Abstract: Along with the development of Nanjing city, the regulation project of Xinjizhou reach, which is located in the upstream of Nanjing, is under implementation. But the regulation program has been controversial over the last decade because this branch of the Yangtze River is changeable. The focus of controversy mainly lies in the effect of blocking the middle branch on the river’s stability. Since hydrogeometric relation is an important parameter reflecting the stability of river reach, we analysed the hydrogeometric relation before and after the implementation of the regulation project based on the result of 2D mathematical water-sediment model research. Result suggests that if the regulation program of blocking the middle branch is adopted, the left branch of Xijizhou reach is prone to deposition, but no big influence is shown for the right branch.

Key words: Xinjizhou reach of the Yangtze river, river regulation, hydrogeometric relation, stability of river reach, mathematical water-sediment model