Experimental Study on Scour and Protection of Riverbank levee foundation
Taiwan's rivers are heavily impacted by steep topography and typhoon floods, resulting in complex flow regimes. In certain river reaches, oblique flow impacts cause severe scour at the levee foundation, potentially leading to embankment collapse or structural failure. Due to a historical lack of systematic test data regarding foundation scour under oblique flow conditions, uncertainties remain in engineering design and flood resistance evaluations after repairs.
To clarify the mechanisms of levee foundation scour and establish design criteria for protective works and design criteria for protective works, this research spanned 9 years (2012–2020) across three phases under the project "Experimental Study on Scour and Protection of Riverbank levee foundation." Through hydraulic model testing, it investigated the impact of oblique flows on foundation scour to provide technical reference data for engineering design.
Technical Features
This study utilized scaled hydraulic models based on Froude similarity law, constructing testing models at 1/50 and 1/100 scales to simulate levee foundation scour behaviors under various river flow conditions.
Tests evaluated different oblique flow attack angles (30°, 60°, and 75°). Through multiple sets of clear-water tests, the effects of discharge, bed sediment grain size, bed slope, unsteady peak discharge, and flood hydrographs on scour depth were systematically analyzed.
During the study period, a total of 339 test runs were completed, covering fixed-bed tests, movable-bed tests, protection work tests, and unsteady flow tests. The research thoroughly explored hydraulic flow field characteristics, general scour, and maximum footing scour development mechanisms under oblique flow, while assessing the protective performance of various armor configurations.
Applications & Results
By performing regression analysis on model test results and field observation data, empirical formulas for embankment footing scour under oblique flows were established, providing quantitative evaluation metrics for river management and embankment design.
Testing demonstrated that installing footing protection (such as specially shaped armor blocks) effectively reduces maximum scour depth by an average of approximately 46%, significantly enhancing the structural safety of embankments.
These findings can be directly applied to the planning, design, scour risk assessment, and maintenance management of new and rehabilitated river embankments. They offer essential technical reference for River Management Branches conducting flood control projects, strengthening the resilience of river flood protection infrastructure against extreme flood events.