Soils that have been exposed to flood waters can be heavily polluted by inorganic and organic compounds. They are mainly compounds which appear in dissolved or suspended form flowing together with heavily laden floodwater, as well as compounds created as a result of reactions in the soil profile, mostly due to anaerobic transformation of organic matter. Heavy metals brought with flood waters are absorbed by the soil and also washed out from flood sediments by precipitation when the flood recedes. This paper presents the results of research on the effects of fertilization with ash from incineration or pyrolysis of biomass on the migration process of heavy metals (Zn, Cu, Cr, Ni, Pb, Cd, Mn) in the arable layer of soil. It has been shown that the metals in the flood sediment migrate actively in the soil profile what leads to the enrichment of the soils, also in the case of the soil fertilization with biomass ash.