Subject to any rules made in this behalf, any person, generally or specially authorised by the Authority in this behalf, may, whenever it in necessary so to do for any of the purposes of this Act, at all reasonable times, enter upon any land or premises and--
     (a) make any inspection, survey, measurement, valuation or inquiry;
         (b) take levels;
         (c) dig or bore into sub-soil;
         (d) set out boundaries and intended lines of work;
         (e) mark such level boundaries and lines by placing marks and cutting trenches; or
         (f) do such other acts or things as may be prescribed:
     Provided that no such person shall enter any building or any enclosed court or garden attached to a dwelling-house (unless with the consent of the occupier thereof) without previously giving such occupier at least twenty-four hours' notice in writing of his intention to do so.