Floods are among the most persistent natural disasters that lead to massive economic and human loss globally. In this regard, this study has proposed an optimisation model for evacuating people before the occurrence of the flood using bus transit. The process of evacuation commences with the issue of warning and extends up to a certain time before the flood forecasts to strike. This model provides an optimised framework for 1) Locating pickup points and shelters, 2) Assigning pickup points to the nearest shelter by opting the shortest route among the available routes. On the basis of demand, each pickup point is allocated with a certain number of trips. The modelling of dispatch sequence of public buses, random adventing of evacuees at pickup points and evacuees transit to the shelters are presented by developing a simulation tool. The results of simulation serve for assessing the route design and then, a local search heuristic is suggested to improve the route design during the evacuation.