Author(s): Kentaro Aoki, Masaharu Fujita
Linked Author(s): Kentaro AOKI
Keywords: Flood defense forests, flooding water, flood control effectiveness, lodging flood defense forests, velocity of floodplain
Abstract: The Gounokawa River has the maximum basin area in the Chugoku region, with its lower reaches located in the Shimane Prefecture in Japan. In the lower reaches of the Gounokawa River, many districts without dikes exist, and the degree of river improvement security is low. In addition, it is expected that the local population will decrease by more than 30% in the next 30 years. Therefore, it is difficult to construct dikes with a degree of progress similar to that in the past. However, bamboo trees planted as flood reduction measures still remain as flood defense forests. Therefore, in the lower reaches of the Gounokawa River, it is important to utilize the flood defense forests for river security improvement. Flood water depths are high, and early velocity acts on the flood defense forests, which may be lodged and washed away. However, these risks have not been considered for large-scale flooding. In this study, we built a numerical analysis model (2-D shallow-water flow model) capable of quantitatively calculate river improvement effects and lodging of flood defense forests. We evaluated the lodging of flood defense forests based on the bending moment acting on them at the time of flooding. We performed a quantitative evaluation of the river improvement effect of the flood defense forests in the lower reaches of the Gounokawa River and examined the maintenance policy utilized for river improvement effects. In addition, based on our assumptions about lodging flood defense forests at the time of large-scale flooding, we considered differences due to floodplain velocity
Year: 2017