28. 5. 97

PROJECTS AND PROPERTY COMMITTEE

9 MAY 1997

A special meeting of the Projects and Property Committee

was held on Friday 9 May 1997 at 10.00 am

PRESENT: Councillor Ron Wright (Chairman),

The Mayor,

Councillors Oscar Alpers, Ishwar Ganda,

Ian Howell and Denis O'Rourke.

APOLOGIES: An apology for absence was received and accepted from Councillor Gail Sheriff.

An apology for lateness was received from Councillor Oscar Alpers who arrived at 10.07 am following the exclusion of the public, and who was present for clause 3 only.

ABSENT: Councillors Carole Anderton, Morgan Fahey,

and Alister James.

The Committee reports that:

PART A - MATTERS REQUIRING A COUNCIL DECISION

1. CHRISTCHURCH PIER - STAGE 1

REPORT ON WATER DEPTH AT THE SEA END RR 5032

Officer responsible	Author
Property Projects Manager, Gilbert van Schaijik	David Clark, Engineer Structural
Corporate Plan Output: Corporate Plan, Volume 2, Capital Output, page 8.4.55

The purpose of this report is to cover the issue of extension of the pier in response to a request from a member of the public.

The matter of the water depth at the sea end of the pier and a suggestion that increasing the pier length by say two bays (40.0 m) would improve depth for boat launching and fishing has been raised as a personal comment by Mr Mike Stevens ex-Councillor and Trustee of the Pier Promotion Trust.

The pier has not been specifically designed for either fishing or boat access but we have, however responded to these comments by carrying out a further survey of the seabed profile at the pier to allow comparison with previous surveys made on 24 September 1992 and 31 January 1996 and passed the results on to Mr Gary Teear of OCEL Consultants, our adviser on the marine aspects of the pier design.

Mr Teear comments as follows:

"The three beach profiles taken at the pier location on 24 September 1992, 31 January 1996 and 17 April 1997 exhibit the normal variability expected for a sand beach profile over time.

All sand beaches constantly undergo a sequence of longshore and onshore/offshore exchanges of sand as they attempt to adjust in form and volume to variations in incident wave conditions, tides, winds and currents. Storm waves cause erosional episodes resulting in loss of sand from the upper beach, lowering and flattening the foreshore. The sand taken offshore forms one or more bars separated by channels. In the period between storms swell waves break down the bar system and move sand ashore. The profile at any one time then is a snapshot reflecting the time since the last erosional episode.

The depth at the end of the pier will vary over time as a consequence of this onshore/offshore exchange of sand. If a bar forms at the end of the pier after an erosional episode or storm, as has happened at the present time - a common event in fact - it is likely that there will be a relatively deep channel inside it. The bar will also be relatively flat and broad crested, a fact not reflected in the vertically exaggerated scale used for the profiles. Because of the relatively flat nature of the crest there are unlikely to be dramatic depth changes within a few metres. Extending the pier two more bays will not produce a significant change in water depth at the end - as is evident from the profiles. To achieve that, the pier would have to be extended another 100 metres. Even in that case the depth would not be that much greater if the beach had the profile as at 31 January 1996 where swell waves have obliterated the bar system except for a small channel well inshore."

Recommendation: That the report be received and that no further action be taken.

PART C - REPORT ON DELEGATED DECISIONS

TAKEN BY THE COMMITTEE

2. RESOLUTION TO EXCLUDE THE PUBLIC

The Committee resolved that the draft resolution to exclude the public set out on page 4 of the agenda be adopted.

CONSIDERED THIS 28TH DAY OF MAY 1997

MAYOR

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