The Geography of the Puranas c11.s2.13

c11.s2.13

(2) Major, wide and deep rivers with extensive flood plains separate human groups. Here population groups occupy their high banks, settle as near the river as practicable but avoid its floodplain altogether. The river serves as a boundary line between the groups on its both sides and each population group and subsequently each janapada is limited to and defined by the ‘doab’ of two such adjoining rivers.