The waterfall method of SDLC is a series of stages which should be implemented for the creation of an information system. The stages must be in a particular order which should be reviewed at the end of each stage. The next stage can only be started when the previous stage has been reveiwed.
One advantage of this model is that each stage is completed and reveiwed before the next stage can be started. This ensures that the stage is perfected and there are no errors before continuing with the information system developement.
As well as this the model is simple and easy to understand and follow. The stages are clear and the user has a clear knowledge of how to follow each stage.
Due to the firmness of the model it is easy for the user to manage as each stage has specifiv deliverables and each stage has a reveiw at the end of the stage before the next stage can begin.
Overall the waterfall model is a very simple, strict model which has huge advantages for developers of smaller projects. The user knows what needs to be achieved at the end of each stage and can not continue on to the next stage until they have achieved this.
I hope this has given you a good idea of why there are advantages to using the waterfall model.