83.— No claim lies against the Minister or IFI for flooding or other consequential damage due to the continued existence of any structure (including a fishing weir or a fishing mill dam which, on the date of vesting in or acquisition by the Minister or IFI of a fishery, formed part of or existed in such fishery) unless the Minister or IFI, as may be appropriate, shall have increased the height of such structure or shall have closed any openings or gaps therein to an extent to which they could not have been lawfully closed on the said date.