Six physical models of gabion stepped weirs were used to study the hydraulic of flow through and over gabion stepped weirs. The models have three downstream slopes 1:1, 1:2, and 1:3 (V:H) filled with two types of rockfill materials (Table 1). All models were designed to a scale of 1:10 with four steps and had the same height, width, step height, and broad crest (height 400 mm, width 500 mm, step height 100 mm, and broad crest 200 mm) (Figure 2). The rockfill materials were crushed stone of nominal size (37.5–13.2 mm) D₅₀ = 23 mm and rounded gravel of nominal size (26.5–13.2 mm) D₅₀ = 16 mm. The average porosity was 0.42 and 0.38, respectively, which was measured three times by direct method. The gabion baskets were made of 1.5 mm galvanised wire mesh with square openings of 12.7 × 12.7 mm.