Land-disturbing activities for construction in, on, over, or under a lake or natural watercourse shall be planned and conducted so as to minimize the extent and duration of disturbance of the stream channel or lakebed. Where relocation of a stream is an essential component of the proposed activity, the relocation shall be planned and executed so as to minimize changes in the stream flow characteristics, except where the developer or landowner demonstrates to the Planning Director that significant alteration to the flow characteristics is justified.