... the stones on a bed and how to assess the stability of the stones are central and most challenging in stone stability research Firstly, it is important that the hydraulic forces exerted on the stones ... for the assessment of stone stability: i) the stability threshold concept and ii) the stone transport concept Together they form four mechanical model concepts for stone stability, as shown in ... University of Technology Keywords: Stone stability, stone transport, stone entrainment, incipient motion, threshold condition, bed protection, bed damage, non-uniform ow, turbulent ow, decelerating...