The study applied one dimensional numerical model to evaluate the variation of hydraulic and sediment regulating capacity when large scale sediment event occurred. In order to improve the accuracy of numerical model for simulation sediment regulating capacity in river notch, the numerical model modified the pressure force term of momentum equation respond to the river width variation. The numerical model was tested the stability, water and sediment volume conservation analysis to demonstrate the stability and precision of numerical model. Laboratory investigation was carried out to validate the hydraulics and sediment deposition variation. The simulation results were comparable to laboratory experiments. The numerical simulation considered contraction ratio, contraction length, contraction inlet angle, and upstream sediment supply rate to understand sediment regulating capacity. The result of numerical tests showed that numerical model has the ability to simulate the hydraulics and sediment deposition dynamic response of river width variation affected by river notch.