Site Assessment methods for erosion control structures on streams

Site Assessment methods for erosion control structures on streams. Site Assessment methods for erosion control structures on streams. Applicants and department staff shall use 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 streams. (1) Calculation of stream bank erosion potential index. The department shall provide applicants with worksheets and a web page calculator for the purpose of calculating the bank erosion potential index (BEPI). When the department or applicants assess erosion at the bank stabilization site, they shall apply methods outlined in the BEPI worksheet in Table 1 to calculate a BEPI score. For each continuous treatment site of 300 feet or less, applicants shall submit at least one BEPI assessment. For continuous treatments greater than 300 feet, applicants shall conduct and submit BEPI assessments at 150-foot intervals along the treatment site. (2) Bank edge recession measurements. (a) Methods of measuring bank edge recession shall include all of the following: 1. Establishment of a physical measurement reference line between at least 2 headstakes. 2. Date-imbedded photographs showing the initial installation of the reference line and headstakes. 3. Reference distance measures to the bank lip. 4. Time between separate measurements of 3 months or more during the open-water season. (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. (c) As an alternate to the recession measurement methods identified in par. (a) or (b) , the severity of shoreline erosion can 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. The average annual rate of lateral migration shall be measured at the apex of the channel bend using 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.