Property owners occasionally return to their cabins in the spring only to discover they are dealing with property damage caused by a phenomenon called "ice heaving" or "ice jacking". This powerful natural force forms a feature along the shoreline known as an "ice ridge". The result may include significant damage to retaining walls, docks and boat lifts, and sometimes even to the cabin itself.
The cause of ice ridges:
Ice damage to shoreline property is often caused by the "pushing" action of an ice sheet. Cracks form in ice because of different contraction rates at the top and bottom of the ice sheet. This is especially true in years lacking an insulating snow cover. Ice cracks also develop because the edges of the ice sheet are sometimes firmly attached to the shoreline. When water rises in the cracks and freezes, the ice sheet expands slightly. When rising air temperature warms the ice, the additional expansion exerts a tremendous thrust against the shore. The expanding ice sheet moves soil to create ice ridges (also know as "ice pushes" or "ramparts") as high as five feet or more. Alternate warming and cooling of an ice sheet causes additional pushing action that possesses enough power to nudge masonry bridge piers out of plumb and push houses off their foundations.
For more information about this brawny natural force see:
- DNR Waters Information Sheet on Ice Ridges
- ICE! ... Blockbuster by Boreas! Sidney A. Frellsen, Conservation Volunteer Magazine, January-February 1963
- ICE POWER! Gerald L. Paul, Water Talk Newsletter, Spring 1987
- Ice Damage Photo Gallery
What can be done after an ice ridge has formed:
The question arises ... Is a DNR permit required to remove or grade soil material (ice ridge) pushed up by ice action onto my shoreline?
Near-shore areas are critical to the health of a water body's ecosystem. Therefore, for most projects involving work below the ordinary high water level (OHWL) of public waters, an individual Public Waters Work Permit is required.
Minnesota rules allow for some exceptions with regard to ice ridges. An individual Public Waters Work Permit would not be required from the DNR for ice ridge removal or grading under the following conditions:
- The ice ridge resulted from ice action within the last year;
- The project is either exempt from local permits or is authorized by issuance of a local government permit;
- Not more than 200 feet of shoreline is affected;
- All ice ridge material that is composed of muck, clay or organic sediment is deposited and stabilized at an upland site above the ordinary high water level (OHWL);
- All ice ridge material that is composed of sand or gravel is removed as provided above or graded to conform to the original cross-section and alignment of the lakebed, with a finished surface at or below the ordinary high water level (OHWL);
- No additional excavation or replacement fill material occurs on the site;
- All exposed areas are immediately stabilized as needed to prevent erosion and sedimentation; and
- Local zoning officials, the Watershed District, if applicable, and the Soil and Water District are given at least seven days prior notice.
For more information, contact your local DNR Waters Area Hydrologist .