Lake Michigan is Chicago’s wilderness area. Promontory Point was designed and built to be a spectacular encounter for residents with that natural wilderness. (The Point peninsula was built in 1922-1937 along a shoreline lapping S. South Shore Drive.) With climate change over the past decades, we’ve seen these encounters with nature become more dramatic and destructive: wild fires, temperature extremes, drought and storm action. Climate change is man-made too. The Point cannot be exempt from these wilderness forces.
Alfred Caldwell, designer and architect of Promontory Point, chose limestone blocks for the Point’s revetment because it is the native bedrock and because it erodes slowly but persistently. The Point’s armor stones of limestone absorb wave energy constantly. The limestone revetment by design takes the brunt of the storm waves and protects parkland for residents. Erosion is inevitable but it still functions after 83 years.
Caption: rock, rubble debris thrown up onto parkland by wave action in a storm 24-25 October at Promontory Point. By Sunday, 31 October, the Conservancy work group had removed all this debris back into the revetment and reclaimed the parkland for Point lovers' use.
The City’s concrete and steel revetment along the rest of Chicago’s lakefront too takes wear from wave action. Overtopping waves erode adjoining parkland and, in some places, the concrete is already broken and repaired at its half life. Damage to the City's concrete revetment appears on the South Side and Northside (https://twitter.com/michellestenzel/status/1453544930895409152?s=21). In some places it is patched and in others requires replacement. And this erosion damage is already happening at the concrete revetment's mid-life, not quite twenty years old.
Caption: parkland erosion at 53st Street concrete revetment
Poor and minimal maintenance of the Point's limestone revetment over its 83 year history shows the relentless force of Lake Michigan on the structure underpinning the limestone revetment. The Park District did not put geo cloth erosion control around the crib structure holding the limestone in the 1990s-2000s when lake levels were low and the wooden supports exposed to air decay. This geo cloth would now be deterring erosion of the revetment substantially while water levels are high. And the Park District has not put the anti-erosion materials in the parkland seen elsewhere along the lakefront. These materials minimize the scouring power of overtopping waves on the park. Obviously, jute is more organic than plastic webbing. But any assistance and maintenance at the Point would have helped with parkland and revetment erosion over time.
Promontory Point Conservancy advocates for the repair and rehabilitation of the limestone revetment at Promontory Point because it weathers well whether Lake Michigan is high or low. Obviously, the Point needs repair but the success of the limestone, its durability and need for minimal maintenance, over time show it a superior choice to the concrete and steel seen on the rest of the City’s lakefront.