No person shall place or cause to be placed any fill in any area below the mean high water level of any public waters or below the artificially-created high water level of publicly-owned bodies of water in this state with the intent or with the effect of creating or forming filled land adjacent to such bodies of water, except as provided in this subdivision. For the purposes of this subdivision, “public waters” means all natural ponds of more than 10 acres, and “publicly-owned bodies of water” or “public-owned water bodies” means those bodies of water whose artificial high water level is maintained by the state’s exercise of its flowage rights on these ponds. The provisions of this subdivision shall not apply to such minor improvements of shorelines as the department, by rules adopted by the commissioner under RSA 541-A, may allow.