Hydraulic Model Test on Advanced Diversion Strategies for the Erchong Floodway of the Tamsui River
Background
The Tamsui River Basin collects flows from the Dahan, Xindian, and Keelung Rivers, discharging floodwaters into the sea through the bottleneck section at Taipei Bridge. Due to the narrow channel at Taipei Bridge, along with riverbed erosion/aggradation dynamics and human intervention, the conveyance capacity of the Erchong Floodway has declined, increasing inundation risks during torrential rains. To enhance overall flood defense capabilities in Greater Taipei, the Planning Branch conducted the "Hydraulic Model Test on Advanced Diversion Strategies for the Erchong Floodway of the Tamsui River." Combined with numerical simulations, the study evaluates feasible solutions to boost the floodway's diversion capacity, providing a crucial basis for long-term improvement strategies.
Test Features
- Model Configuration: The test utilizes a fixed-bed distorted hydraulic model based on Froude scaling laws, with a horizontal scale of 1:300 and a vertical scale of 1:50. The model extends from the confluence at the entrance of the Erchong Floodway to the Tamsui River estuary, spanning approximately 75 meters in length and 35 meters in average width. It fully simulates flood diversion and water level fluctuations between the main Tamsui River and the Erchong Floodway.
- Scenario Evaluation: Hydraulic model validations were performed across various improvement strategies—including the current scenario, Phase 1 plan, compromise plan, Phase 2 plan, and subsequent plans (incorporating deep-channel excavation across the entire floodway section)—to evaluate diversion capacity, water level changes, and overall conveyance performance.
Application of Results
By cross-validating physical hydraulic modeling with numerical simulations, this project established the hydraulic characteristics and diversion benefits of various improvement schemes, delivering crucial technical evidence for long-term strategies regarding the Erchong Floodway.
The results offer planning references for capacity improvements at the Taipei Bridge bottleneck section. They assist in enhancing the diversion capacity of the Erchong Floodway, lowering peak water levels and flood risks in the mainstream channel, and supporting future planning, design, and governance schemes for major flood control initiatives in Greater Taipei—ultimately reinforcing climate change adaptation and regional flood resilience.