STUDY ON THE IMPROVEMENT OF FLOOD MITIGATION FUNCTIONS OF FOREST BY CHANGING NEEDLELEAF FOREST TO NEEDLELEAF-BROADLEAF MIXED FOREST

In this study, we examined the effects of the enhanced interception evaporation rate and surface roughness expected from changing needleleaf forest to needleleaf-broadleaf on flood mitigation functions. By conducting hydrological observations in the Hashimoto forestry area, which is a mixed forest of needle and broadleaf, the obtained interception evaporation rate and surface roughness were adapted to Nagayasuguchi dam and runoff simulation was conducted. We used a tank model for the spill simulation, which was evaluated in terms of peak flow rate and generation time. As a result, increasing the surface roughness reduced the peak flow rate by 6.1% relative to the 100 year Probabilistic rainfall, and increasing the interception evaporation rate reduced it by 3.6%. Therefore It was confirmed that this is an important function in flood reduction.