How far can you push a HEC-RAS model and other conundrums – a Nam Theun 2 case study

Designed by 2007, built by 2010, limits pushed by 2011; the occurrence of an extreme flood event at the Nam Theun 2 hydropower dam system in Laos sparked a reassessment of the hydrology resulting in a 30% increase in design flows and leaving the flood release infrastructure well short of the required capacity. This increase and subsequent attempts to re-analyse the release structures, ranging from simplified HEC-RAS modelling to sophisticated CFD and physical modelling, serve as examples of the uncertainty and risks that can be encountered in the design of hydraulic structures