Effects of Erosion on Bluffs
All of the ravine problems described in the preceding section also impact the bluffs overlooking Lake Michigan, but bluffs are subject to one additional hazard: the action of waves at the bottom of the bluff or "toe".

Large waves are one of the most powerful forces of nature, and therefore, potentially one of the most destructive. A wide beach at the bottom of the bluff is the best protection against wave action, as it dissipates the energy of the waves as they roll up the beach.

Unfortunately, high levels of water and sand loss in the lake have narrowed the beaches so they are no longer able to keep the waves from reaching the toe of the bluff. When the waves do hit the bluff, they scour out the toe of the bluff, gouging into it a line of cliffs, or scarp, which undermine the bluff.

Sooner or later the soil over these scarp will collapse, leaving bare soil which is even more vulnerable to further erosion. Unless the beaches are artificially "nourished" with sand from other sources, or the water returns to very low levels, these problems will only worsen.

High waves are the result of major storms, with winds blowing from the northeast. A "100-year storm"--one with the highest waves recorded, and so named because they occur very seldom--will create gigantic waves which in a few hours can tear out great volumes of soil. Even a "20-year storm," with waves of 15 feet, can wreak enormous damage to the toe of the bluff.

Over many years a protective device called a groin, which consists of a steel bulwark installed at intervals perpendicular to the shoreline, has been used to interrupt the transport of sand. Other protective measures may be more effective.

A wide beach at the bottom of the bluff is the best protection against wave action because it dissipates the energy of the waves as they roll up the beach.

Before buying:

• Inspect the slopes thoroughly. Look for denuded vegetation, slumps and gullies.
• Check the angle of the slopes (whether steep or shallow), and the nearness of structures to the edge of the slope.
• Get advice from a structural or soils engineer familiar with ravines.