Author(s): J. J. Osullivan; W. R. C. Myers; J. F. Lyness; J. B. Cassells

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Keywords: Habitat; Environmental features; Hydraulic performance; Roughness coefficients

Abstract: A programme of habitat improvement of two rivers in Northern Ireland is described. Habitat condition was improved by re-introducing pool, spawning and nursery areas into river reaches where these fundamental habitat elements had become degraded by a combination of river drainage programmes and neglect. The integrity of these elements was sustained by incorporating groyne type structures to retain spawning gravels maintain pool depths. A field study was undertaken to assess the hydraulic performance of these environmentally acceptable channel in terms of the flood risks arising from the changes to the river. Results showed that the introduction of habitat features into rivers increases roughness. This increase is particularly prevalent at low flow depths but as discharges increase, features become drowned and roughness values tend towards pre-improvement scheme values. Consequently, the effect of these river changes is most pronounced at low depths where the channel can accommodate increases in water level, but for flood flows, their effect is minimal.

DOI:

Year: 2003