Infiltration Number is another name for Drainage Texture; both are same, as the equations indicate. However, as a proof of this, you can refer the the report of Indo-British Ground Water Project (1984) on Ground Water Resources of the Upper Betwa River Basin, India published by Central Ground Water Board (CGWB), Govt. of India. Drainage density is an expression of the relative channel spacing in a fluvial dissected terrain (Mesa, 2006). It is also called Infiltration Number which depends upon a number of natural factors such as climate, rainfall, vegetation, rock and soil type, infiltration capacity, relief and stage of development of a basin (Smith, 1950). Soft or weak rocks uncovered by vegetation produce a fine texture, whereas massive and resistant rocks cause coarse texture. Sparse vegetation of arid climate causes finer textures than those developed on similar rocks in a humid climate (Dornkamp and King, 1971). The higher the Infiltration Number, lower will be the infiltration and higher runoff!