weir

The study found the highest levels of genetic isolation in rivers that were both polluted with metal and affected by physical barriers such as dams and weirs.

This showed how it is possible to maintain the full tidal range within existing dams or weirs.

The restoration of riverside forests, natural meanders in waterways and weirs in the mountains would all help diminish flooding, he said.

The city controls several weirs where water is diverted.

The weirs allow some fish to continue their journey upstream to spawn while yielding a harvest calibrated to the needs of the local community.