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1

Soil erosion rate and hazard level at the Sianjo-anjo Reservoir watershed in Indonesia

Gusma Felia, Azmeri Azmeri, Jemi Faris Z., Rahmatan Hafnati

Journal of Water and Land Development

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2023

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no. 57

181--187

EN

The Sianjo-anjo reservoir is used to meet the need for downstream clean water. Land activity at the Sianjo-anjo reservoir watershed can potentially increase the rate of erosion and the silting of rivers and reservoirs due to sedimentation. Reservoir siltation is a crucial challenge for reservoir management because it can reduce its function and affect its service life. However, sediment yield is often overlooked in reservoir planning and environmental assessment. This study aims to predict the rate of land erosion and sediment yield, and create an erosion hazard map of the Sianjo-anjo reservoir watershed. The study used a Geographic Information System, GIS-based Universal Soil Loss Equation (USLE) method and discovered that the erosion rate of the Sianjo-anjo reservoir watershed was between 35.23 Mg∙ha-1∙y-1 until 455.08 Mg∙ha-1∙y-1, with 95.85% classified as the low level, 0.03% as moderate, and 4.12% as high. Meanwhile, the sediment yield from the Sianjo-anjo reservoir watershed was 218,812.802 Mg∙y-1. USLE is vital to identify areas susceptible to erosion and crucial for reservoir sustainability. Furthermore, it is necessary to plan good sediment management. Long-term land conservation is required to maintain storage capacity and ensure effective operation of the reservoir.

2

Cross-waves and pulsating flows in the side-channel spillway - an experimental approach

Azmeri Azmeri, Ummah Chairatun, Jemi Faris Zahran, Faudli Imam, Nasaiy Qurratul 'Aini Benti

Journal of Water and Land Development

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2023

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no. 56

51--57

EN

Potentially hazardous side-channels of complex geometry need to be investigated using detailed hydraulic physical models. This study aims to analyse the cross-waves pattern and pulsating flow using a side-channel spillway physical model. This study compares the cross-waves pattern were measured using an experimental installation set to generate cross-waves on the surface (original series) with another structure that did not produce cross-waves (modified series). The results showed that the geometry of the left wall caused instability in flow patterns and secondary flows. The starting point of Q2 discharge was detected by minor turbulence on the water surface near the left wall at a water depth of 3.3 m at the starting point of the wall, but with no overtopping. Cross-waves formed downstream at the right wall crosswise, lower than at the left wall. The height of the cross-wave increased substantially from Q100 to Q1000 discharges leading to overtoppings near the left wall at a water depths of 4.2 and 5.0 m at the starting point of the wall, and near the right wall at a water depths of 3.8 and 4.0 m at the upstream point of the wall. The modifications provided optimal hydraulic conditions, i.e. elimination of cross-waves and non-uniform flows. The Vedernikov and Montouri numbers showed that both original and modified series did not enter the area where the pulsating flow occurred. This indicated that both series were free from the pulsating flow.

3

The eco-hydraulics base as flood mitigation to overcome erosion and sedimentation problems : a case study in the Lae Kombih River, Indonesia

Ziana Ziana, Azmeri Azmeri, Yulianur Alfiansyah, Meilianda Ella

Journal of Water and Land Development

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2022

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no. 55

229--239

EN

Erosion and sedimentation have a very big influence on flooding. Floods are strongly influenced by land use and population activities that change the river’s physical condition, including erosion and sedimentation. The river upstream was very steep, and the downstream was narrowing and meandering with high rainfall recorded. This study analyses erosion, sedimentation, and its handling using the eco-hydraulic base. The method involves input rainfall data, river hydraulics, land use, watershed area, and land cover. The analysis of hydrology, hydraulics, land use, flood discharge, and eco-hydraulic, inundation height, vegetation diameter, velocity reduced, and riverbank width measured in five bridges cross-sections along the river. The eco-hydraulic compares the width of existing riverbanks and design, high inundation, and the vegetation diameter to minimise flood discharge. Erosion in the right cliff is 22.73% and the left cliff is 37.04%, land erosion was 225.83 Mg∙ha-1∙year -1. The river’s bottom is formed by rocks of 0.18-1.30 mm. The plantation land used around the Lae Kombih River grows mainly an oil palm with a diameter of 0.5-0.7 m. The riverbank design on 100 m for vegetation diameter of 0.1-1.0 m can retain flood discharge for five years return period up to 72.3%, resulting in discharge of 112.04209.43 m3∙s-1. The largest erosion and sedimentation on the river border is Dusun Silak, so it is recommended to plant Vetiveria zizanioides, Ipomoea carnea and Bambusoideae. An inundation height of 0.9 m can be recommended to design an embankment to be used as flood mitigation.

