the model framework can be recommended in tidal flood early warning systems. Keywords: Prediction; Tidal Flood; WRF-ARW; DELFT3D; HEC-RAS 2D; Pontianak

Gerusan di dasar sungai dapat menyebabkan longsor dan pengikisan pada tebing sungai. Longsor yang terjadi pada tebing sungai merupakan salah satu jenis longsor yang disebabkan oleh derasnya aliran sungai. Konstruksi penahan tanah dapat dibangun guna melindungi tebing sungai dari gerusan pada sungai dan menjaga stabilitas tanah, untuk itu perlu penelitian perancangan dinding penahan pada tebing sungai. Tujuan penelitian ini adalah untuk merencanakan dinding penahan tebing sungai yang aman terhadap stabilitas internal dan stabilitas eksternal. Metode penelitian dilakukan melalui perancangan penahan tanah dari blok beton segmental dengan perkuatan geosintetik berdasarkan data tanah di lokasi tebing sungai, tinggi tebing, dan kemiringan tebing sungai. Lokasi penelitian di Sungai Bah Bolon Kabupaten Simalungun Provinsi Sumatera Utara. Waktu penelitian dilakukan pada Maret 2021 sampai Juli 2021. Faktor keamanan dinding penahan dianalisis, baik terhadap stabilitas internal maupun terhadap eksternal. Hasil penelitian menunjukkan bahwa nilai sudut geser tanah merupakan parameter tanah yang penting diketahui dalam perancangan dinding penahan. Nilai faktor keamanan dinding semakin tinggi dengan semakin meningkatnya nilai sudut geser tanah. Perkuatan geosintetik semakin ekonomis dan dinding penahan tanah semakin stabil pada tanah yang memiliki nilai sudut geser yang semakin tinggi. Kata Kunci:Tebing sungai, dinding penahan, perkuatan geosintetik, stabilitas, beton segmental.

The elevation of the dam building foundation plan is at an elevation of +06.00 and +08.00, the results of sub-surface tests including the Standard Penetration Test (SPT) and Pressure Meter Test (PMT) show that at these elevations the SPT value is < 20 or categorized as loose rock and the PMT results shows a lateral pressure of 50 or in very dense rock layer, if the dam building foundation is still built at the elevation of the foundation plan, it can cause the building to become unstable due to the rock layer at that elevation not able to support the weight of the building. SPT values >50 was found at an elevation of +01.00 - -02.00 or 7 to 10 meters from the design elevation of the foundation. Furthermore, an analysis is carried out based on the results of sub-surface test to determine the method of strengthen the foundation. The results of the analysis show that the bore pile foundation is effective as a method of foundation strengthen. The analysis includes the analysis of the ultimate bearing capacity, the axial allowance bearing capacity of the pile foundation and the bearing capacity of the pile group foundation. Based on the analysis, strengthening the foundation of intake area requires 156 piles with a depth of 19 meters, the spillway area requires 196 piles with a depth of 17 meters and the retaining wall area requires 64 piles with a depth of 15 meters. Keywords: Sub-surface test; alluvial sand; tuffaceous sandstone; bore pile; bearing capacity

Concrete gravity dams continued to develop in Indonesia even though the population is still smaller than embankment dams. Until 2021 there consist of 16 concrete gravity dams or about 7% of all dams in Indonesia. The utilization of concrete gravity dams in Indonesia is 75% for hydropower or as many as 12 dams. Concrete gravity dam is a high-risk structure so the design of concrete gravity dams must be referred to the guidelines where applicable in Indonesia and internationally with approval from Dam Safety Organization. In Indonesia, the construction of concrete gravity dams cannot be separated from the participation of design consultants from developed countries such as the UK, Japan, US, Canada, Korea, and China. Indonesian Water Resource Guidelines 2009 is formal reference that must be adhered to by all design and construction planners in Indonesia, so that designs that refer to the guidelines and manuals from foreign countries must go through a comparison and evaluation process to meet the design acceptance criteria in accordance with the Indonesian Water Resource Guidelines 2009. Comparison processes include load conditions, design concepts, seismic analysis methods, stability and stress analysis methods, and stability and stress acceptance criteria. As a results of comparison, we can get information that the Indonesian Water Resource Guidelines 2009 apply stability and stress acceptance criteria more conservative. As consequence, the investment cost for the construction of concrete gravity dams in Indonesia is becoming more expensive. Keywords: dams, concrete gravity, guidelines, comparation, stability.

