The chemical speciation model BIOCHEM was extended with ecotoxicological transfer functions for uptake of metals (As, Cd, Cu, Ni, Pb, and Zn) by plants and soil invertebrates. It was coupled to the object-oriented framework ORCHESTRA to achieve a flexible and dynamic decision support system (DSS) to analyse natural or anthropogenic changes that occur in river systems. The DSS uses the chemical characteristics of soils and sediments as input, and calculates speciation and subsequent uptake by biota at various scenarios. Biotic transfer functions were field-validated, and actual hydrological conditions were derived from long-term monitoring data. The DSS was tested for several scenarios that occur in the Meuse catchment areas, such as flooding and sedimentation of riverine sediments on flood plains. Risks are expressed in terms of changes in chemical mobility, and uptake by flood plain key species (flora and fauna).