Channel morphology with permeable spur dykes under downward seepage

Seepage around river structures increases the risk of sediment removal and deeper scour, potentially compromising the stability of structures such as spur dykes. These spur dykes are installed along riverbanks to redirect water flow, control erosion and stabilise riverbeds. This study aimed to investigate the effects of three different combinations of permeable and impermeable spur dykes on bed morphology and scour progression around T-shaped spur dykes with seepage and no seepage conditions. Set A comprises three impermeable spur dykes in series, while set B (60%, 0%, 0%) and set C (60%, 30%, 0%) feature combinations of permeable and impermeable spur dykes with different percentages allocated to each spur. The results revealed significant reductions in the maximum scour depth at the initial spur dyke under conditions without seepage when permeable sets B and C were used; the values were 37.6% and 55.2%, respectively, lower than those for impermeable set A. When considering V_S1, applying permeability set B leads to a reduction of 38.5%, and using permeability set C results in a reduction of 42.4% compared to impermeable spur dykes (set A). The findings indicated that the most effective combination for determining spur dyke permeability was set C, while the most substantial scour depth was produced in spur dyke set A.