Floods occurring as a consequence of very heavy rainfall in the southeastern part of Germany resulted in the erosion of waste dumps and tailings along the Mulde river system. Components derived from these sources, e.g., slags and charcoal, can clearly be recognized downstream in the flood sediments. As a consequence, the flood sediments contain in part extreme concentrations of heavy metals (up to 14,000 ppm Pb), As (up to 8,000 ppm), and U (up to 47 ppm) in the clay fraction. However, due to the origin of the contaminants, coarser grain fractions likewise contain extreme, though generally lower, concentrations of toxic elements. Initial leaching experiments show, that the toxic elements are readily leached from both, the clay fraction and from coarser fraction. Hence flood sediments contaminated by material derived from waste dumps and tailings constitute a considerable risk for land use.