4

Surface erosion hazard and sediment yield for Keuliling Reservoir in Indonesia

Azmeri Azmeri, Nurbaiti Nurbaiti, Mawaddah Nurul, Yunita Halida, Jemi Faris Zahran, Sundary Devi

Journal of Water and Land Development

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2022

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no. 52

108--118

EN

The construction of the Keuliling Reservoir aims to accommodate and utilise water for agricultural purposes. In this research, soil erosion modelling using the USLE method showed that the level of erosion hazard for each Keuliling Reservoir sub-watershed was classified into low-moderate. Land erosion occurred in the area around the reservoir inundation is the most significant contribution to the magnitude of erosion (38.62Mg∙ha-1y-1. Based on the point of sediment sampling in the Keuliling reservoir, the sediment volume was 1.43 Mg∙m-3. So, the volumetric sediment input from the Keuliling reservoir watershed is 20.918,32 m3∙y-1. The degradation of reservoir function due to sedimentation can affect reservoir services. The ability to estimate the rate of watershed surface erosion and sediment deposition in the reservoir is vital for reservoir sustainability. Besides the land erosion in the Keuliling Reservoir, there are also other potential sources of erosion that can reduce the capacity of the reservoir, i.e. the rate of sedimentation from a reservoir cliff landslide. The USLE estimation results show that the soil erosion analysis provides important and systematic information about nature, intensity and spatial distribution in the watershed and sediment volume in the Keuliling Reservoir. This finding allows the identification of the most vulnerable areas and the type of erosion dominant for long-term land management.

5

An experiment of energy dissipation on USBR IV stilling basin - Alternative in modification

Bantacut Alfiansyah Yulianur, Azmeri Azmeri, Jemi Faris Zahran, Ziana Ziana, Muslem Muslem

Journal of Water and Land Development

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2022

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no. 53

68--72

EN

Previous researchers have been widely studied the equation for calculating the energy dissipation in USBR Type IV, applied in the stilling basin structure as an energy dissipator. However, inefficient energy dissipating basins are commonly found in the field due to the large discharge and high water head, potentially damaging the bottom of the energy dissipating basin and its downstream river. Therefore, an energy dissipator plan fulfilling the safe specifications for the flow behaviour that occurred is required. This study aimed to determine the variation of the energy dissipators and evaluate their effect on the hydraulic jump and energy dissipation. For this purpose, a physical model was undertaken on the USBR Type IV spillway system. The novelty of this experiment showed that combination and modification dissipation features, such as floor elevation, end threshold and riprap lengthening, could effectively dissipate the impact of energy downstream. The final series exhibited a significantly higher Lj/y1 ratio, a favourable condition due to the compaction of the hydraulic jump. There was also a significant increase in the downstream tailwater depth (y2) during the jump formation. Therefore, the final series energy dissipator was better in the stilling basin design for hydraulic jump stability and compaction. The increase in energy dissipation for the final series type was the highest (98.4%) in Q2 and the lowest (84.8%) in Q10 compared to the original series. Therefore, this type can better reduce the cavitation risk damaging to the structure and downstream of the river.

6

Hydraulic jump and energy dissipation with stepped weir

Azmeri Azmeri, Basri Hairul, Yulianur Alfiansyah, Ziana Ziana, Jemi Faris Zahran, Rahmah Ridha Aulia

Journal of Water and Land Development

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2021

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no. 51

56--61

EN

Energy dissipator functions to dissipate the river-flow energy to avoid longitudinal damage to the downstream river morphology. An optimal energy dissipator planning is essential to fulfilling safe specifications regarding flow behavior. This study aims to determine the variation of energy dissipators and evaluate its effect on the hydraulic jump and energy dissipation. For this purpose, a physical model was carried out on the existing weir condition (two steps). It was also carried out on four stepped-weir variations, i.e., three-step, three-step with additional baffle blocks at the end sills, four-step, and six-step. Dimensional analysis was employed to correlate the different parameters that affect the studied phenomenon. The study shows a three-step jump shows a significantly higher Lj/y1 ratio, which is an advantage to hydraulic jumps’ compaction. The comparison of energy dissipation in all weir variations shows that the three-stepped weir has wasted more energy than other types. The energy dissipation increase of the three-step type is 20.41% higher than the existing type’s energy dissipation and much higher than other types. The dimensions of the energy dissipation basin are the ratio of the width and height of the stairs (l/h) of the three-step type (2.50). Therefore, this type is more optimal to reduce the cavitation risk, which damages the river structure and downstream area.

