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how Wisconsin protects waterways by holding them in trust for everyone to enjoy.
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Waterway and wetland permits: calculating energy along a shoreline

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Follow these steps to obtain an accurate calculation of energy along your shoreline:

  1. Print out the map for your lakeshore site (include the scale)
  2. Figure out the correct feet-per-inch value using the map scale and your ruler, and enter the number here: 1 inch = feet
  3. Mark your shoreline site on the lake map.
  4. Draw the longest unobstructed straight line originating from your site across the water to any other point on the shore; this is the fetch at your site. Use this example [PDF, 289KB] for reference.
  5. Using a ruler, measure the length of the fetch line and record this value: inches
  6. To convert the ruler measurement of fetch to actual distance, multiply feet per inch (found in step 2) by the measured fetch line (found in step 5):
    Lake Fetch = feet/inch x inches = 0 feet or Miles
  7. Measure the mean depth along your fetch line
    1. Locate and mark at least 5 equally-spaced points along your fetch line.
    2. Estimate and record the depths at these equally spaced points (for example: 45 ft, 105 ft, 75 ft, 55 ft and 25 ft).
    3. Add these depth values together and then divide by the number of sample points taken, and record the result. For example, (45 ft + 105 ft + 75 ft + 55 ft + 25 ft)/5 = 61 feet.) Use this example [PDF, 273KB] for reference.
  8. Using the two values obtained in steps seven and eight, fetch from your siteThe lake fetch from your site is the longest continuous distance originating from your shore across the water surface to the opposite intersection with the shore or land. and mean depth on your fetch lineThe mean depth along your fetch line is the average depth of water between your shore and the opposite shore or land., use the wind wave model below to calculate the storm wave height at your site. The storm wave height is used to determine the energy categoryLess than 1 foot = Low Energy
    Between 1 and 2.3 feet = Moderate Energy
    Greater than 2.3 feet = High Energy
    at your site.

Lake fetch from my site Miles (found in step 6)

Mean water depth along my fetch Feet (found in step 7)

Storm wind speed 51.33 ft/sec


Non-dimensional fetch = 


Non-dimensional water depth = 


Non-dimensional epsilon = 


Wave energy/length weight = --

Storm wave height =  feet

Energy category = Low energyModerate energyHigh energy

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Last revised: Wednesday December 02 2015