Keweenaw County: Lake Superior shoreline erosion study - Summary and Maps

Contacts:    Kate Lederle lederlek@michigan.gov 517-284-5564

   Jim Milne milnej@michigan.gov 517-284-5559

 

The DEQ Water Resources Division (WRD) conducted an update of its shoreline recession rate study of the Lake Superior shoreline in Keweenaw County.  The original shoreline recession rate study was conducted in 1983.  Changes in the high-risk erosion area (HREA) boundaries and projected shoreline recession distances are proposed.  Letters explaining the proposed changes and information regarding the opportunities for input have been sent to property owners, local officials and legislators. A webinar and a local public meeting are planned for August 1 and August 9, 2017, respectively. The webinar will be held at 2:30 p.m. EDT. Registration is required online at www.mi.gov/shorelands, select “Keweenaw County:  A webinar to discuss the latest Lake Superior shoreline erosion study.” or put the following link into your internet browser https://attendee.gotowebinar.com/register/3010147660827463683. The public meeting will be held in the Courtroom at the County Courthouse, 5095 4th Street in Eagle River at 6:30 p.m. Property owners have until September 8, 2017 to provide comments before the final HREA designations will be established by certified mailings to the affected property owners.  The affected property owners have sixty days from the receipt of their designation letter to appeal the designation.

The HREA program identifies rapidly eroding coastal reaches and establishes setback requirements for construction in these hazard areas to prevent property loss. The proposed changes in the HREAs are the result of a recession rate study conducted on March 14, 2017 to identify changes in the long-term rate of erosion occurring along the Great Lakes shoreline pursuant to R 281.22 (22) of the Great Lakes Shorelands Administrative Rules promulgated pursuant to Part 323, Shorelands Protection and Management, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended (Part 323). The study identified shorelines where recession is occurring at an average rate of at least one foot per year over a minimum of 15 years.  A longer study time period was used when technically possible to span a wider range of water levels and shoreline fluctuations.

 

The Update Study

The erosion hazard line (EHL) as defined in R 281.21 (1) (c) means the line along the shoreland that is the landward edge of the zone of active erosion or the line where the 604.4 feet, 1985 International Great Lakes Datum, contour on Lake Superior meets the shoreland, whichever is furthest landward.  The zone of active erosion means the area of the shoreland where the disturbance or loss of soil and substrate has occurred with sufficient frequency to cause unstable slopes or prevent vegetation of the area [R 281.21 (1) (r)]. The recession rate study compared the EHL on historical aerial photographs to the EHL on modern aerial photographs.  Historic aerial imagery from 1980 was used for the shoreline in Allouez, Houghton, Eagle Harbor and southern Grant Townships. In Sherman Township and northern areas of Grant Township imagery from 1977 was used.  The modern imagery was from 2015. The study spanned periods of 35 and 38 years, respectively.

The historic EHL was determined by viewing the vegetation lines along the shoreline on the aerial photograph.  The modern EHL was determined using the same method with the added information provided by low-level oblique aerial photographs, 2012 USACE Great Lakes Oblique Imagery, which shows detailed views of the shoreline from an offshore vantage point.  An additional resource was the Great Lakes Shoreline Geodatabase, which gives the approximate location of areas of various bluff heights among other attributes.  Cross-referencing these resources with the modern imagery was helpful in determining the modern EHL. The shoreline was reviewed and the EHL was determined for all previously designated HREAs and areas of apparent erosion.

Transects were drawn perpendicular to the shoreline at 150 foot intervals along the shoreline and recession rates calculated along the transect lines. Similar rates were grouped into high risk erosion areas (Area).  Average recession rates were calculated within each Area. Projected recession distances were determined for each Area.  Parcel boundaries and owner data was received from the Keweenaw County Equalization Department. The current Area and parcel data were compared to the 1983 data to determine designation changes.

Within these hazard areas, placement of new construction requires a permit and must meet setback distances based on projected recession distances when combined with the type of construction and other site specific conditions.  The projected recession distance is the calculated rate of recession for the area over a 30 year [for readily moveable structures, as defined in R 281.21 (1) (k)] or 60 year [for permanent structures, as defined in R 281.21 (1) (i)] period as determined by R 281.22 (2).  The required setback distance is based on this rate but may be greater in areas of bluffs over 25 feet in height.

Affected parcels were classified under one of the following three categories:

De-designation:  These are parcels where the average rate of recession was documented to be one foot per year or greater during the previous study; however, the current study found the long-term rate of recession has fallen below the one‑foot‑per‑year threshold required for HREA designation.  The HREA designation is therefore removed, also eliminating the regulations and permit requirements under Part 323.

