Rule E: Floodplain Alteration

1.Policy.

It is the policy of the Board of Managers to:

• (a) Protect the lives and property values of persons occupying the flood plains.
• (b) Enhance the floodplains water resource values. Water resource values are defined as those characteristics which promote the natural moderation of floods, maintain the streams water quality, and provide groundwater recharge.
• (c) Promote the living resource values existing in flood plain areas which include the protection of fish and wildlife resources.
• (d) Enhance the flood plains significant cultural values, which include preservation of open space, natural beauty, areas for scientific study, outdoor education, and recreation.

2. Regulation.

No person may alter or fill land below the 100-year flood elevation of any public water, public water wetland or other wetlands without first obtaining a permit from the District.

For permitting purposes the District is divided into Flood Plain Management Sector A and Sector B. These sectors aid in applying management principles which reflect the hydrologic importance of flood plain across the District.

3. Criteria For Floodplain Alteration.

Permitting Requirements for Flood Plain Management Sector A

Sector A contains those subwatersheds where the percentage of flood plain to total area is twelve percent or less, and the topography in terms of a generalized slope condition is predominantly greater than twelve percent. Flood Plain Management Sector A includes subwatershed 4, 5, 7, 8, 13a, 14a, 14b, 14c, 14d, 14e, 15b and 16.

• (a) Construction of impervious areas within flood plain areas will not be allowed within the designated groundwater recharge areas for the Prairie du Chien-Jordan formation except for road construction, trails, and other recreational improvements.
• (b) To protect water quality and the conveyance capacity of the flood plain, the District will not permit site development which would involve the outside storage of soluble, toxic, or buoyant materials. Examples of acceptable flood plain uses include open space, golf courses, and parking surfaces located outside of designated recharge areas with less than six inches of flooding occurring over the surface.
• (c) Encroachment within the 100-year flood plain may occur if all the following conditions exist:
  • (1) The flood plain storage volume after encroachment is equal to or greater than the flood plain storage volume prior to encroachment (compensatory storage is required).
  • (2) This encroachment does not lie within the floodway and does not result in a violation of the District’s Wetland Alteration Rule F.
  • (3) Construction or development subject to flood damage will have a minimum floor elevation of two feet above the 100-year flood profile.
  • (4) Any structures, facilities, or embankments within the flood plain will be capable of passing the 100-year flood without increasing the elevation of the 100-year flood profile or creating excessive velocities as determined by the District Engineer.

Permitting Requirements for Flood Plain Management Sector B

Sector B contains those subwatersheds where the percentage of flood plain to total area is greater than twelve percent, and the topography is characterized by a general slope condition of predominantly less than twelve percent. Flood Plain Management Sector B includes subwatersheds 1, 2, 3, 6, 9, 10, 11, 12a and 12b.

• (a) Construction of impervious areas will not be allowed within the designated groundwater recharge areas of the Prairie du Chien-Jordan formation except for road construction, trails, and other recreational improvements.
• (b) To protect water quality and the conveyance capacity of the flood plain, the District will not permit site development which would involve the outside storage of soluble, toxic, or buoyant materials. Examples of acceptable flood plain uses include open space, golf courses, and parking surfaces located outside of designated recharge areas with less than six inches of flooding occurring over the surface.
• (c) Encroachment may occur in the flood plain areas of Flood Plain Management Sector B if all the following conditions exist:
  • (1) The encroachment lies within the floodway fringe area of the 100-year flood plain in those areas where floodway has been identified, or in the absence of an established floodway, compensatory (live) storage is excavated.
  • (2) The encroachment does not result in increasing the 100-year flood profile within the floodway portion of the flood plain by more than 0.5-foot or create velocities exceeding 2.5 feet/second or as determined by the District Engineer.
  • (3) The encroachment does not violate the principle of “equal encroachment.”
  • (4) The encroachment does not result in violation of the District’s Wetland Alteration Rule F.
  • (5) Structures and facilities subject to flood damage built within the 100-year flood will have two feet of freeboard between the lowest floor and the 100-year flood profile.

4. Drainage Easements.

Applicant will provide drainage and flowage/ponding easements over flood plain areas inundated during the 100-year flood and drainage easements within 100 feet from the centerline of Rice Creek, Hardwood Creek, Clearwater Creek, and Ramsey County Ditch #2, within fifty feet of the centerline of county and judicial ditches, or within twenty-five feet of the centerline of any major drainageway of the District.

5. Required Exhibits.

The following exhibits must accompany the permit application. One set, full size; two sets, reduced to maximum size of 11” x 17”.

• (a) Site plan showing property lines, delineation of the work area, existing elevation contours of the work area, ordinary high water elevation, and regional flood elevation. All elevations must be reduced to NGVD (1929 datum).
• (b) Grading plan showing any proposed elevation changes.
• (c) Preliminary plat of any proposed land development.
• (d) Determination by a professional engineer or qualified hydrologist of the local 100-year flood elevation before and after the project.
• (e) Computation of change in flood storage capacity resulting from proposed grading.
• (f) Erosion Control Plan.
• (g) Soil boring results if available.