111 / 2025-04-24 12:56:08

Porous Material for Riverbank Protection in Braided Rivers with significant change of Discharge

Porous cylinder, Levee protection, Bed scour/deposition, Angle of attack.

After observation in series laboratory experiments, Porous Cylinders were tested for levee protection in the downstream Da-jia River at Kch-Juang reach, Taiwan. Morphological situation of the river is braided with steep slope and the bed material is mainly composed of gravel and cobble. In the middle of a main stream and with considerable distance away from the protected levee on 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 East-Asian 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 1.5 to 2.0 m. Also, the major deep channel was divided into several paths, which detoured to different orientation from the original ones and mainly detoured along the line-up direction of the porous cylinders. As a result, levee protection achieved due to this behind-cylinder deposition as well as detour of original deep channel which reduced the angle of attack onto the levee.