Wilson Inlet 6
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Managing the bar and the Inlet
Summary of Findings
- There are four key drivers of the water exchange and
sand movement in Wilson Inlet: rainfall and runoff in
the catchment, the wind conditions over the Inlet, and
the ocean wave conditions and the ocean sea level
conditions at the mouth of the Inlet.
- The natural variability in the system's drivers is high.
As a result the variations in marine exchange between
years can be more than four fold simply due to the
natural variation in the drivers.
- The marine exchange in any year is somewhat
dependent on the events that have occurred in previous
years. For example the build up of sand from a late
closing in May 1999 took two subsequent openings to
remove.
- In terms of management options at the bar we have
virtually no ability to influence the main drivers of the
water exchange and sand movement in Wilson Inlet.
Those factors that we can influence (the water level at
opening, dredging of the delta, the closure time) are of
secondary importance compared to the four main
drivers.
- Increasing marine exchange may remove more
nutrients but carries the risk of causing a release of
nutrients from the sediments greater than that removed
through the bar.
- Marine exchange can most effectively be improved by
removing the constrictions close to the mouth of the
Inlet rather than large scale dredging. Given the
variability in climactic conditions from year to year
the effects of any such dredging through the bar
should be observed over more than one year to gauge
the risks of sediment nutrient release in the Inlet.
- The review of the investigations, monitoring and
modelling conducted during the period 1994 to 2001
have shown that the hydrodynamic and coastal
processes of Wilson Inlet are both complex and
variable. Available knowledge on the risk and effects
of the various options is limited, hence there is some
uncertainty in the assessments.
- Managing the stratification risk is the most important imperative of any bar opening strategy.
