Clogging of pore spaces of pervious rockfill detention dam during passage of suspended sediment laden flow through it, is one of the important issues which has been studied by some of researchers. Further study is still needed to achieve generable results to the real field condition. In this research we investigated semi empirically the initiation of sediment particle motion inside the pervious rockfill dam by conducting laboratory experiments alongwith dimensional analysis. A series of larger scale laboratory tests than previous studies has been conducted to collect experimental data. A dimensional analysis has been performed including all of effective hydraulic and physical parameters especially inertia of flow and rockfill characteristic...