Fluvial processes and their impact on the finless porpoise’s habitat after the Three Gorges Project became operational

Since the filling of the reservoir of the Three Gorges Project(TGP)dam in the Yangtze River in 2003,erosion downstream from the dam site has affected the finless porpoise’s habitat.In this study,a one-dimensional(1D)fluvial process mathematical model is used to calculate flow and sediment transport in the middle and lower reaches of the Yangtze River,including the finless porpoise’s habitat.By analyzing the calculation results for the water resources,suspended load,and bed materials in the finless porpoise’s habitat after the riverbed deformation,we evaluated the possible impact on this rare Yangtze River aquatic animal.The results show that,with the erosion of riverbed over the next 20 years,the water quantity comprising the habitat will decrease to half of its present amount,and the bed materials will be eroded to coarse grading,such that the reserve will become a gradually disappearing stream.Effective engineering measures should be used to decrease the erosion in the main channel,in case the overall erosion cannot be stemmed and controlled,to ensure an adequate water volume flows into the finless porpoise’s habitat.