It is worth remembering that lows flows and shallow water are challenges to migrating fish.
The video below represents remediation to an upgraded urban storm water pipe serving a small tributary of the Maitai River near Nelson, NZ.
The upgrade involved upsizing the pipe and removing the perch at the outlet.
– Base flows of the tributary are approximately 1L/S
– Pipe length 300M
– Pipe gradients range from 2%-12%
You will see an increase in the depth and width of the water along with bed-material beginning to accumulate.