Download the full Floodplain Alteration Rule (PDF).

Adopted April 11, 2024
Effective April 29, 2024


It is the policy of the Board of Managers to:

(a) Preserve flood storage capacity between the ordinary and 100-year high water elevations of waterbodies to limit flood frequency and severity;

(b) Limit flood risk for structures built in or adjacent to floodplain;

(c) Protect streambanks for stability, water quality and ecological values.


(a) A permit is required to fill, excavate or grade within the floodplain of a waterbody.

(b) For all work requiring a permit under paragraph 2(a), a structure intended for residential, commercial, industrial or institutional occupancy must be constructed so that door and window openings are at least two feet above the 100-year high water elevation of the waterbody.


(a) A permit is not required for soil cultivation, soil amendment, or topsoil or sod addition for ordinary landscaping purposes.

(b) If the floodplain of a waterbasin lies entirely within a municipality, the waterbasin does not outlet during the 100-year event, and the municipality regulates floodplain encroachment, a District permit under this rule is not required.


Fill, excavation or grading must conform to the following standards:

(a) Any floodplain fill must be offset so there is no loss in flood storage between the ordinary high water and 100-year high water elevations.  There may not be net positive fill at any time during the work, unless applicant has demonstrated it is impractical and has obtained District approval of a sequencing plan for which applicant’s registered professional engineer has demonstrated that the No-Rise Standard is met.

(b) Offset for fill in a waterbody other than a watercourse is not required if the applicant demonstrates that fill on all riparian properties to the extent proposed by the applicant would meet the No-Rise Standard and not restrict flood flows.

(c) Fill in a watercourse must meet the following criteria:

  1. No impervious surface may be placed within the 10-year floodplain or within 25 feet of the watercourse centerline, whichever greater, unless the surface is: (1) no more than 10% of the site 10-year floodplain area; or (2) a linear component of a public roadway or trail.
  2. Applicant must meet the No-Rise Standard.

(d) Ice ridge grading within a waterbasin must conform to the pre-existing basin cross-section.  Soil material may be neither imported into nor removed from the floodplain.


The following submittals must accompany the permit application:

(a) Site plan showing property lines, delineation of the work area, existing elevation contours of the work area, and ordinary high water (OHW) and 100-year high water elevations. All elevations must be reduced to NGVD (1929 datum).

(b) Grading plan with proposed elevation changes.

(c) Preliminary plat, if applicable.

(d) Professional engineer registered in the State of Minnesota’s determination of the 100-year high water elevation before and after the project and, if paragraph 4(c) applies, of the edge of the 10-year watercourse floodplain.  A DNR No-Rise Certificate may be submitted to document conformance with the No-Rise Standard, where applicable.

(e) Computation by a professional engineer, architect, land surveyor or landscape architect of volumes of floodplain fill and excavation and, if paragraph 4.c applies, of impervious surface area adjacent to a watercourse.

(f) If not otherwise subject to the District erosion control rule, an erosion control plan conforming to sections 5, Erosion Control Plan, and 9, Maintenance, of that rule.

(g) If more than 50 cubic yards of fill have been placed, on project completion applicant must submit an as-built survey prepared by a professional engineer, architect, land surveyor or landscape architect documenting locations of floodplain disturbance and the volumes of fill and created flood storage.