Chapter 9 - Coastal Marine mouths to lessen potential effects of flooding events. The ability for people or authorities to undertake this activity provides considerable benefits and it is likely that the need for this activity will continue in the future. Therefore, the Plan needs to provide for alterations to the foreshore and seabed where there are no or only very minor adverse effects resulting. The main issue in relation to alteration is the need to provide for alterations to the foreshore and seabed while avoiding, remedying or mitigating the adverse effects of this activity. The objective and policies which follow address this issue, while the following examples of foreshore and seabed alterations seeks to further explain and define the issue. These examples are not exhaustive and the provisions of this section apply to any alteration to the foreshore or seabed within the coastal marine area. Alterations, that change the physical shape of the foreshore and/or seabed include: Reclamation, Drainage and Impoundment Outside the main port areas at Picton and Havelock, large scale reclamations are not a feature of the Sounds. Aside from the reclamations associated with the commercial facilities at Elaine Bay and Oyster Bay (Port Underwood), reclamations in the Sounds are generally limited to small abutments for jetties. These are commonly two or three square metres in area. The impoundment which bounds Waikawa marina is effectively a reclamation of the foreshore and seabed. Probably the most significant adverse effect of a reclamation is the burial of the seabed. This threatens habitats associated with the seabed and potentially the life-supporting capacity of a much larger surrounding area. Other potential effects associated with reclamation include interruption to the water movement patterns, exclusion of water-based uses, visual impacts and construction effects. Dredging Dredging of the foreshore and seabed is generally undertaken to allow ship or boat navigation in areas which would otherwise be too shallow. It is most often required around ports and marinas, particularly within and approaching the Havelock port area. Dredging is also carried out for the purpose of clearing, cutting or realigning river mouths. Generally though, very little dredging and spoil disposal occurs in the Marlborough Sounds. Periodically, a limited amount of material needs to be removed from alongside jetties. This normally occurs at the head of a bay where siltation has occurred over a number of years and has eventually made a jetty unusable at low tides. There are various means of disposing of dredging spoil, but generally within the Sounds, land disposal has been used and preferred in the past. Both dredging and dredging spoil disposal can have significant adverse environmental effects. The main effect of dredging is the physical destruction and/or removal of any benthic aquatic life within the dredged area (organisms that live in or on the bottom sediments). Dredging can also affect water movement patterns and alter the physical nature of sediments, thus potentially affecting habitats. 9 - 15