III. A Natural Border

A. What it is and why it supports coastal resilience  

The characteristics of a shoreline are formed by the interaction between the water’s energy (force and motion), and the land’s material (sand, pebbles, bedrock, vegetation) and arrangement (slope). These elements are constantly working together to reach an equilibrium that allows the material to best receive, absorb, and dissipate the energy of the water. Once again, change is the constant: the water’s force and motion are dynamic, and the land’s material and arrangement continually adapt to them, so this equilibrium is in an uninterrupted state of rebalance. A “natural border” between land and water refers to a shoreline where both the material and the arrangement are relatively free of human alteration. 

Natural shorelines support coastal resilience by allowing the process of rebalance between the water’s force and the land’s accommodation of it to proceed unhindered. In a sense, the land is an active partner here, offering up responses that range from reconfiguring its shape to sprouting up vegetation, depending on conditions. The Resilient Coastal Communities Planning Guide and the Building Coastal Resilience video series (especially part 2) describe how waves and currents move beach sediments over time. Wetlands dissipate great quantities of energy while also providing unique habitats and improving water quality. ^{15 16 17}

B. Why isn’t this already done? 

The short answer is: a philosophical prioritization of engineered processes over natural ones.

People of European heritage are among the cultures that have gone to great lengths to reshape our environment as we’ve seen fit. This has largely been accomplished through an “engineering approach” that focuses on human inputs like research, design, feasibility, and implementation, and considers non-human inputs only to the extent that they constrain or assist the human efforts. 

This approach is not intended to co-operate with natural processes but rather to overcome them as necessary to achieve our aims.  In the coastal context, we have surmounted innumerable types of physical obstacles to attain access to water, a critical resource for settlement. However, the magnitude, dynamic unpredictability, and continuous nature of the water’s force on coastal development has cast doubt on the affordability of maintaining this approach. 

“Nature-based solutions” ¹⁸ and “green infrastructure” ¹⁹ are two terms that refer to alignment of human goals with processes that are occurring in the natural world independently of human investment. A body of research beginning in the late 1990s demonstrates the effectiveness of this approach, and its applications have been increasing over time.  As the benefits of conserving and restoring natural systems and designing new systems to mimic their processes are increasingly measured and quantified, it becomes possible to encourage or require a preference for this approach over the engineering approach.  

The pendulum is swinging ever so slightly away from exclusively recognizing and valuing human intervention. Mounting evidence of the successful outcomes resulting from protecting and restoring natural processes—designing with nature, rather than against it—offers legal support for a regulatory framework that requires it. 

C. What are the shoreline types along the Great Lakes coast?  

The tools in this section support the specific and varied geological characteristics of your community’s shoreline, which shape your unique coastal processes, which in turn affect how to manage them. Here are the six typical Michigan shoreline types described in the Planning Guide:

Elevated: bluffs and banks

Elevated shorelines have a steeply-sloped drop between the water’s edge and the adjacent land. The material consists of a range of sediment sizes left by deposits from the last glaciation, and the relatively low amount of sand means that the beach between the bottom (“toe”) of the bluff and the water’s edge is narrow. In these areas, the elevation change creates distance that protects buildings from flooding. However, the narrow beach means that wave energy is received primarily on the toe of the bluff. Erosion occurs from the bottom up, putting structures at the top of the bluff at risk. 

Sandy beaches and dunes

Sandy beaches tend to have shallow slopes and are typically fed by sandbars close to shore. These shoreline types are especially responsive to water and wind energy, which means that they are especially unstable for building purposes. The shallow slope means that changes in the water level can affect dramatically large swaths of land, causing flooding concerns. Sand is light and mobile, making it an unsteady building surface and also susceptible to erosion. Because sandy soil drains well, any contamination on land is swiftly carried into the waterbody. 

Coarse sediment beaches

Made up of gravel or cobble, these heavier materials mean that the beach remains relatively stable over time, and are less susceptible to erosion than sandy beaches. They are often steeply sloped, with relatively deep water near the shoreline. A steeper slope mitigates flooding by preventing rising water levels from traveling inland. 

Bedrock

Bedrock coasts reflect wave energy, resisting erosion unless the rock type is soft. The elevation and slope are highly variable, depending on the shape of the rock. A shallow slope near the water’s edge may still leave it susceptible to flooding. 

Wetlands

Wetland coasts are covered in mud, silt, and vegetation. They absorb and dissipate wave energy as the root structure of the plants holds the coastal material in place. These areas are wide and flat, making them exceptionally prone to flooding. The vegetation, which is adapted to periodic inundation, helps mitigate this flooding risk both by forming a physical barrier, and by soaking up water and releasing it into the air through the evapotranspiration process. The soft surface makes these areas unsuitable to build on without extensive mitigation, but they can form an excellent natural protective buffer between water and development. 

Artificial / armored

These shorelines have been “hardened” with structures intended to prevent flooding and erosion, an investment that indicates development is in the direct path of one of these conditions. “Armoring” refers collectively to the installation of seawalls, revetments, bulkheads, riprap, and other structures that replace the natural shoreline. In the past, shoreline armoring was viewed as an effective strategy for safeguarding coastal properties and infrastructure, offering immediate, visible protection and providing a sense of security for concerned homeowners, businesses, and municipalities. Early technical guidance on coastal engineering provided by the US Army Corps of Engineers detailed methods and designs for constructing various armoring structures. 

Artificial shorelines carry a continuous burden of maintenance and replacement. They are guaranteed to periodically fail and are likely to occasionally be inadequate. Hardened surfaces reflect wave energy back into the water rather than dissipating it. Armoring structures are generally installed on a property-by-property basis, so reflected energy reaches around the edges of the structure and performs its erosive activity on the unprotected areas. This causes the armoring to loosen and eventually detach. It also distributes the erosive effect onto neighboring property. Armoring creates a steep (often vertical) slope that prevents water from traveling landward, but only as long as the lake level remains below the top elevation of the structure. 

Although armoring is sometimes referred to as “shoreline protection,” this term is inaccurate. Artificial shorelines remove, disturb, and interrupt natural shorelines. They disrupt ongoing coastal processes in a piecemeal fashion, causing effects on not only adjacent properties but throughout the coastal ecosystem. Often, they exacerbate on other properties the problems they purport to solve on the property where they are installed—the very outcome that planning and zoning are designed to prevent wherever possible. Armoring incurs a permanent cost by replacing existing coastal processes with a human management burden. This cost should be considered alongside the value of existing at-risk development, and certainly when considering the potential value of future development.

¹⁵ EGLE, “Coastal Wetlands: Essential to the Health of the Great Lakes.” State of the Great Lakes Report pages 20-21, 2021.   https://www.michigan.gov/egle/-/media/Project/Websites/egle/Documents/Reports/OGL/State-of-the-Great-Lakes/Report-2021.pdf. Retrieved April 2025.

¹⁶ EGLE, “What are wetlands and why are they important?” https://www.michigan.gov/egle/about/organization/water-resources/wetlands/what-are-wetlands-and-why-are-they-important. Retrieved April 2025

¹⁷ EGLE, “Introduction to Wetlands” video. https://youtu.be/bSfF6h7j1YU?si=Mhzpbp851RnvUCGD. Retrieved April 2025

¹⁸ NOAA Ocean Service, “What are nature-based solutions?” https://oceanservice.noaa.gov/facts/nature-based.html Retrieved March 25, 2025

¹⁹ NOAA Office for Coastal Management Digital Coast, “Green Infrastructure Effectiveness Database.” https://coast.noaa.gov/gisearch/#/ Updated March 17, 2025; retrieved March 25, 2025

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