Presentation on the complexities of Muri Lagoon hydrodynamics

Last week Principal Coastal Engineer Matt Blacka spent a few hours with stakeholders from various government agencies and NGOs, working through the finer details of the hydrodynamics of Muri Lagoon.

Based on WRLs comprehensive field investigation and monitoring of the lagoon undertaken last year; the technical presentation stepped through the complexities of the system, discussing key drivers of the hydrodynamics and flushing of the lagoon, as well as the influence of climatic conditions on lagoon processes.

Muri has an intricate fringing reef and lagoon system, where wave setup on the outer reef creates gradients in water level through the lagoon, driving lagoon flows and flushing. As well as the influence of wave energy, the currents in the system are also modulated by tides and the submergence of the outer fringing reef, with wave direction also having a significant impact on the way currents flow through the lagoon. 

Muri Lagoon, one of the main tourism areas of the Cook Islands, has been a significant concern in recent years due to periods of excessive algal growth and degraded reef health. WRLs work on the environmental investigations for the Mei te vai ki te vai project helped to properly understand the system and confirm the causes of the problems. Matt’s presentation was a great opportunity for participants to gain a more detailed understanding of the system, and to understand the role of lagoon hydrodynamics on water quality and flushing.