Study of Erosion Control Techniques Applied to Hydroelectric Power Plants Reservoir Margins

Abstract

This paper aims to provide relevant results of research performed on erosion control processes at water reservoir margins under tropical conditions. This large-scale streambank erosion control study is located on the margins of the water reservoir at Volta Grande Hydroelectric Power Plant in Brazil. This reservoir lake occupies an area of 220 km2, and is located in the border of the states of Minas Gerais and São Paulo. Three experimental sites, with fast bank retreat, were identified for the implementation of these erosion control works: Pier (2,700 m2), Baia (3,524 m2), and Miguelopolis (1,280 m2), in a total study area of 7,500 m2 and length of 500 m, around the reservoir lake. Eleven different bioengineering treatment techniques, vegetated and armored techniques, were implemented on 27 parcels on these three study-areas, as follows: Straw logs and Coir logs (biologs); three metallic gabions coated with polymers and PVC-bags, box, and mattress; Polypropylene (PP) P550 geotextile; PP geotextile C350; Sintemax geotextile; MacMat geotextile; and wood crib wall. Laboratorial and field testings and measuremnents included geotechnical studies, fertility, turbidity, wind velocity, wave height, stratigraphy of the study area, and in situ permeability. All obtained geotechnical results pointed that the streambank soil is erosion prone. Collected data over a period of three years were summarized in a Performance Matrix. Turbitidy, wave height and wind velocity measurements were difficult to correlate, and could not provide much information on soil loss. Thus, to gather more data on the sediment acumulated in front of each treatment, differential bathymetry was performed and plotted by using ArcGIS map algebra. Under the studied conditions, the best biotechnical methods were armored techniques such as Gabion mattress associated with geotextile, and rip rap associated with Gabion mattress, whereas vegetated biologs and crib walls had the worst performance. Also, the use of vegetation soley was not an efficient method for controlling erosion.

Semi-Rigid Erosion Control Techniques with Geotextiles Applied to Reservoir Margins in Hydroelectric Power Plants, Brazil

“…The climate of the study areas is classified as Cwa, with dry winters and hot summers, according to the Koppen climate classification [24]. With a dry season from April to September and 80% of the rainy season lasting from October to March [25] [26], the soil of the two experimental units is sandy silt (ML).…”

“…Monitoring occurred periodically, with monthly visits up to 2020. The performance of the techniques was analyzed qualitatively, adopting the performance matrix used by Galvão et al [25]. The variables shown in Table 4 were considered where each variable has a weight (from 0 to 3).…”