NR 320.07(2)(b)3.3. Institutional permanence of a duration similar to the life of the structure. NR 320.07(3)(3) Standards. The department may issue a permit for a breakwater under this section if all of the following conditions are met: NR 320.07(3)(a)(a) A breakwater is determined by the department to be the best management practice to control shore erosion and preserve or restore aquatic habitat, considering efficacy of the structure and impacts to the public interest in navigable waters. NR 320.07(3)(b)(b) The breakwater is designed by an engineer licensed or certified to practice in this state under ch. 443, Stats., to be stable under stated maximum water level and wave conditions to avoid a failed structure that quickly becomes a hazard to users of the waters. NR 320.07(3)(c)(c) The breakwater is specifically recommended for the purpose specified in par. (a) in a comprehensive plan approved by the department for management of a specific water body and its watershed. NR 320.07(4)(4) Permit conditions. In addition to any conditions determined by the department to be necessary to protect public rights and interests in navigable waters under s. 30.12, Stats., any permit issued by the department under this section shall contain all of the following conditions: NR 320.07(4)(a)(a) The breakwater shall remain under public ownership or control by a public entity described under sub. (2) (a). Public ownership and control, including necessary rights to use and management of the breakwater and the area to be protected from wave energy by the breakwater shall be established by documentation of any of the following as part of the permit application: NR 320.07(4)(a)2.2. Lease of the breakwater to a public entity described under sub. (2) (a) with a term of 25 years or more. NR 320.07(4)(a)3.3. A conservation easement on the breakwater held by a public entity described in sub. (2) (a) that includes the rights to construct and maintain the structure and the right of public access to the structure. NR 320.07(4)(b)(b) No ancillary structures or facilities, other than scientific measuring devices and navigational markers, shall be located on or attached to the breakwater. NR 320.07 HistoryHistory: CR 24-051: cr. Register January 2026 No. 841, eff. 4-1-26; correction in (3) (b) made under s. 35.17, Stats., Register January 2026 No. 841. NR 320.08NR 320.08 Navigability standards for bridges and culverts. NR 320.08(1)(1) A new bridge or culvert or replacement of an existing bridge or culvert spanning a navigable waterway regulated under this chapter shall, except as provided in this section, maintain a clearance of not less than 5 feet. NR 320.08(2)(2) The department may require clearance of more than 5 feet when the waterway has been or is likely to be navigated when the waterway is above its ordinary high water mark elevation or if it is used by watercraft or snowmobiles requiring greater clearance. NR 320.08(3)(3) The department may allow less than 5 feet of navigation clearance for a bridge or culvert when the department determines all of the following apply: NR 320.08(3)(a)(a) The waterway is known by the department to have little or no snowmobile use or navigation, other than by watercraft capable of using a portage established under par. (b). NR 320.08(3)(b)(b) The owner provides a permanent portage, identified by signage, over or around the bridge or culvert. NR 320.08(3)(c)(c) The reduced clearance will not be detrimental to the public interest, as determined by the department. NR 320.08 HistoryHistory: CR 24-051: cr. Register January 2026 No. 841, eff. 4-1-26. NR 320.09NR 320.09 Riparian rights determinations. In order to determine whether a pier or boat shelter interferes with the rights of an adjacent riparian, a riparian may use any of the following methods they determine most fully meets the Wisconsin supreme court ruling in Rondesvedt v. Running, 19 Wis. 2d 614 NR 320.09(1962)(1962), that “. . . each must have his due proportion of the line bounding navigability and a course of access to it from the shore exclusive of every other owner, and that all rules for apportionment or division are subject to such modification as may be necessary to accomplish substantially this result.” NR 320.09(1)(1) Apportionment of the line of navigation. The general procedure for the apportionment of the line of navigation is to measure the whole shoreline of the cove or bay and the line of navigation in front of the shoreline and to apportion the line of navigation among the riparians in proportion to the length of their respective holdings on the shoreline. The area of water within which each riparian may place a pier to reach the line of navigation is determined by drawing straight lines between the corresponding points of division on the shoreline and the line of navigation. NR 320.09(2)(2) Coterminous riparian rights lines. Under the coterminous riparian rights lines method, chords are drawn to connect points established at the intersection of each lot line with the ordinary highwater mark. The lines that bisect the angle formed by adjacent chords are the coterminous riparian rights lines. The extension of the coterminous riparian rights lines to the line