In order to create calm ocean water, breakwater is essential for reducing wave energy. Rubble-mound breakwater with tetrapod and dolosse armor can be a solution in reducing ocean wave energy. This research aims to understand the effectiveness of rubble-mound tetrapod and dolosse breakwater in reducing wave energy with sea level condition variation in a laboratory. The method of this research is an experimental method that uses a breakwater physical model with various scenarios. Testing scenarios are determined based on water depth, wave period (T), and armour structure. The results of this research showed that rubble-mound tetrapod breakwater is the most effective breakwater with an average reducing percentage of 86.7%. Rubble- mound tetrapod and dolosse breakwater physical model have high effectiveness because they are built by rubble mound structure that forms a sloping side. These structures are effective in reducing wave energy because the waves get in between rock slits. So, the wave energy reduces when it passes through the breakwater. This research can give some information and analysis in planning a breakwater effectively and efficiently in the ocean. Keywords: breakwater physical model, tetrapod, dolosse, wave energy

The presence of hydraulic jumps downstream of the weir structure is a natural occurrence that indicates a change in supercritical to subcritical flow characteristics. Hydraulic jump is one indicator of the dissipation of energy in the stilling basin. Therefore, the absence of a hydraulic jump can be a problem for some weirs, as happened in the Cikeusik Weir, which experienced damage to the stilling pool floor so that the energy dissipation did not function optimally. This paper will discuss the potential causes of damage to the Cikeusik weir and alternative designs for its countermeasures. A physical model test was carried out in the laboratory with a scale of 1: 40 to obtain an appropriate alternative to the stilling pond design for the Cikeusik weir. The tests were carried out with variations in the discharge Q2 years, Q25 years, and Q100 years, respectively. Three model tests were conducted, namely the existing and two modified designs. Based on the model testing results, extending stilling basin floor length with a dentated end sill and adding downstream riprap is the most optimal alternative because it has an energy reduction effectiveness of up to 80% and the lowest downstream scour potential compared to other options. The results of this test are expected not only to be used as an alternative to mitigate the damage to the Cikeusik weir but also to other locations that have similar problems. Keywords : Cikeusik Weir, stilling basin, Froude number, local scour, physical model

The 2004 Indian Ocean Tsunami, which devastated the coasts of Aceh and Nias, revealed that the event was a mega-hazard category. Following the disaster, a new era in the development of tsunami mitigation throughout the archipelago began. Nonetheless, given the impact of the two tsunamis that occurred at the end of 2018, achieving mitigation within 17 years poses a unique challenge and high priority. The relationship between tsunami-prone areas and community preparedness has become a crucial factor in achieving regional disaster resilience. The objective of this research is to provide a regional assessment of tsunamis risk as well as community preparedness for future tsunami. The coast of Teluk Ulee Lheue, Aceh Besar, was chosen as the location for the assessment as a role model. The research method consists of tsunami mathematical modeling considering the impact caused by the magnitude of earthquakes 8.2, 9.15, and 9.2. The Nonlinear Shallow Water Equation (NSWE) model was used in the simulation, which was discretized using the explicit leap-frog Finite Difference Method. Field activities were included not only to collect topography and land use data but also to gather information and community response. The data was provided directly from the local community through the completion of a questionnaire, with a total of 150 respondents being evaluated. The findings of this study reveal that the consequences of the tsunami inundation remain quite considerable, even for a smaller-scale earthquake than the previous 2004 event. In general, the degree of community preparedness seems to be quite high, especially in terms of tsunami awareness. An improvement in disaster emergencies is required, specifically in the household sector. However, with a high degree of community preparedness, it would be essential to carry out individual evacuations rapidly. Keywords: tsunami hydrodynamics, numerical simulation, run-up, community preparedness, environmental social

