SMEC carried out a feasibility study for the development of the Nam Theun Two Hydroelectric Project on the Nam Theun River for the World Bank. The development included the construction of a downstream channel to convey releases from a regulating dam across the Gnommalat Plain to an enlarged section of the Nam Pit River on to the Xie Bang Fai River. The purpose of the study was to evaluate the flow patterns affected by the channel for a range of design floods, including the 10,000 year return period flood. SMEC’s services included: supervision of topographic survey for 70km of river cross sectioning, simulation of flood hydrographs for a wide variety of sub-catchments and flood return periods, development, calibration and application of a mathematical hydraulic flood model to simulate both the existing and future conditions, modification and adaption of the model to include the downstream channel and to simulate the changed conditions, interpretation of the results of the hydraulic model runs and preparation of flood plain maps.