State of the Beach/State Reports/MN/Shoreline Structures
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DNR Waters has a publication Shoreline Alterations: Riprap, What can I do to keep my shoreline from washing away? This document discourages use of shoreline armoring:
"Protecting your shoreline from erosion may not require you to replace natural shoreline with a high-cost, highly engineered retaining wall or riprap. There are affordable, low-impact methods to stabilize your shoreline and still protect property values, water quality, and habitat. The Minnesota Department of Natural Resources (DNR) encourages you to consider planting native vegetation to control shoreline erosion, enhance aesthetic values, and contribute to better water quality in your lake (see Lakescaping information sheet). Both riprap and retaining walls can reduce erosion, but they can be expensive and negatively affect lakes by creating a barrier between upland areas and the shoreline environment. Riprap should only be used where necessary and never to replace a stable, naturally vegetated shoreline."
DNR also has the following discussion on Riprap:
What is riprap, what is it used for, and do I need a DNR permit to install it?
- Riprap is the term used for large natural rock placed along a shoreline to control or stop erosion. Riprap can be either large boulder size rocks typically found along a farmer's fence line or a commercially mined rock product such as basalt (traprock).
A DNR public waters work permit (application available under DNR Division of Waters forms) is not required if the following conditions are satisfied:
- Installation allowed only where there is a demonstrated need to stop existing erosion or to restore and an eroded shoreline. The DNR area hydrologist should be consulted to determine whether a need for riprap exists.
- The riprap does not cover emergent vegetation, unless authorized by an Aquatic Plant Management Permit from the Department's Division of Fisheries;.
- Only natural rock is used, between 6 and 30 inches in diameter, free of debris that may cause pollution or siltation.
- A filter of crushed rock, gravel or filter fabric material is placed underneath the rock.
- No more than 6 feet waterward of the Ordinary High Water Level
- Conforms to natural alignment of shore and does not obstruct navigation or the flow of water.
- Minimum finished slope no steeper than 3:1 (horizontal to vertical)
- No more than 200 feet of shoreline along lakes and wetlands, or along shorelines of streams, less than 5 times the average width of the affected watercourse.
- Site is not a posted fish spawning area, designated trout stream, nor along the shore of Lake Superior.
Important: Other approvals may be required from federal, state, and local units of government, including the U.S. Army Corps of Engineers, watershed districts, water management organizations, counties, townships, and cities.
Also see Stabilizing Your Shoreline to Prevent Erosion from University of Minnesota Extension.
Information on the extent of shoreline armoring in Minnesota was not readily available.
Several Lake Superior Shoreline Stabilization projects were conducted from 1991 to 1995 involving the installation of blast rock, buttress rock and armor stone to stabilize over a cumulative one mile of shoreline in Lake County.
The Fiscal Year 2017 Civil Works Budget for the U.S. Army Corps of Engineers provides $4.62 billion in gross discretionary funding for the Civil Works program. This budget lists proposed projects and the associated budget justification by state.
Public Education Program
DNR's Restore Your Shore is a powerful multimedia program for shoreland owners and professionals to use in implementing shoreland restoration and protection projects. The Restore Your Shore online program guides property owners through the process of protecting a natural shoreline or restoring a degraded shore with a natural buffer zone.
Living on the Coast, from the U.S. Army Corps of Engineers, describes how natural processes affect the coast, including changes in lake levels, storms and storm surges, waves and wave climate, transport of sediment, ice on the shore, shoreline erosion, lakebed erosion, and movement of water on the land. The booklet also describes how to protect coastal investments by adapting to natural processes, restoring a natural shoreline, moderating coastal erosion, armoring the shore, stabilizing bluffs and banks, controlling surface water and groundwater, building environmentally friendly shore protection structures, and working with engineers and contractors. The final section covers risk management and the economics of protecting your coastal investment, including shoreline property features and value, government regulations to protect a coastal investment, costs of shore protection, and accounting for climate change.
Area Hydrologist (St. Louis and Carlton Counties):
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