Modification of river hydraulics by the invasive diatom Didymosphenia geminata

Aaron I. Packman, Scott Larned, David Plew, Kay Vopel

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The diatom Didymosphenia geminata ("Didymo") forms thick and dense mats under low-nutrient and high-shear conditions. To investigate the effects of Didymo on open-channel hydraulics, we collected cobbles covered with Didymo mats from the Waitaki River, Canterbury, New Zealand. The cobbles were then emplaced in a recirculating flume and the system hydraulics were observed under several imposed flow rates. Following these measurements, the Didymo mats were removed from the cobbles, and the measurements were repeated over the bare cobbles. The mats overlapped and bridged gaps between cobbles, and thus were expected to reduce form drag. However, shear velocities and friction factors increased when Didymo mats were present, indicating that Didymo-covered beds are hydraulically rougher than the cobble beds despite the fact that the cobble surface is smoothed by the presence of the mats. We conclude that the mats introduce an additional roughness scale, and that their surface is much rougher than the bare stones. This conclusion is supported by direct visual observations of the mat morphology.

Original languageEnglish (US)
Title of host publicationWorld Environmental and Water Resources Congress 2008
Subtitle of host publicationAhupua'a - Proceedings of the World Environmental and Water Resources Congress 2008
DOIs
StatePublished - Dec 1 2008
EventWorld Environmental and Water Resources Congress 2008: Ahupua'a - Honolulu, HI, United States
Duration: May 12 2008May 16 2008

Publication series

NameWorld Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008
Volume316

Other

OtherWorld Environmental and Water Resources Congress 2008: Ahupua'a
Country/TerritoryUnited States
CityHonolulu, HI
Period5/12/085/16/08

Keywords

  • Hydraulics
  • Morphology
  • Rivers

ASJC Scopus subject areas

  • Management, Monitoring, Policy and Law
  • Water Science and Technology
  • Pollution

Fingerprint

Dive into the research topics of 'Modification of river hydraulics by the invasive diatom Didymosphenia geminata'. Together they form a unique fingerprint.

Cite this