Whenever it appears to the State Government that injury to any land or the public health or public convenience has arisen or may arise from the obstruction of any river, stream or drainage-channel, such Government may, by notification published in the Official Gazette, prohibit, within limits to be defined in such notification, the formation of any obstruction, or may, within such limits, order the removal or other modification of such obstruction.
     Thereupon so much of the said river, stream or drainage -channel as is comprised within such limits shall be held to be a drainage-work as defined in section 3.