洪水営力による樹木管理後の幼木林動態を踏まえた樹林化抑制手法の考察

Abstract

Gravel-bed rivers in Japan are now facing a multitude of problems relating to fluvial environment and flood control. These problems include the expansion of river beds with less disturbance by flooding and the growth of the riverine trees and the decrease of high-quality gravel-bed bars and the immobilization of low-flow channel. In particular, the gravel bed river that dominated by vigorous growth of Willows and Robinia pseudo-acacia, sometimes increase the riverine trees by vegetative propagation under the flood disturbance. In addition, expansion of the overgrowth density is likely to occur as the young riverine trees that easily fallen by flood disturbance. In this study, to target the gravel bed of Watarase river that Robinia pseudo-acacia, etc. grows in the river, evaluated the dynamics of young riverine trees after felling, and proposed the excavation shape of gravel-bed bar for forestation suppressing by using flood disturbance.