Abstract: Roughening in river models is a very important method to meet resistance similarity. A flume experimental study is conducted for the hydraulic resistance of roughening elements shaped as letter “Y”. The results show that this kind of roughening elements can possess a wide range of roughness, and the hydraulic resistance decreases with the increase of space between roughness elements, but reduces slowly to a constant, and that flow enters into the turbulently rough zone when Reynolds number reaches about 3 500, in which the hydraulic resistance decreases with increase of relative submergence degree, reducing slowly to a constant too.