3 1. INTRODUCTION 1.1. BACKGROUND OF THE MODARIA PROGRAMME The International Atomic Energy Agency (IAEA) organized a programme from 2012 to 2015 entitled MOdelling and Data for Radiological Impact Assessments (MODARIA), which had the general aim of improving capabilities in the field of environmental radiation dose assessment by means of acquisition of improved data for model testing, model testing and comparison, reaching consensus on modelling philosophies, approaches and parameter values, development of improved methods and exchange of information. The following topics were addressed in ten working groups: Remediation of Contaminated Areas ? Working Group 1: Remediation strategies and decision-aiding techniques ? Working Group 2: Exposures in contaminated urban environments and effect of remedial measures ? Working Group 3: Application of models for assessing radiological impacts arising from Naturally Occurring Radioactive Material (NORM) and radioactively contaminated legacy sites to support the management of remediation Uncertainties and Variability ? Working Group 4: Analysis of radioecological data in IAEA Technical Reports Series publications to identify key radionuclides and associated parameter values for human and wildlife exposure assessment ? Working Group 5: Uncertainty and variability analysis for assessments of radiological impacts arising from routine discharges of radionuclides ? Working Group 6: Common framework for addressing environmental change in long term safety assessments of radioactive waste disposal facilities ? Working Group 7: Harmonization and intercomparison of models for accidental tritium releases Exposures and Effects on Biota ? Working Group 8: Biota modelling: Further development of transfer and exposure models and application to scenarios ? Working Group 9: Models for assessing radiation effects on populations of wildlife species Marine Modelling ? Working Group 10: Modelling of marine dispersion and transfer of radionuclides accidentally released from land-based facilities The activities and results achieved by the Working Groups will be described in individual IAEA Technical Documents (IAEA-TECDOCs) where appropriate. This report describes the work of the Modelling of marine dispersion and transfer of radionuclides accidentally released from land-based facilities Working Group (Working Group 10).