Penelitian ini bertujuan untuk memperoleh data curah hujan dari TRMM dan pos hujan yang dapat dipakai pada analisis hidrologi. Analisis ini dilakukan pada 24 data pos hujan yang dikunci oleh grid TRMM dengan resolusi 0,25° x 0,25°. Dalam setiap grid TRMM terdapat minimal 1 data pos hujan sehingga berdasarkan persebarannya pada penelitian ini terdapat 8 grid TRMM. Hasil yang diperoleh adalah nilai koefisien korelasi pada basis hujan bulanan sebesar 0,3218 – 0,9351. Nilai RMSE pada basis hujan bulanan sebesar 69,46 – 856,25. Nilai error pada basis hujan harian maksimum tahunan (HHMT) sebesar 0,0597 – 1,1138. Nilai error pada basis hujan harian sebesar 0,0023 – 0,0321. Data curah hujan yang lolos uji karakteristik hujan rencana ialah data yang memiliki nilai R100/R2 antara 1,5–3,4 serta grafik lengkung faktor pertumbuhannya memiliki trend yang relatif sama dengan data hujan lainnya. Data satelit yang lolos uji karakteristik hujan rencana ialah yakni TRMM I, II, III, IV, V, VI dan VIII. Pos hujan yang lolos uji karakteristik hujan rencana yakni Nifukani, Nule, Kesetnana, Oinlasi, Tilong, Lasiana, Penfui, Tarus, Oeletsala, Naibonat, Tubutesbatan, Raknamo, Camplong, Batuliti, dan Baun.

The main occupation of residents who live in Abab Sub-Watershed, Blitar Regency, is as farmers in agriculture and plantations. Agriculture and plantations need rain data that have been calculated to maximize the yields to be obtained. Hydrometeorological disasters, specifically floods, often occur at this location. Therefore, research is needed on calculating design rainfall, outlined in easy-to-understand isohyet maps. The research aims to assist the planning of water structures or other hydrological research without having to recalculate or retest data from the beginning. This study's utilized return periods were 2, 5, 10, and 25 years, plotted as isohyet maps. Before calculating the design rainfall, the rainfall data had to be tested first. Calculation of design rainfall used SMADA Distrib 2.13 application and was tested with the distribution suitability test. The results of the distribution suitability test showed that Log Normal is appropriate to be used. The results of plotting the design rainfall on an isohyet map using the IDW, Kriging, and Spline methods showed that the IDW and Spline maps are smoother and not as broken as Kriging. Next, a comparative analysis of RMSE and NSE was carried out. For return periods of 2, 5, 10, and 25 years, IDW has the smallest RMSE mean value of 0.016 and the highest NSE average value of 0.9999.

A reservoir is a place to store river water formed by the construction of a dam. The main problem of reduced water quality for Selorejo Reservoir is caused by the inflow of water from livestock, agricultural, and household wastes containing high amounts of nitrates and phosphates. The objective of this study is to determine the water quality status of Selorejo Reservoir using the DOE-WQI, Pollution Index, DWQI, Ved Prakash Index, and Prati Index methods; to find out the distribution of characteristics for water quality status using the IDW method and to find out the capacity of water pollution load for Selorejo Reservoir using Total-P. The research showed that the characteristics of water contamination for Selorejo Reservoir in 6 years indicate light pollution. Through the DWQI method, the contamination percentage became smaller downstream, while the DOE-WQI, Pollution Index, Ved Prakash Index, and Prati Index methods showed the opposite results. Total-P levels in the 2021 dry season were 42.475 mg/m3 (upstream), 35.767 mg/m3 (middle), and 37.567 mg/m3 (downstream). The pollution load capacity is 71.77 mg/m3 (upstream), 80.14 mg/m3 (middle), and 77.9 mg/m3 (downstream). It can thus be said that Selorejo Reservoir is still within the maximum reservoir pollution load limit.

Selorejo Reservoir is used for flood control activities, hydropower, agricultural irrigation, fisheries, and tourism. In 2021, the water quality of Selorejo Reservoir worsened, which was indicated by fish mortality and an increase of water lettuce plants; the decline in water quality of Selorejo Reservoir may be due to agricultural and farming waste that was carried by surface runoff and entered the reservoir. This study was conducted to determine the status of water quality in Selorejo Reservoir using the Pollution Index, Oregon-WQI, CCME-WQI, and NFS-WQI methods in the dry season based on the parameters of pH, BOD, COD, DO, TSS, Nitrates, Ammonia, Phosphate, and fecal coliform. Based on the Pollution Index method, the water quality was in the "Slightly Polluted" condition. The Oregon-WQI method indicated the "Severely Polluted" condition. The CCME-WQI method indicated the "Good" condition. The NSF-WQI method indicated the "Fair" condition. The trophic status of Selorejo Reservoir was found to be eutrophic, with high levels of phosphorus. Calculation of the pollution carrying capacity based on the Total-P of the dry season in 2021 showed that the upstream, middle, and downstream parts of the reservoir are respectively able to accommodate 71.77 mg/m3, 80.14 mg/m3, and 77.90 mg/m3.