Answer:
Series of topographic maps in chronological order.
Step-by-step explanation:
If we see the map in a chronological order, then that gives us the rough idea about the flow, angle and area of the river. A detailed study of the topographic map gives us the idea about the direction in which the river has flown over the years. Based on this map we can successfully form a model which will give us a future position and flow pattern of the river. So in the light of the above facts the use of the topographical maps in the chronological order is the most appropriate tool for mapping the future course of the river.