Author(s): Shaohua Marko Hsu; Chinkun Huang; Yanmin Chen
Linked Author(s): Shaohua Marko Hsu
Keywords: Porous cylinder; Levee protection; Bed scour/deposition; Angle of attack
Abstract: By observations in a series of laboratory experiments, porous cylinders were tested for levee protection in the downstream Da-jia River at Kch-Juang reach, Taiwan. The morphological situation of the river is braided with a steep slope and the bed material is mainly composed of gravel and cobbles. In the middle of a main stream and a considerable distance away from the protected levee on the river bank, four lines of porous cylinders were installed and arranged across a deep channel flowing towards the protected levee, which was reconstructed from a broken situation due to previous strong flow events. After the porous cylinders were initially installed in March of 2007, and before any major flood, the river-bed elevation around the installed porous cylinders was measured as a background reference. Since then, the EastAsian rainy season (plum rain) occurred in June, the Typhoon Sepat came in August, the Typhoon Wiptha came in September, and the Typhoon Krosa came in October, 2007. Elevation surveys between each strong-flow event indicate that the porous cylinders slowed down strong flow past them and caused deposition behind most cylinders which can reach 1.5to 2.0 m. Also, the major deep channel was divided into several paths, which detoured to different orientations from the original ones and mainly detoured along the line-up direction of the porous cylinders. As a result, levee protection was achieved due to this behind-cylinder deposition as well as the detour of the original deep channel which reduced the angle of attack onto the levee.