Author(s): Hendra Ramdhani; Takeyoshi Chibana; Agus Santoso
Linked Author(s):
Keywords: Meandering River; Aspect Ratio; Sinuosity; Sediment; Geology
Abstract: Forming mechanism of meandering river is diverse and complex. Investigation of cross -sectional aspect ratio (width to depth ratio) and its variation could help to comprehend such mechanism. Cimanuk River as one of main rivers in West Java, Indonesia, was selected as main focus to study the relationship between meandering parameters and cross-sectional aspect ratio. The river has an interesting characteristic that could explain several possibilities of meandering processes. The results have shown that meandering mechanism in Cimanuk River might be affected by less variation of cross-sectional aspect ratio in the flow direction, but still has moderate to high sinuosity. Several curving reaches exist in meandering plain, but have less changing channel centerline for the past 10 years. Other meandering rivers, however, have large variation of aspect ratio that is closely related to the river widening caused by bank erosions. Geologically, meandering plain in Cimanuk River might be formed around subduction zone in the northern part of Java Island. Deposition and sedimentation process are dominant in this plain. A wider coastal deposition area could also be found in this region. In such a low and flat area, sand as bed material presents as a result from the volcanism and river sedimentation process. In some curving reaches, sand bars were found, but it has less impact to planform change because of stable bank that is composed of fine material. Meandering processes in the lower reaches of Cimanuk River might be less active due to the lack of coarser material. In other unstable meandering rivers, fine or medium gravel are contained, and gravel bar can be formed in wider channel where the aspect ratio is more than 25.
Year: 2020