Nothing in any of the provisions of this Part relating to any relevant works power shall authorise the appropriate agency to carry out any works at any place below the place to which the tide flows at mean high water springs, except in accordance with such plans and sections, and subject to such restrictions, as may, before the works are commenced, have been approved by the Secretary of State.
An approval for the purposes of subsection (1) above shall be given to the appropriate agency by the service on the appropriate agency of a notice containing the approval.
Section 38 of the Salmon and Freshwater Fisheries Act 1975 (tidal lands etc.) shall apply to any proposed construction, alteration or extension under section 156 above as it applies to any proposed construction, alteration or extension under that Act.
Section 74 of the Land Drainage Act 1991 (application to Crown and tidal lands), so far as it relates to lands below the high-water mark of ordinary spring tides shall apply, as it applies in relation to that Act, to the flood defence provisions of this Act.
In subsection (1) above the reference to a relevant works power is a reference to a power conferred by any of sections 159, 160, 162(2) and (3) and 163 above.