An effectiveness evaluation method for debris flow control engineering for cascading hydropower stations along the Jinsha River, China

Four large hydropower stations are located along the Jinsha River, in an area that has the highest frequency of large damaging debris flows in China. The total power generation capacity of the dams is > 42 million kilowatts. Through field investigation, laboratory analysis, model calculation, and statistical analysis, we studied the debris flows occurring in the gullies near the Baihetan hydropower station to determine the characteristics of their dynamic parameters and the effectiveness of existing debris flow control measures. The dynamic parameters of debris flows vary significantly because of the different characteristics of the fluvial basins and their longitudinal slope gradients. Evaluation results showed that the existing debris flow control measures in the Aizi and Dazhai gullies should be able to withstand events with 100-year recurrence period. The debris flow risk in these gullies is therefore low in the present situation. It is important to note that these control measures would also be adequate for events with 500-year recurrence period; therefore, the debris flow risk would remain low in the theoretical future situations. We propose an evaluation method of the effectiveness of debris flow engineering control based on an analysis of the engineering measurements' effectiveness. The research results can be implemented to improve the design of the Baihetan hydropower station. More importantly, the results can be applied for the development of evaluation methods of the effectiveness of other similar and significant projects in China and elsewhere.