of navigation describes the portion of the water within which each riparian may place a pier to gain access to the line of navigation. If the coterminous riparian rights lines intersect before the line of navigation is reached, another method of apportionment will be used. NR 320.09(3)(3) Extended lot lines. Under the extended lot line method, the area of water within which each riparian may place a pier to reach the line of navigation is determined by extending the lot lines along the same alignment from the upland to the line of navigation. NR 320.09(4)(4) Other methods. Any other method for determining the rights of riparians to gain access to the line of navigation that is consistent with sub. (1). NR 320.09 HistoryHistory: CR 24-051: cr. Register January 2026 No. 841, eff. 4-1-26. NR 320.10NR 320.10 Culvert sizing. Project proponents and department staff shall use any of the following calculation and assessment methods for potentially exempt culverts under s. NR 320.04 (10) and culvert individual permit applications under s. NR 320.06. NR 320.10(1)(1) Calculation of required culvert area. To determine the required culvert area, measurements shall be made of the channel width of the stream in feet at the bankfull width (W), and the maximum bankfull height in feet above the stream bottom (H) (see diagram). These measurements shall be made at each of 3 locations or transects along the stream: the location of the newly proposed culvert crossing; 100 feet upstream from the crossing; and 100 feet downstream from the crossing. Where there is an existing crossing being replaced, measurements at the site of the crossing may not be representative due to impacts related to the existing crossing. In such instances two measurements shall be taken, upstream and downstream of the crossing location. Measurements shall be taken to ensure that the locations where measurements are made are representative of the stream overall. The individual measurements of W and H shall be averaged to derive the final W and H values. The required culvert area is then calculated with the following equation: Required Culvert Area (square feet) = H x W NR 320.10(2)(2) Culvert sizing. Once the required culvert area has been determined, the applicant can identify the proper culvert size by reviewing Table 1 for round culverts and Table 2 for arched pipe culverts. The minimum size culvert needed to pass flows shall have an area that is as much or more than the required culvert area. For example, the recommended culvert size for a culvert area calculation of 8.50 square feet would be 42 inches. NR 320.10(2)(a)(a) To find the area of any round culvert, use the following equation: Round Culvert Area (square feet) = R x R x 3.14
R (radius in feet) = Culvert diameter (inches) / 24
Culvert size required for a stream with a culvert area calculation of 8.5 square feet:
8.5 square feet = R x R x 3.14
2.7 square feet = R x R
1.6 feet = R
R = 19.7 inches
Culvert diameter = 39.4 inches
Culvert size = 42 inches
NR 320.10(3)(3) Culvert length determination. The proper culvert length is determined by the following calculation: NR 320.10(3)(a)(a) To determine the length of any culvert, use the following equation: L (Length of Culvert) = W + 4H + 2
W = Width of road top
H = Height of culvert + average depth of road fill
H is multiplied by 4 as a constant for the side slope angle (2 x 2:1)
2 is added as a constant for 1 foot of pipe extension beyond fill
Length of culvert needed for 10’ road top, 24” (2”) diameter pipe, 1’ average road fill depth, 2:1 side slopes, 1’ pipe extension beyond fill:
L = 10’ road top + 4(2’ culvert + 1’ fill) + 2’ extension
L = 10 + 4(2+1) + 2
L = 10 + 4x2 + 4x1 + 2
L = 10 + 8 + 4 + 2
L = 24 feet
NR 320.10 HistoryHistory: CR 24-051: cr. Register January 2026 No. 841, eff. 4-1-26. NR 320.11NR 320.11 Site assessment methods for erosion control structures on inland lakes and flowages. Applicants and department staff shall use any of the following data requirements and site assessment methods for potentially exempt riprap under s. NR 320.04 (12) and shoreline erosion control structures individual permit applications under s. NR 320.06 for inland lakes and flowages: NR 320.11(1)(1) Calculation of storm-wave height. The department shall provide applicants with worksheets and a web page calculator for the purpose of estimating storm-wave height. The storm-wave height calculator shall be mathematically designed based on Young and Verhagen (1996) and Young (1997) by applying a storm wind speed of 35 miles per hour (51.45 ft/sec), fetch at the applicant’s shore protection site, and the average depth along that fetch. To record fetch, applicants shall measure the longest unobstructed straight-line distance originating from the shore protection site across the water surface to the opposite intersect with the shore. To estimate average depth applicants shall examine a lake map, sum the reported depths along the fetch, and divide by the number of recorded values. At least 5 equally placed intervals along the fetch shall be used. NR 320.11 NoteNote: To use a web version of the storm-wave height calculator, go to dnr.wisconsin.gov, keyword “calculating energy along a shoreline.”
