Mount Baldy Restoration

Mount Baldy is the largest moving dune along Indiana's coast.

NPS / K. George

Mount Baldy is a 120-foot sand dune at the southern tip of Lake Michigan, lying within the eastern end of Indiana Dunes National Park. The dune began forming some 4,000 years ago and is continually changing as a result of natural factors.

During the last 175 years, anthropogenic (human caused) influences have greatly impacted sand movement at Mount Baldy, causing the dune to move inland at an unnatural and alarmingly fast rate.

In 2013, a small boy disappeared beaneath the surface of the dune. His rescue and the subsequent research that was launched on Mount Baldy unvieled a phenomnenon unknown to the scientific community.

 

Restoration on Mount Baldy utilizes wind blocks and marram grass plantings.

John Kwilosz

Mount Baldy: Mystery and Motion

Mount Baldy, a giant sand dune at the southern tip of Lake Michigan, is constantly changing. As scientsits and resource managers study the geomorphology of this dune, they are uncovering secrets of its past and keys to the management of this dune, both now and in the future.

Mount Baldy, a 120-foot sand dune at the southern tip of Lake Michigan and the eastern end of Indiana Dunes National Park, appears at first glance to be a giant sand dune, plain and simple; yet aspects of Mount Baldy are a source of puzzlement. Researchers and resource managers at Indiana Dunes National Park are investigating many facets of this geologic treasure. As they solve the many mysteries of Mount Baldy, the insights they gain will lead to better protection and restoration of the dune, as well as increased safety for park visitors.

Mount Baldy was beginning to form some 4,000 years ago, along the edge of what geologists call the Tolleston Beach. Mount Baldy formed the same way dunes form today: waves deposit sand grains on the beach, winds blow the sand inland, and the sand keeps moving until either the winds die down or the sand encounters a plant or other obstacle and settles to the ground. More and more sand grains follow suit and a sand dune is born. These young dunes are formed just inland from the beach and are called foredunes. Vegetation plays a key role in the dune formation process. Marram grass (Ammophila brevilgulata) is one of the few plants that can thrive in the dynamic environment of the foredune. This pioneer species can grow quickly, keeping its leaves above the rising surface. New plants develop from the rhizomes, trapping and anchoring more sand. Sand continues to mound up, the grass continues to grow, and the dune grows taller.

 

Mount Baldy as viewed from its western summit.

NPS

Originally, the dune in this location grew to be a parabolic dune, generated by winds out of the west. With time, the dunes became stabilized- covered in forest vegetation that held the sand in place. The dune remained stabilized long enough for soil to develop from the organic material on the forest floor. Then, approximately 820 years ago another dune formed, grew, and advanced inland, burying the older dune. As time crept on, sand from the new dune continued accumulating, covering the forest in its path, and creating the present day Mount Baldy.

Dune sand does not just accumulate, it also erodes. A blowout is a bowl-shaped depression in the dune, caused when a disturbance like human foot traffic removes vegetation and exposes sand to the wind. Wind blows the sand up and over the edge of the depression. As more erosion occurs, the blowout becomes wider, with the down-wind rim of the "bowl" increasing in elevation. Sand blows from the lakeward side of the blowout up and over the rim, and tumbles down the backside, burying anything that might be in its path. A large blowout has formed on Mount Baldy, probably the largest blowout along the southern shore of Lake Michigan. A great deal of sand has been eroded from the blowout, and a dark colored line can now be seen curving across the face of Mount Baldy. At first, the line seemed a mystery, but geologists have identified it as a layer of soil that developed from the decay of organic material on top of the initial dune that formed on the site. This soil is known as a paleosol or fossil soil. Exposed palesols help scientists understand the shape and orientation of earlier sand dunes.

 

Parabolic dunes form from a foredune being shaped by prevailing winds.

NPS

Today, Mount Baldy is a large, compound, and complex parabolic dune. Compound dunes are large dunes on which smaller dunes of similar type are superimposed, and complex dunes are combinations of two or more dune types. The winds have shifted since the earliest dune was formed. Mount Baldy's current orientation indicated it was formed by winds from a predominant north-to-northwest direction. In 2012, the highest elevation on Mount Baldy (718 feet above seal level, 140 feet above the surface of the Lake Michigan) ocurred along the southeast portion of the dune, along the dune's east arm and crest.