New:  These parcels were not designated during the previous study as being in an area of high risk erosion; however, the current study found the long-term rate of recession has increased to, or is above, the one-foot-per-year threshold required for HREA designation.  The properties are designated and subject to the regulations and permit requirements under Part 323 and promulgated rules for high risk erosion areas.

Lower:  These are parcels where the average rate of recession was documented to be greater than one foot per year during the previous study and are currently designated as being in an HREA.  The current study documented a decrease in the long-term recession rate, but the erosion rate is still at or above one foot per year resulting in a decrease in the projected recession distances.

 

Preliminary Findings

There are approximately 92 miles of Lake Superior shoreline in Keweenaw County among five townships: Allouez, Houghton, Eagle Harbor, Grant, and Sherman. The entire shoreline was viewed using the USACE 2012 oblique imagery to determine study sites. Field work included measuring points along Great Sand Bay at the public access. During the current study 25% (23 miles) of the shoreline was identified as needing study because it was either previously designated or showed signs of erosion. Of the shoreline studied 2.6% (0.6 miles) was determined to be in an area of high risk for erosion.  Of the currently identified areas of high risk erosion 81% (0.5 miles) will be designated for the first time.  In 1983, approximately 4 miles of Keweenaw County shoreline was designated as being at high risk for erosion.  Of the originally designated shoreline 3% (0.11 miles) remain designated. Nearly four miles of shoreline will be de-designated.

The study will affect a total of 114 parcels.  Five parcels will be newly designated in Keystone Bay, five parcels in Great Sand Bay and one parcel in Keystone Bay will have lower projected recession rates.  A total of 103 parcels will be de-designated and will no longer require new structures, or their additions, to be setback a specific distance from the erosion hazard line per Part 323.  Preliminary High Risk Erosion Area Update maps are available for review at the links at the bottom of this page.

Allouez Township – The study determined all previously designated properties are no longer eroding at a rate of one foot or greater on average.  These parcels will be de-designated. No new parcels will be designated in the township.

Houghton Township - The north-facing shoreline of Great Sand Bay had one stretch of shoreline where the rate of erosion continues to be above the regulatory 1 foot per year however the rate of erosion declined from 1.7 feet per year to 1.2 feet per year.  The highest recession rate in the county is in Great Sand Bay.  The projected 30-year recession distances decreased from 65 feet to 50 feet. The projected 60-year recession distance decreased from 115 feet to 85 feet.  Previously designated areas not found to be eroding at an average rate of one foot or greater will be de-designated.

Eagle Harbor Township – The study determined all previously designated properties are no longer eroding at a rate of one foot or greater on average.  These parcels will be de-designated. No new parcels will be designated in the township.

Grant Township - The shoreline continues to have areas of erosion. The maximum average rate of erosion is 1.1 feet per year with a projected 30- and 60-year recession distances of 50 feet and 80 feet, respectively. On one parcel the rate decreased from 1.2 feet per year to 1.1 feet per year. Five parcels were newly designated.

Sherman Township – The shoreline was not found to be receding at a rate of greater than 1 foot per year over the study period for the township.

 

Public Meetings and Notification

A public webinar will be conducted from Lansing and a public meeting and a meeting with local officials will be held in Eagle River to explain the high risk erosion program and the current recession study to local officials and property owners.  Prior to these meetings legislators will be sent written notification of the WRD’s proposed action. The meeting with local officials will include building code and zoning officials, sanitarians, and other affected local governmental agencies.  These meetings provide WRD staff an opportunity to explain the pending regulatory changes by presenting information and maps showing the current HREA boundaries, recession distances, and proposed changes. Through these meetings, local officials and property owners have an opportunity to discuss concerns, provide additional information and ask questions.

The information gathered at these meetings will be incorporated into the final recession rate studies and projected recession distances.  WRD staff will address all comments and concerns prior to implementing the proposed HREA designations.

The final phase consists of certified mailings, R 281.22 (3), sent to the owners of affected properties.  These letters establish the designations proposed in the first mailing and discussed with property owners and local officials.  Property owners have up to sixty days from their receipt of the certified mailing to submit appeals of the WRD’s actions.  WRD staff will review the property owner’s concerns, make adjustments if appropriate, or proceed with an administrative contested case hearing.

 

Preliminary Maps

Allouez Township (North), De-designated

Allouez Township (Central), De-designated

Allouez Township (South), De-designated

Eagle Harbor Township, De-designated

Grant Township (Betsy Bay), De-designated

Grant Township (Keystone Bay), HREA

Houghton Township (Great Sand Bay), HREA