Laboratory experiments have been carried out to study the characteristics of sediment transport in steep streams. The question is discussed wether an armoured surfaces is destroyed due to the transport of material, because additional impulses are acting on it, or the layer is sheltered by the transported material, because a part of the stream power is used to move the material. According to the results of the presented experiments, in which the influence of the feeding rate and the feeding duration have been investigated, transported material reaching an armoured river section from upstream always remobilzes bed material, which is immobile under clear water flow conditions. To decide if a static armour layer is either destroyed or not, two simple criteria were chosen: one considering the grain-size distribution of the eroded bed material, and another, which referes to the amount of eroded bed material. Laboratory experiments have been carried out to study the characteristics of sediment transport in steep streams. The question is discussed wether an armored surfaces is destroyed due to the transport of material, because additional impulses are acting on it, or the layer is sheltered by the transported material, because a part of the stream power is used to move the material. According to the results of the presented experiments, in which the influence of the feeding rate and the feeding duration have been investigated, transporting material reached an armored river section from upstream always remobilzes bed material, which is immobile under clear water flow conditions. either decide on a grain of size distribution of the eroded bed material, and another, which referes to the amount of eroded bed material.