Covered streams see the light of day

Posted on July 25, 2012

In urbanised environments, streams are often channelled below streets, buildings and open spaces.  The proportion of running water contained in culverts can be high – for example, in Switzerland it’s around 20% and in Denmark 15%.  Environmental problems associated with culverts include their tendency to modify flow patterns and habitats, impede fish passage, reduce light levels and plant growth, and isolate the stream from the surrounding terrestrial environment.  In many cases there are opportunities for achieving environmental, social or economic benefits by opening up culverted stretches of stream (“daylighting”) to restore more natural conditions.  Daylighting can increase  ecological integrity, reduce the risks of channel blockage and flooding, lower the costs of management and maintenance, and improve recreational and aesthetic values.  Because our current understanding of the effects of daylighting is based mainly on anecdotal evidence, an online database has been set up (at, so that researchers and practitioners can share case study information.

Reference:  Wild, T.C., Bernet, J.F., Westling, E.L. & Lerner, D.N.  2011.  Deculverting: reviewing the evidence on the ‘daylighting’ and restoration of culverted rivers.  Water and Environment Journal 25, 412–421.