| Erosion


due to the high cost of the work. And when measures are implemented, they typically involve conventional technical approaches such as gabions, stone settlements, concrete, soil cement, and geotextiles. With the above in mind, the authors say the search for environmentally friendly, economically viable, and sustainable technical solutions has gained importance in recent years, with soil and water bioengineering techniques offering a viable alternative. Taking into account both technical and environmental factors, these techniques mostly use living materials (seeds, plants, plant parts, etc.) that can be combined with inert materials.


In their study, the authors investigated four different types of soil and water bioengineering measures to stabilise and control erosion processes on the banks of hydroelectric reservoirs. The study area focused on the reservoir of the Ita hydroelectric power plant on the Uruguay River in southern Brazil. The proposed nature-based solutions aim to cover


and protect the banks with native rheophyte plant species that were naturally present on the banks of the Uruguay River before the power plant was built. Techniques designed for the upper slope included coconut bioretention, wooden bank pile wall and enveloped soil – all of which proved effective in stabilising and protecting the base of reservoir’s water level. While techniques designed for the lower slope included live siltation, square planting, wooden palisades and coconut bioretention. These acted as living physical barriers against the action of waves, dissipating their kinetic energy. Even after a short time of data collection, and the focus of what has been called a very empirical approach, the authors say their results show that such natural engineering techniques offer innovative and technically feasible solutions for rehabilitation projects in the vicinity of hydroelectric dams, and can be used independently or in addition to conventional engineering techniques. They go on to add their use offers additional ecological, economic, environmental and aesthetic benefits in addition to the intended technical effects.


Admitting that these effects will change over time


due to the evolution of plants, the authors conclude it is essential to have a longer period of data, of vegetation, erosion and load, to have more secured results and develop numerical models to optimise such bioengineering efforts against these specific erosion processes.


Indonesian experience Studies into erosion and sedimentation have also been


carried out at Indonesia’s Batujai Dam and are being used to not only help determine the magnitude of the problem, but provide future reference for controlling and maintaining the reservoir. Batujai Dam is the largest dam in Central Lombok. At the beginning of its construction in the late 1970s, the reservoir had a depth of 18m. By 2019 it decreased to 12m, with more than 35% of the surface covered by water hyacinths, causing reservoir capacity to fall from 25Mm3


to 18.4Mm3 . Land degradation due to erosion in the watershed


area upstream of the reservoir is believed to have contributed significantly to such high sedimentation rates, compounded by the presence of the water


hyacinths. And although the government has carried out sediment dredging to increase reservoir capacity, it hasn’t yielded good results.


A study carried out by Utari et al in the Asian Journal of Engineering, Social and Health estimated the magnitude of erosion at this Indonesian reservoir. They used the Universal Soil Loss Equation (USLE) which is a parametric model used to predict erosion from a land area, and the Modified Universal Soil Loss Equation (MUSLE) – an extension of the former model which replaces the rainfall erosivity factor with the surface runoff factor. After successfully identifying the level of erosion and sedimentation in the Batujai reservoir, the researchers determined that factors such as rainfall erosivity, soil type, slope length and slope, and land use and soil vegetation directly influence the increase in erosion rates. Erosion also tends to be low in areas with gentle slopes and dense vegetation cover. It was also suggested that for any future research,


existing erosion values can be used and grouped into erosion hazard classes, so that subsequent conservation actions can also be determined based on areas with high erosion.


Morocco


Another study conducted in the Chichaoua watershed in the High Atlas Mountains of Morocco, aimed to quantify soil loss, investigate its causes, and evaluate its effects on the construction of the new Boulaouane dam. Situated southwest of Marrakech city, the Chichaoua basin covers an area of 2696km2


and is drained by the


Oued Chichaoua, along with its tributaries, the Oued Imintanout and the Oued Seksaoua. In their research, Baiddah et al were able to quantify


potential soil losses and show they exceeded tolerance thresholds. With results indicating that the watershed substantially contributes to downstream sediment loads, the authors say this could impact the hydrological performance and lifespan of the Boulaouane dam.


Highlighting the critical need for implementing


erosion control measures, especially in upstream areas, this study in Ecological Engineering and Environmental Technology, suggests intense


www.waterpowermagazine.com | November 2025 | 19


Above: Fisherman at the Batujai Dam in Indonesia


Below: Groundhog infestation can lead to problematic erosion in dams


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