 

Mount Baldy area as viewed from above.

NPS

Investigating Shape and Motion
Geological investigations show us that natural processes move and shape sand dunes. Contemporary observations of these processes have led to a better understanding of the complex relationships among wind flow, topography, weather, climate, and vegetation in relation to sand movement and changes in topography.

Lake Michigan levels, precipitation, air and surface water temperature, frequency and intensity of storms, and duration of nearshore shelf ice all influence sand movement at Mount Baldy. Researchers recently analyzed these factors to determine which ones control rates of sand transport and coastal dune movement. The most favorable conditions for sand transport and movement occur when

• Lake Michigan's level is rising and staying above the long term average,
• storms are more frequent,
• precipitation amount and duration of shelf ice are below average, and
• air and surface water temperatures are above average.

When researchers analyzed each of these factors separately, they found that the order from most to least significant factors in sand transport and coastal dune migration is:

• frequency and intensity of storms,
• rising Lake Michigan level,
• warmer than average air and lake surface water temperatures
• shorter than average duration of nearshore shelf ice, and
• lower than average precipitation

 

Lines showing the position of Mount Baldy's southern edge migrating over time.

NPS

Mount Baldy is commonly referred to as a "living dune", a term that reflects the rapid south/southeastern migration of the landform during roughly the past 50 years. A study of aerial photographs revealed that from 1938 to 2008 Mount Baldy advanced inland 443 feet toward the south, at an average rate of 6.23 feet/year. The highest rates of the dune's movement (10.83 feet/year) ocurred from 1965-1973. Staff at Indiana Dunes National Park plan to remove the restrooms and other infrastructure as the dune continues its march toward U.S. Highway 12. Mount Baldy's rate of movement is significantly faster than other "living" or moving dunes on Lake Michigan. Why is this true?

 

Human-caused Changes Along the Shoreline
In a more natural state, sand would move down the Lake Michigan shoreline from the east, settling, at least temporarily, on the beach at the foot of Mount Baldy. Some of that sand would blow from the beach up into the dune and be captured and held in place by plants like marram grass, causing the dune to grow. Today much less sand actually makes it to the beach at Mount Baldy. Beginning in 1836, piers, breakwaters, and other shoreline structures were constructed at the Michigan City Harbor, just east of Mount Baldy. Sediments in the lake moving from east toward Mount Baldy, become trapped by these man-made shoreline structures before ever reaching the beach at the foot of the giant dune. The structures almost completely blocked the sediment supply to Mount Baldy and initiated an ongoing cycle of sediment starvation and coastal erosion. From 1834 to 1923, Michigan City's Washington Park (just east if the harbor structures) accumulated more sand, extending its beach into the water at an average rate of 7.5 feet/year. West of the harbor structures, near Mount Baldy, the beach property was disappearing with the shoreline receding at an average rate of 9.5 feet/year from 1907-1946. The deficit of sand one the Mount Baldy beach allows high waves to erode away the existing foredune, and its sand is swept out into the lake.

More recently, Mount Baldy became a popular destination site for Indiana Dunes National Lakeshore visitors. Over 92,000 people visited the dune in 2012 alone. Decades of recreational use have taken their toll. Few plants exist on the face of the dune because these plants are sensitive to trampling. When the wind blows, the sand is picked up and blown off the dune because there is little vegetation to hold it in place. The sand fueling Mount Baldy's migration is coming not from the beach, where erosion has left little to spare, but from the middle of its lakeward slope instead. In the words of Erin Argilyan, a geologist at Indiana University Northwest, "The dune is flattening."

 

Golden sunshine reflects on Lake Michigan.

NPS

Unlocking the Secrets of Restoration
Staff at Indiana Dunes National Park are charged with protecting the natural resources in the park to insure they are unimpaired for future generations. Resource managers actively manage and mitigate the negative impacts of shoreline development, visitor traffic, and habitat degradation. National park employees take this job very seriously and have initiated several projects to slow the migration of Mount Baldy to a more natural rate. They have enlisted the Army Corps of Engineers to periodically transport additional sand to the beach just east of Mount Baldy (but west of the Michigan City Harbor). This "beach nourishment" partially offsets the deficit of sand created by the harbor structures and eventually works its way to the foot of Mount Baldy, temporarily providing a source of sand for the dune and helping minimize erosion.

