By Jeff Stone: Department of Geography, University of Wisconsin - Madison

This visualization shows what the hundred-foot high bluffs in Ozaukee county, north of Milwaukee would have looked like in 1956.

This visualization shows the Ozaukee county bluffs in 2000 after they have retreated over 100 feet in only 44 years of measurement.

The shoreline bluffs of Lake Michigan are constantly receding, pounded continuously by the relentless waves of the storms of the Great Lakes. In Ozaukee county, north of Milwaukee, the tops of the hundred-foot high bluffs of the western shores have retreated over 100 feet in only 44 years of measurement.

Devouring property and encroaching on existing structures, this inevitable force is steadily changing the face of the coastal landscape, demanding adaptation and response from local stakeholders. Though dramatic in geological time, this dynamic sequence of change is hard to see in action at a daily glance. Like a hungry animal sneaking in the back door, any solution first requires shining a bright light on the problem to mobilize support for the endeavor. At University of Wisconsin Madison, Steve Ventura, David Hart, Alberto Vargas and Jeffrey Stone developed a visualization to relate bluff erosion understanding to the public. Utilizing ERSI ArcGIS products with 3D Nature?EUR??,,????'???s Visual Nature Studio, a time-accelerated animation demonstrates clearly the phenomenon and the risks associated with it.

The study area focuses on an approximately 1000ft long stretch of shoreline just south of Concordia University, where long-term monitoring provides adequate data to reconstruct landscape morphology in the period of 1956 to 2000. Historical and current orthophotos were used to capture bluff top and bottom (toe) isolines to track bluff progression. The Land Information and Computer Graphics Facility at UW Madison developed an interactive Flash website www.geography.wisc.edu/coastal/viz3d/) to present their findings to the public.

The interface of the ERSI ArcGIS products with 3D Nature?EUR??,,????'???s Visual Nature Studio: a time-accelerated animation illustrating bluff erosion and mitigation.

Causes of Bluff Erosion

Bluff erosion is driven by a host of factors including wave and lake level action, runoff and groundwater, freeze and thaw cycles, lake ice abrasion, and even wind. Years and even decades can pass without any major change, followed by sudden slumps where sections 100 feet wide and 50 feet deep can fall into the lake. The glacial till medium decreases in stability as it gets steeper, as it has since 1956, eroding from an original slope of 17 degrees to 24 degrees in the year 2000. These continuous changes cannot be stopped, but can be anticipated, mitigated and accounted for in local planning.

New construction placement should factor in a bluff-top setback margin calculated based on the erosion conditions (bluff height and angle and stability, resulting in a Stable Slope Angle), yearly recession rate and the expected useful life of the structure. A new well-constructed building could have a lifespan of up to 100 years. The toe of the bluff has receded 106 feet in 44 years, almost 2.5 feet a year, which would extrapolate to nearly 241 feet in a century. In this same period, the top of this bluff has only moved 14 feet (31 feet per century) but in some areas it can erode much faster. In this visualization, a minimum bluff-top setback of 75 feet is shown.

Bluff Mitigation

After ensuring that new construction will not succumb to erosion during its expected lifetime, other measures can be considered for mitigating bluff erosion. As of January 2005, Concordia University planned to raise $8 million to perform bluff stabilization on their property. While ?EUR??,,????'??hard armoring?EUR??,,????'?? of beaches with durable materials like cement or boulders can deflect scouring energy and decrease wave-driven erosion, these approaches are no longer in vogue. Some erosion is desirable to replenish sediment into the beach ecosystem cycle, denying this source at one location can have adverse effects on beach vitality at down-current sites. Wisconsin?EUR??,,????'???s Great Lakes coastline is already starved for sand, especially south of Milwaukee where infrastructure protection armoring has caused a coastal arms-race in pursuit of ever-depleting sand.

The new best-practice for bluff stabilization recommends situational analysis followed by targeted problem solving. The best way to deal with erosional conflict is to avoid it altogether by not building new structures where they will be harmed by it. Nature has steadily eroded the Lake Michigan coastline many miles over the last 10,000 years, and in the end will not be denied its due.

However, the inevitable may be slowed by careful determination and mitigation of the actual causes. Poor stormwater management from hardscape surfaces, as well as groundwater and seepage from permeable areas can all accelerate bluff degradation. Fortunately, these factors can be managed with proper planning.

Researchers at the University of Wisconsin, Madison track the changes of the bluffs on the western shores of Lake Michigan. They are stabilizing the area through situational analysis and targeted problem solving.

Stabilizing for the Future

One of the easiest and most effective tactics for slowing erosion is the planting of vegetation. The natural cycle of vegetation growth can be augmented by a landscape design featuring durable species suited to the environment, planted at a growth stage where they can successfully stabilize the soils. Synthetic ?EUR??,,????'??soft?EUR??,,????'?? erosion prevention measures and materials can also be beneficial, especially during the early vegetation establishment phase.

Finally, where constraints dictate more aggressive protection (irreplaceable buildings, cultural assets or critical infrastructure), more drastic measures like hard armoring can be judiciously employed. The disruptive side-effects of these constructs can somewhat be offset by gentler measures elsewhere as appropriate.

Bluff erosion is an inescapable reality, a force of nature to be reckoned with, and only a small facet of the tremendous forces that have sculpted the shape of the Earth into the landforms that are its recognizable face of today. To presume to halt these processes is folly and non-productive. In human lifetimes however, they can have an undesirable impact on cultural and infrastructural assets along the Lake Michigan shoreline. By using animation technologies to assimilate and integrate data gathered over nearly half a century, a visualization can be constructed that concisely depicts these glacial-paced changes. Viewed from this artificially accelerated vantage point, the requirement for and goals of erosion mitigation become crystal clear, leading to stakeholder buy-in and improved planning. Careful landscape design principles can greatly extend the lifetime of the bluffs, the structures behind them and the beaches below them.