What

Width to depth ratio of bankfull width. The ratio of bankfull channel width (the width at the top of the bank determined by its extent when full of water, usually once in two years), is optimal for fish and aquatic insect habitat if less than 7:1 (Rosgen 1994). A very wide and shallow stream with a width/depth ratio of more than 25:1 is considered poor habitat for fish and the macroinvertebrate food supply they depend on (Gibson 1994; Ball 1982). A tape measure and meter stick are used to measure the width and depth of the channel.