7

Physical vulnerability to flood inundation: As the mitigation strategies design

Azmeri Azmeri, Yunita Halida, Safrida Safrida, Satria Indra, Jemi Faris Z.

Journal of Water and Land Development

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2020

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no. 46

20--28

EN

Flood with intense rainfall and inadequate drainage system leads to flood inundation in residential areas, which in turn damages the housing components and causes a loss. The different level of flood inundation at various affected locations caused varying degrees of losses. This study aimed to identify the damage conditions and analysed the physical loss of the residential building components. The physical vulnerability level is influenced by two damage qualification: the structural and architectural damages. The third-order polynomial function approach produces the best model for both qualifications, yielding the smallest average of errors (RMSE) of 0.0187 for the structural quality and 0.0672 for the architectural quality. The amount of losses related to the architectural elements of the house is smaller compared to the structural one as it is not its main component. This approach is useful as a guide in determining the post-flood handling rehabilitation cost of both structural and architectural elements that will be more appropriate for future conditions. This information is essential as effective management to design flood disaster mitigation strategies and may serve as a basis for flood risk management.

8

Effects of irrigation performance on water balance: Krueng Baro Irrigation Scheme (Aceh-Indonesia) as a case study

Azmeri Azmeri, Yulianur Alfiansyah, Zahrati Uli, Faudli Imam

Journal of Water and Land Development

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2019

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no. 42

12--20

EN

Krueng Baro Irrigation is focused on increasing the productivity of food crops in Pidie District, Aceh Province, Indonesia. However, due to the age of the irrigation infrastructure (more than 30 years) and its large networks, it is necessary to investigate the actual water conveyance efficiency. This study aimed to evaluate the conveyance efficiency of primary and secondary channels of the irrigation system, as well as to create a water balance model based on the actual water conveyance efficiency. The model by using Excel Solver with its objective function is to maximize the area of the irrigated land. Based on the optimization model of the water balance, the design condition can irrigate an area of 9,496 ha (paddy-I), 4,818 ha (paddy-II), and 11,950 ha (onion). The measurement results reported that the actual efficiency of Baro Kanan and Baro Kiri was 56% and 48% smaller compared to the efficiency of the designs (65%). The water loss was due to the damage to the channel lining and channel erosion resulting in the high sedimentation, leakage, and illegal water tapping. These lead to a decrease in the area of the irrigated land. Based on the optimization model of the actual water balance, the irrigated land was reduced to 7,876 ha (paddy I) and 3,997 ha (paddy-II) while it remained the same for onion. Therefore, to increase the efficiency, the regular maintenance and operations are required by fixing the damaged irrigation structure and channels, the maintenance of sedimentation, and the strict regulation of illegal water tapping.

PL

Nawodnienia Krueng Baro służą zwiększeniu produktywności upraw w dystrykcie Pidie w prowincji Aceh, Indonezja. Z powodu wieku infrastruktury irygacyjnej (ponad 30 lat) i rozległej sieci nawodnień konieczne jest zbadanie obecnej efektywności transportu wody. Przedstawione badania miały na celu ocenę efektywności transportu wody w kanałach pierwszego i drugiego rzędu w systemie irygacyjnym oraz stworzenie modelu bilansu wody na podstawie uzyskanych aktualnych danych. Z optymalizacyjnego modelu bilansu wodnego wynika, że zaprojektowany system może nawadniać 9 496 ha (pole ryżowe I), 4 818 ha (pole ryżowe II) oraz 11 950 ha (cebula). Wyniki pomiarów wskazują, że rzeczywista efektywność systemów Baro Kanan i Baro Kiri była mniejsza odpowiednio o 56% i 48% od efektywności projektowanej (65%). Straty wody wynikały z uszkodzeń umocnień kanałów, erozji skutkującej dużą sedymentacją, przecieków i nielegalnych ujęć wody. Te czynniki spowodowały zmniejszenie powierzchni nawadnianych pól. Na podstawie wyników uzyskanych w modelu optymalizacyjnym rzeczywistego bilansu wodnego powierzchnię nawadnianych pól zmniejszono do 7 876 ha (pole ryżowe I) i 3 997 ha (pole ryżowe II). Powierzchnia nawodnień obiektu „cebula” pozostała bez zmian. Aby zwiększyć efektywność, konieczne są regularne działania naprawcze uszkodzonej struktury irygacyjnej, zatrzymanie sedymentacji i ścisła kontrola nielegalnego poboru wody.