5.—(1) For the purposes of Part 1 of the Act—
“natural level”—
in relation to any part of surrounding land which would remain covered with residual water after an uncontrolled release of water from the structure, loch or other area (to which the land relates), means the level of the surface of the residual water; and
in relation to any other part of that surrounding land, means the level of the natural ground remaining after the construction, or any alteration, of the reservoir; and
“surrounding land”, in relation to a structure, loch or other area referred to in paragraph (a) or (b) of section 1(2) of the Act (“the reservoir”), means the land adjacent to the reservoir (including any land which would be adjacent to water held by the reservoir when the reservoir is holding the maximum volume of water that it is capable of holding).
(2) In the definition of “natural level” in paragraph (1), a reference to “residual water” is a reference to water which would not be capable of flowing out of the structure, loch or other area in question over natural ground in the event of an uncontrolled release of water from the reservoir.