Subject to the following provisions of this section, in this Act, except where the context otherwise requires, "development," means the carrying out of building, engineering, mining or other operations in, on, over or under land, or the making of any material change in the use of any buildings or other land.
For the purposes of this Act " building operations " includes—
The following operations or uses of land shall not be taken for the purposes of this Act to involve development of the land—
and are not works for making good war damage or works begun after 5th December 1968 for the alteration of a building by providing additional space in it underground;
The Secretary of State may in a development order specify any circumstances or description of circumstances in which subsection (2) does not apply to operations mentioned in paragraph (a) of that subsection which have the effect of increasing the gross floor space of the building by such amount or percentage amount as is so specified.
The development order may make different provision for different purposes.
For the avoidance of doubt it is hereby declared that for the purposes of this section—
For the purposes of this Act mining operations include—
Where the placing or assembly of any tank in any part of any inland waters for the purpose of fish farming there would not, apart from this subsection, involve development of the land below, this Act shall have effect as if the tank resulted from carrying out engineering operations over that land; and in this subsection—
" fish farming " means the breeding, rearing or keeping of fish or shellfish (which includes any kind of crustacean and mollusc);
" inland waters " means waters which do not form part of the sea or of any creek, bay or estuary or of any river as far as the tide flows; and
" tank " includes any cage and any other structure for use in fish farming.
Without prejudice to any regulations made under the provisions of this Act relating to the control of advertisements, the use for the display of advertisements of any external part of a building which is not normally used for that purpose shall be treated for the purposes of this section as involving a material change in the use of that part of the building.
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