NR 320.11 NoteNote: The citation for Young (1997) is as follows: Young, I.R. 1997. The growth rate of finite depth wind-generated waves. Coastal Engineering, Vol. 32, pp. 181-195. The citation for Young and Verhagen (1996) is as follows: Young, I.R. and L.A. Verhagen. 1996. The growth of fetch limited waves in finite water depth. Coastal Engineering, Vol. 29, pp. 47-78.
NR 320.11 NoteNote: Statewide storm wind speeds are estimated from Naber Knox, P. 1996. Wind Atlas of Wisconsin. Wisconsin Geological and Natural History Survey, Bulletin No. 94.
NR 320.11(2)(2) Calculation of erosion intensity. When an applicant or the department believes that, as a result of site conditions, storm-wave height as calculated under sub. (1) may inaccurately predict the degree of erosion, the erosion intensity score may be calculated to determine erosion. The department shall provide applicants with worksheets and a web page calculator for the purpose of calculating erosion intensity. When the department or applicants assess erosion at the shore protection site, they shall apply methods outlined in Table 1 to calculate an erosion intensity score. Wherever erosion intensity and storm-wave height result in different energy categories, the site shall be placed in the category as determined by the erosion intensity score. Table 1. Erosion Intensity (EI) Score Worksheet
NR 320.11 NoteNote: The EI Score Worksheet is adapted from Knutson, P. L., H. H. Allen, and J. W. Webb, 1990. “Guidelines for Vegetative Erosion Control on Wave−Impacted Coastal Dredged Material Sites”, Dredging Operations Technical Support Program Technical Report D−90−13,U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS 39180, 35 pp.
NR 320.11 Note1. Average fetch: The following diagram describes the calculation of average fetch.
NR 320.11 Note2. Bank height: Bank height is the vertical measure (feet) from the bank toe to the top of the bank lip, irrespective of water level changes.
NR 320.11 Note3. Aquatic vegetation: Dense or abundant means that on average 50 to 100% of the bottom is visually obstructed by plants during the growing season, defined by the dates June 1 through September 15. Scattered or patchy means that on average 1 to 49% of the bottom is visually obstructed by plants during the growing season, defined by the dates June 1 through September 15. Absent means that on average < 1% of the bottom is visually obstructed by plants during the growing season, defined by the dates June 1 through September 15.
NR 320.11 Note4. Shoreline orientation: The following lake map shows an example of accurately determining shoreline orientation.
NR 320.11 Note5. Boating: A thoroughfare is identified as physical narrowing of the waterbody that by its nature intensifies boating activity near the shore. Thoroughfares that are 250 yards or wider are not scored 12 points, unless the depth contours of the thoroughfare constrict boating activity in close proximity to one shore and the traffic is intensive. Intensive traffic is defined by a location where at least 50% of the public boating access available must pass through the thoroughfare to reach the open water of the lake, provided the waterway has a total of more than 60 car−trailer units. Limited traffic is defined by a location where at least 30% of the public boating access available must pass through the thoroughfare to reach the open water of the lake, provided the waterway has a total of more than 40 car−trailer units.
NR 320.11(3)(a)(a) Except as provided in pars. (b) and (c), the method of measuring bank edge recession shall include all of the following: NR 320.11(3)(a)1.1. Establishment of a physical measurement reference line between at least 2 headstakes. NR 320.11(3)(a)2.2. Date-imbedded photographs showing the initial installation of the reference line and headstakes. NR 320.11(3)(a)4.4. Time between separate measurements shall be of 3 months or more during the open-water season. NR 320.11(3)(b)(b) As an alternate to the bank edge recession measurements method identified in par. (a), if 2 or more years of LiDAR elevation data are available for a site, the LiDAR elevation data may be used to determine the average annual rate of bank edge recession by comparing the horizontal distance the bank lip has moved using a GPS point and dividing this measurement by the difference in the number of years between datasets. NR 320.11(3)(c)(c) As an alternate to the recession measurement methods identified in par. (a) or (b), the severity of shoreline erosion may be identified using average annual rate, in feet per year, of shoreline recession with measurements from historic aerial imagery over a period of 20 years. This method may be excluded, or the evaluation period abbreviated, if imagery is unavailable or obscured by canopy.