Beach nourishment has helped, but it is not enough. In 2011 the National Park Service at Indiana Dunes National Lakeshore declared the dune an "impaired" landform and began actively working to restore the dune and slow its landward migration through several means including restricting visitor access, continued beach nourishment, re-vegetation efforts, and installing wind breaks.

 

Junction for Baldy's Summit Trail with signage indicating its closure to the public.

NPS / K. Swift

Trails were strategically rerouted and even closed. Visitor access was restricted in areas to prevent the dune and dune vegetation from being trampled. Signs were installed to educate people and remind them to stay on the designated trail. Park staff and volunteers spent countless hours planting marram grass to hold the sand in place. Interpretive rangers were stationed on site to talk with the public about the situation. These efforts have helped, but how much? How can we measure their effectiveness?

The capacity to preserve, manage, or restore highly dynamic coastal landforms requires a thorough understanding of their evolution and the ability to monitor short term landscape change. Monitoring initiatives are currently in place on Mount Baldy: the Northwest Indiana Restoration Monitoring Inventory has established vegetation plots to track changes in plant densities and species composition, and photographic monitoring stations have been established by park managers to visually record changes to the dune.

A research project established additional strategies and methods for monitoring both dune morphology and wind flow to assess both short and long-term restoration success on coastal dunes. The project utilized LiDAR (Light Detection and Ranging), a remote sensing method used to examine the surface of the Earth. LiDAR data from 2010 was provided by Porter County, Indiana, and used to create a digital terrain model that will serve as baseline data for evaluating ongoing changes in the Mount Baldy landform. Additionally, a permanent surveying grid was established with 5 transects running north-south and 5 transects running east-west across the lakeward slope. Utilizing ground surveying techniques, individuals recorded elevation data every 25 feet along each transect, also recording any notable variations in topography between points. This data was used to develop digital terrain models for 2012 and 2013. This permanent surveying grid allows for the long-term comparison of ten topographic profiles across the dune's lakeward slope, and may show how planted areas have served to stabilize the dune.

 

Direct comparison of the 2011, 2012, and 2013 models identifies and quantifies areas of erosion across the dune form. Investigators interpret the results:

In general the north-south transects illustrate the following trends:

• Erosion of the stoss (lakeward) slope; erosion is evident at all sites at an elevation above 620ft above sea level and is greatest at elevations above 650ft.
• The base of the lee side of Mount Baldy migrated approximately 44.5ft between 2010 and 2013.

In general the east-west transects illustrate the following trends:

• Development of the foredune: both erosion and deposition occur in the area of the foredune (<620ft), with accumulation ocurring in the center of the dune. The National Park Service has focused restoration efforts in this area by planting marram grass in 2011-2014. While erosion dominated from 2010 to 2012, the area appeared to generally stabilize from 2012 to 2013.

Utilizing this dune monitoring system will have many advantages for resource managers: (1) it is a method of quickly assessing short-term changes in dune morphology through time, (2) the north-south profiles quantify dune migration through shifts in the position and elevation of the crest and/or basal slipface, (3) the east-west transects allow for tracking of changes in erosion and deposition across the lakeward slope which is the intended area of restoration on Mount Baldy.

Another component of the same study utilized a portable wind-profiling station consisting of paired wind vanes and anemometers at various heights above the ground. Wind data including wind speed and average wind direction were collected at 5-minute intervals. Wind data can be generated to guide the design of wind-block construction as a part of the restoration efforts on Mount Baldy. This is of particular interest to resource managers who are experimenting with a variety of different materials to slow the wind in order to prevent it from eroding sand from the face of the dune and to protect newly planted marram grass while it develops extensive root systems. In 2014, rows of discarded Christmas trees, logs, snow fencing, and cut shrubs were strategically installed and are being monitored to determine which will prove the most effective at stopping the transport of sand and rebuilding areas of the dune. (Logs and branches were collected from invasive species removal and habitat improvement projects in nearby areas of the park.) Efforts will continue to monitor the impacts of these wind blocks on wind speed, and on dune building.

