1. PART I: brief review report, including research gaps & possibilities
PART II: key figures & tables
PART III: annotated bibliography
Resources reviewed:
~140 journal papers, theses, published & unpublished reports from Lyttelton Port Company, ECAN, NIWA, Cawthron Institute; maps, aerial photographs; hydrographic charts; structure plans.
People consulted: ECan, LPC, Rapaki, NIWA, UC, harbour residents, BP Zone committee
Monday 28th July 2014 Rapaki Hui Keynote

2. Harbour seabed accretion requires:
sediment
inputs
hydrodynamic conditions that allow settling & net accumulation +
ECAN photo

3. State of knowledge on sedimentation & circulation
Numerous studies examined sedimentation &/or circulation - predominantly assessing upper harbour mudflat growth OR port operation effects in the central & outer harbour.
The harbour inlet is naturally prone to infilling over geological time, but infill rates have been accelerated by human activities in the catchment & harbour.
Patterns of sedimentation in the upper harbour over the past century have been dominated by accretion in response to catchment sediment inputs &, very likely, port activities, while sedimentation in the central to lower harbour has been variable & responsive to port dredging & spoil dumping.

4. e.g. Head of the Bay core accumulation rates (Goff 2005)

5. State of knowledge on sedimentation & circulation
Main sediment sources for each sub-catchment = known (ECan 2008 report) even if exact rates debated (Shearer 2010). Using existing info, there is significant scope to reduce sediment inputs (Bolton-Ritchie 2011) to influence harbour sedimentation .
Understanding the effects of present-day port activities on harbour sedimentation & circulation has advanced a lot since Questions remain regards the effects of historical changes in port structures & bathymetry.

6. e.g. Recent harbour field & model studies

7. State of knowledge on sedimentation & circulation
Within existing research, few studies consider the harbour as a whole system. Catchment or harbour activity effects on the inlet sediment budget cannot be fully assessed via such compartmentalised approaches.
Investigation techniques used in one area are not equivalent to those used elsewhere, making comparisons of sedimentation patterns & trends difficult.
Some suggestion that harbour operates as a series of sedimentation ‘cells’????

8. Future research possibilities
Techniques applied to one area could be applied to remaining areas to improve whole-harbour comparisons of the causes & rates of sedimentation (e.g. coring), as would ongoing scientific monitoring effort throughout the whole harbour.
Compilation & comparison of all existing data on depths for whole harbour over time: analyse in relation to existing studies to better understand the harbour sediment system & key sedimentation influences over time.
No up-to-date sediment texture map of complete harbour seabed - GIS compilation of all existing sediment texture data would be a start.
Compare core results to major historical land-use & port structure changes.
New studies: Model hydrodynamics & mudflats to improve understanding of the harbour’s physical systems & appreciate effects of different human activities.
Apply new sediment techniques in whole harbour investigations (e.g. Swales et al. 2011; McLaren 2012).
Suspended sediment field investigation: measure SSC & potential causes in close spatial proximity for several sites around the harbour.

9. Last but not least
Most of the suggested future research requires a whole-harbour perspective &, probably, a greater level of harbour stakeholder collaboration/ shared interest.
Following the main recommendations of existing reports on how to reduce external inputs of sediment into Lyttelton could have measurable, positive outcomes for sedimentation rates: Q effects on biota?
Past structures may have influenced sedimentation patterns in parts of Lyttelton Harbour via hydrodynamic changes: Q effects on biota? – Q effects of future structures??

10. Whakaraupō Lyttelton Harbour
Google Earth satellite mosaic, 15 Feb 2011