10:07 AM - 10:30 AM
[AHW26-05] Water dynamics governed by surface-subsurface exchanging flow in Kanogawa River Basin
★Invited Papers
Keywords:Kanogawa River Spillway, Hyporheic Zone, Surface and Subsurface water exchange flux, Ecosystem, Simulation
We developed an integrated watershed model to deepen and extend investigations how ecosystems respond to changes in river flow conditions in the Kanogawa River watershed (Shizuoka Prefecture, Japan). In 1965, an artificial flood discharge channel was constructed at 17.8 km from the river mouth, diverting floodwater into Eura Bay and serving as a flood mitigation structure for the downstream urban area. To examine the changes in flow conditions during flood events caused by the operation of the Kanogawa River floodway, the estimated ecological response, and the differences between normal and flood conditions, we conducted a three-dimensional integrated watershed modeling focusing on Hyporheic Exchange Flux (HEF).
For this study, we constructed two models with different spatial regions and resolutions. The first model, the river channel-scale model, provides a detailed representation of the area around the Kanogawa River floodway. This model was used to analyze changes in flow conditions during floods with and without the floodway, and to evaluate the spatiotemporal distribution of HEF. Additionally, we examined the distribution of Pleioblastus simonii (Medake) groves in riparian vegetation and analyzed their correlation with river flow conditions, particularly in meandering sections.
The second model, the watershed-scale model, covers the entire Kanogawa River watershed from its headwaters to the river mouth and visualizes the hydrological structure of the entire catchment. Using HEF estimations obtained from the river channel-scale model, we developed an upscaling method to extend these findings to the entire watershed. This upscaling method addresses challenges for large-scale models, such as the tendency to overestimate the difference between river water levels and groundwater levels in the hyporheic zone.
The watershed-scale model developed in this study quantifies and visualizes the water balance under both normal and extreme rainfall conditions. Additionally, it provides insights into the hydrological behavior of various landscape components, including river channels, rice paddies, forests, and geological formations, particularly in response to floodwater volume changes during extreme rainfall events. This model significantly enhances our understanding on the specific water dynamics of the Kanogawa River Basin in the context of increasing extreme weather events.
This study was supported by the River Works Technology Research and Development Program from the Ministry of Land, Infrastructure, Transport and Tourism, Japan.
For this study, we constructed two models with different spatial regions and resolutions. The first model, the river channel-scale model, provides a detailed representation of the area around the Kanogawa River floodway. This model was used to analyze changes in flow conditions during floods with and without the floodway, and to evaluate the spatiotemporal distribution of HEF. Additionally, we examined the distribution of Pleioblastus simonii (Medake) groves in riparian vegetation and analyzed their correlation with river flow conditions, particularly in meandering sections.
The second model, the watershed-scale model, covers the entire Kanogawa River watershed from its headwaters to the river mouth and visualizes the hydrological structure of the entire catchment. Using HEF estimations obtained from the river channel-scale model, we developed an upscaling method to extend these findings to the entire watershed. This upscaling method addresses challenges for large-scale models, such as the tendency to overestimate the difference between river water levels and groundwater levels in the hyporheic zone.
The watershed-scale model developed in this study quantifies and visualizes the water balance under both normal and extreme rainfall conditions. Additionally, it provides insights into the hydrological behavior of various landscape components, including river channels, rice paddies, forests, and geological formations, particularly in response to floodwater volume changes during extreme rainfall events. This model significantly enhances our understanding on the specific water dynamics of the Kanogawa River Basin in the context of increasing extreme weather events.
This study was supported by the River Works Technology Research and Development Program from the Ministry of Land, Infrastructure, Transport and Tourism, Japan.