There have been situations where road developers were able to protect watercourses with consultation and advance planning, according to Ms Gretta Hannigan, senior environmental officer with the Eastern Regional Fisheries Board (ERFB).
She cites the Dundrum river as one example, where the developer involved agreed to improve other parts of it. The river, which rises at Three Rock Mountain and flows northwards by Ballinteer, Sandyford Road and Dundrum village west, includes a millrace and pond which powered two mills at Packhorse bridge, upstream of Milltown bridge, on the Dodder.
"You are talking about a part of industrial history which could so easily be lost," she says.
The construction of houses at Cherrywood, Loughlinstown, Co Dublin, and realignment of the N11 Bray road is another example.
To accommodate the construction of a new access bridge and road network, a new river channel was created and the Shanganagh river was diverted into it during 1998.
This involved removal of fish by ERFB staff, and closure of the original river channel, with fish being returned to the new system.
By spring of 1999, the fish stock was assessed and the new channel was re-established as a significant brown trout nursery.
Another example was the use of a "fish-friendly" culvert in a road-improvement design by a private developer at Druid's Glen, in south Dublin.
Stone pitching was embedded in the 30-metre-long culvert base, to mimic the natural river bed, and light shafts were introduced every three inches.
The work was completed during the summer, outside a critical fish-spawning period.
