Stormwater Group and CIWEM Wellington Regional Meeting

Water New Zealand Stormwater Group


Chartered Institute of Water and Environmental Management (CIWEM)

Water New Zealand’s Stormwater Group and CIWEM’s New Zealand Steering Group welcomes all members and non-members of both organisations to attend a joint Regional Meeting in Wellington. Drinks and nibbles sponsored by Wellington Water before and after the presentations. Share this invite with colleagues who have an interest in the water environment in the Wellington Region.

Venue: Wellington Water Ltd, Level 4, IBM House, 25 Victoria St, Petone
Date: Tuesday 19th March, Doors Open for drinks/nibbles at 5.00pm. Presentations start at 5.45pm.

RSVP online using the 'register' button to the right or by contacting


Dr Trevor Carey-Smith, NIWA

Trevor will give an overview of the recent update to NIWA’s High Intensity Rainfall Design System. While the basic methodology has changed little since version 3, there was a significant increase in the number and length of gauge records used. The methodology will be described, with difference between the new and old versions highlighted. In addition, considerable new research has been done quantifying the expected impact of climate change on extreme rainfall amounts. This has resulted in new guidance that suggests that the intensity of short duration events will increase much faster than previously thought.

Trevor is a climate scientist based in Wellington and has been with NIWA for over 10 years. He led the recent Envirolink funded update to HIRDS in conjunction with regional councils. He is a key researcher in the Irrigation Insight Endeavour Programme which is using co-innovative research to enable better environmental and economic irrigation decisions. He has been co-author on a number of climate change reports and guidance, most recently the 2018 MfE Climate Change Projections for New Zealand report. He currently leads NIWA’s Forecasting Weather project whose aim is to improve the accuracy of numerical weather prediction modelling in NZ.

Mussel Shells: Waste product or cheap and effective stormwater treatment

David Wilson, The Urban Engineers

David will discuss findings from the use of mussel shells as a filter media to treat runoff from the Waikawa Hardstand in Picton where boats are cleaned, sanded and repainted.The runoff has high levels of copper from anti-fouling paint, and zinc from sacrificial boat anodes, so it needs to be treated before it is discharged into the marina. The performance of the conventional sand/peat media in the original treatment system was suboptimal, and in 2017 Port Marlborough approved the change of filter media to mussel shells.Results to date indicate that the mussel shell media achieves similar levels of treatment to the original sand/peat filter but is more cost effective and has a higher flow rate so that the system is now treating more runoff.

David is a Principal Engineer and Director at The Urban Engineers where he has specialised in providing stormwater management advice.He has over 20 years’ experience in stormwater, water and wastewater engineering and has a particular interest in innovative solutions for stormwater treatment as well as Water Sensitive Design. David enjoys working with a variety of clients to improve both stormwater quality and stormwater quantity outcomes.

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