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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.

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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.

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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.