A third component of the study sampled surface sediments across the face of Mount Baldy and established patterns in grain-size distribution and transport. Resulting data shed light on the potential fate of nourished sediments of different sizes at they move from the beach up and across the dune. Results show that sediment in the range of fine sand or smaller will be eroded from the dune and will not contribute to dune buildings. The results of this sediment analysis will help inform managers as they formulate beach nourishment plans that consider both the aquatic and terrestrial (dune) environments.

 

Filled in decomposition chimney on Mount Baldy's surface.

NPS

The Biggest Mystery of All
On the afternoon of July 12, LaPorte County 911 and the park dispatch center received simultaneous calls reporting that a child had fallen into a hole near the top of Mt. Baldy. National Park Service (NPS), employees, who were already at Mount Baldy on a dune restoration project, were the first responders. They called the park’s dispatch office and began rescue efforts. Within 15 minutes units from the Michigan City Police and Fire Departments arrived and were closed followed by NPS Rangers.

The first officer on scene saw a group of people, including the child’s family, frantically digging into the north side of the dune, about midway between the beach and summit. They told the officer that a six-year-old boy had fallen into a cylindrical hole and disappeared into the dune. The seven-year-old brother of the victim said the boys found the hole in the sand and wanted to see how deep it went. The younger brother disappeared below the surface after he climbed into the hole with the intent of standing in the bottom. The victim’s father said that he could hear his son crying for help, but could not see him. As the family members attempted to dig the boy out by hand, the hole collapsed and filled with sand.

As emergency personnel arrived, a joint operation between NPS and City agencies was initiated and digging continued with hands and shovels. One-hour of continuous work resulted in a hole that was approximately 30-feet wide and eight-feet deep, with still no sign of the boy. High heat and collapsing sand hampered the rescue effort. While hand work continued, local contractors (D & M Excavating, McRuff and Sons) and a local utility (Northern Indiana Public Service Company) were called in to use heavy equipment to assist in the digging. At the peak, approximately 50 rescuers from the NPS and cooperating agencies, along with two excavators and a backhoe were working on site. Almost 3.5 hours after the initial call, and after approximately 200 cubic yards of sand were removed from the site, the non-responsive boy was located at a depth of 11 feet beneath the surface of Mount Baldy. The boy was found inside what may have been a decayed root ball from a long-buried tree.

The boy was placed in the care of the Laporte County EMS. Enroute to the hospital, the boy spontaneously regained vital signs. He was airlifted to Comer Children’s Hospital of Chicago and made a full recovery. Evidence at the scene supports that theory that the boy encountered the remains of a tree buried long ago by the advancing dune. As the tree decayed, it left behind a shell of compacted sand and bark remnants. The erosion of the dune exposed the trunk of the tree. The boy possibly slid down the void left by the decaying trunk.

 

Small decomposition chimney on Mount Baldy.

Erin Argilyan

Following the accident, the entire dune face, the beach, trails, and parking lot were closed for public safety. An understanding of what lies under the surface of the sand will help park managers prevent a similar accident from happening in the future. Following the accident, the United States Environmental Protection Agency conducted a study establishing that ground penetrating radar (GPR) is a viable tool to image the underlying layers of the dune. The technique was capable of imaging to a depth of approximately 30 feet and recognizing a buried soil horizon that was an exposed part of the dune in the middle of the 20th century.

The study also plotted known depressions/holes, and these features appear to align themselves with the relict, buried southeastern sloping slip face of the dune that was similarly exposed in the mid-20th century. Over 66 "anomalies" or irregularities under the surface have been identified. Erin Argilyan's research confirmed for the first time in scientific literature that these anomalies are the result of buried trees decomposing into hollowed chimneys underneath the sand (Argilyan et al., 2015). Since the accident, at least six additional holes have appeared on the surface of the dune. They were short-lived, generally filling in with sand within hours of being discovered.

 

Rangers explain Mount Baldy's movement while on tour atop the dune.

NPS

Efforts to stabilize the dune appear to be working. Plantings are still intact, wind breaks are slowing sand movement, and some plants have even colonized portions of the dune, becoming established on their own. On Baldy's lakeside slope, vegetation has a stronger hold at lower levels than the top. The dune has flattened and lost height as the loose sand on top keeps blowing backward.

Mount Baldy's summit is currently closed to the public, only available during ranger-led tours where visitors are brought to safe locations. This time without major foot traffic will help Mount Baldy recover.