 Before the continental collision occurred (which is defined as 50 Ma or before in Brookfield's model), longitudinal river system had dominated the Asian continent, where major river systems run parallel to the approaching regional thrust.Amidst the collision (which is referred as 20 Ma in Brookfield's model), the shape of river channels were affected by the approaching Indian continent.Although major river systems still flowed parallel to the thrust, they bent around both sides of the Indian continent since the collision exerted compressional force to the drainage basin.