Proposed controls on shipping activity in the Marlborough Sounds: A review under s. 32 of the Resource Management Act

Croad, Richard, and Parnell, Kevin (2002) Proposed controls on shipping activity in the Marlborough Sounds: A review under s. 32 of the Resource Management Act. Technical Report. Opus International Consultants Ltd and Auckland UniServices Ltd, Wellington, New Zealand.

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The Marlborough District Council proposes to introduce a variation to the Marlborough Sounds Resource Management Plan to apply controls on shipping activity in the Sounds. This report provides an analysis of the proposed variation as required under section 32 of the Resource Management Act, 1991 (RMA). Section 32 sets out the steps and issues that must be considered when analysing provisions in policy statements and environmental plans, dealing with inter alia the extent to which regulation is needed, alternatives, benefits and costs, and whether the proposed regulation is necessary to achieve the purposes of the RMA, is effective and efficient. It is concluded in the report that: (a) The effects of ship waves are an environmental issue and should be considered under the provisions of the RMA. (b) The Second Schedule of the RMA contemplates that shipping is an activity that may be controlled under the provisions of an [Environmental Management] plan, and that it is appropriate for the Council to regulate such activity using the Marlborough Sounds Resource Management Plan. (c) There are various environmental effects of differing significance caused by ship waves in the Marlborough Sounds, and that such environmental effects are now widely recognised and managed at various sensitive sites around the world. Examples are presented and discussed in the report. (d) Different regulatory or legal approaches have been adopted around the world to manage environmental effects from ship waves. Detailed examples discussed in the report cover Denmark, Sweden, the United Kingdom and the USA. (e) Various options for management control of ship wave environmental effects are outlined in the report, but regulation is considered to be the most effective. It is also considered that ship speed is one of the most important parameters to control and is the easiest to monitor. It is concluded that setting a speed limit is the most efficient approach to control for both shipping operators as well as the Council subject to operators having the ability to seek an exemption to operate above the specified speed limits if they can demonstrate that the environmental effects will be acceptable. The report presents an analysis of the characteristics of ship waves and the dependency of these characteristics on various ship properties. It is demonstrated how the plan shape and period of the waves depends on the ship�s speed, and how the height of the waves is affected by the length, breadth, draft and speed of a ship and depth of the water. Under the proposed regulations, operators may apply for an exemption from the speed limits if they can demonstrate that, at a higher speed, the ship wave characteristics will comply with the Wash Rule, namely: Shipping Controls in the Marlborough Sounds Final Version 6.1 – 11 September 2002 4 T 4.5 0.5 H ≤ in which H is the wave height in metres, and T is the corresponding wave period in seconds, of the wave created by the vessel in 3 metres depth of water near the shoreline. This rule, as applied under the regulations, and its method of enforcement, is harmonised with the approach adopted in Navigation Bylaw 2000 that deals with safety issues in the Marlborough Sounds caused by High Speed Craft. The Wash Rule is the same (with improved definitions for H and T) as that adopted for similar purposes by the Danish and Swedish Maritime Authorities. The rule is based on assuming that the wave effects caused by conventional ships up to 2001 are generally acceptable and tolerated by the public. It is considered that it would probably be unacceptable and inefficient to base the rule on a much lower benchmark of natural wave effects in the Sounds. Analysis is presented in the report that demonstrates or explains: (a) How the Wash Rule has been derived and has been benchmarked against the wave effect of conventional ships that have operated in the Marlborough Sounds during the period 1982 � 2001 (noting that the benchmark excludes the Aratere). (b) Why the form of the Wash Rule is appropriate to manage ship wave environment effects such as wave breaking, wave run-up on beaches, beach face stability and long-shore transport. (c) How the Wash Rule compares with alternative forms of rules such as the �no harm� rule applied in the Rich Passage of Puget Sound, Washington, USA. (d) The details and accuracy of the method of transforming measured ship waves from the point of measurement to a standard depth of 3 metres, used for monitoring purposes. The basis of the 15 knot and 18 knots speed limits for permitted and controlled shipping activities respectively is studied in detail based on many measurements undertaken between 1982 and 2001. It is found that: (a) All conventional and High Speed Craft that currently operate, or have operated, in the Marlborough Sounds will comply with the Wash Rule for speeds up to 15 knots (the speed up to which ships are permitted to operate without constraint, i.e. is a permitted activity). (b) Most ships will comply with the Wash Rule for speeds up to 18 knots (the speed up to which ships may operate as a controlled activity, i.e. operate provided that they comply with the Wash Rule), including the currently operating High Speed Craft, the Lynx (Incat 057). However, the Aratere has measurably more severe wave effects than earlier conventional ferries operating in the Sounds and will sometimes exceed the Wash Rule at 18 knots. Shipping Controls in the Marlborough Sounds Final Version 6.1 – 11 September 2002 5 (c) Increasing levels of non-compliance with the Wash Rule is generally observed for larger ships and High Speed Craft for speeds above 18 knots (at which speed, ship operations are a discretionary activity requiring a resource consent under the proposed variation to the plan). The currently operating ships Aratere and Lynx (Incat 057) will probably not comply with the Wash Rule at speeds above 18 knots; there is no available data to assess if this will be the case for the Arahura. Finally, some recommendations and observations are made in the report dealing with (i) possible exemptions that may apply to allow ships to accelerate or decelerate through the so called critical velocity; (ii) mechanisms to allow the issue of temporary resource consents for ship field trials; (iii) possible statistical approaches to assessing compliance with the Wash Rule; (iv) some ideal but not essential refinements to the ship wave analysis methodology to allow for variations in local bathymetry; and (v) issues concerning real time versus stored location and speed data from ships used for compliance monitoring purposes.

Item ID: 1032
Item Type: Report (Technical Report)
Keywords: Marlborough Sounds, Shipping activity
Date Deposited: 03 Nov 2006
FoR Codes: 09 ENGINEERING > 0911 Maritime Engineering > 091104 Ship and Platform Hydrodynamics @ 0%
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