Erosion Risk Management - Bluffers Park
Bulffers Park in Scarborough is a beautiful, multi use recreational park and marina, with public trails, beaches and boating facilities as well as offering spectacular views of the majestic Scarborough Bluffs, a series of high cliffs which are the result of sedimentary deposits from the last ice age formed by wind, water and erosion.
Recently the City of Toronto and Toronto Regional Conservation Area have undertaken a 3 year, large scale construction project designed to reinforce and repair erosion control structures which aid to protect the bluffs and this park for people to enjoy.
First some background about the Southwest Headland
- 1960’s to mid 1970’s, Bluffers Park was built as part of a large lakefilling operation to include armourstone headlands, beaches and revetments as part of an erosion control protection project, to help preserve the sensitive Scarborough Bluffs from wave damage and erosion.
- 2006, TRCA began conducting annual inspections as part of the Erosion Risk Management Program (ERMP).
- In 2010, TRCA commissioned a report which revealed instability of the Bluffers Park headland caused by a combination of toe stability, lack of consistent double layer placement of armourstone in various areas, lack of sufficient filter layering below the primary armourstone, an oversteepened structure slope and wave overtopping.
- Between April 14-15, 2018, a severe wind and ice storm caused extreme wave action in Lake Ontario that resulted in significant damage to the headland and beach, washing large amounts of stone into the lake, onto the park tableland, and scouring the shoreline, causing sections of the rock material to collapse and weakening the headland.
As a result of the report, TRCA and the city of Toronto have undertaken a major beach maintenance project of Bluffers Park South Headland to be conducted in three phases. At this time, Phases I (interim work to provide temporary protection to parkland for winter and spring months), Phases II (Headland), Phase III (southeast beach) are completed and Phase IV ( southwest beach) is in the final stages of completion.
Shoreline Erosion - Natural Causes
There are a number of natural forces that lead to shoreline erosion including wind erosion, frost action, soil creep and slumping, but the most common and powerful source is water. Water erosion can be caused by waves, storms, and changing water levels.
Splash: Precipitation and storm water hit loose soil causing displacement of soil depending on the slope
Waves: caused by boats or natural causes will displace loose soil when the soil composition is loose or natural vegetation has been removed
Ice: Lakes freeze and melt, pushing ice onto the shoreline. Ice can cause significant shoreline damage
Storm water: Storms remove loose soil and layers of soil are removed or displaced causing “Sheet Erosion”
Shoreline Erosion - Human Causes
Humans can cause something called “ accelerated erosion”, which often happens faster than normal erosion and is often harder to reverse. Often humans speed up the natural erosion process by removing vegetation, building structures too close to the shores, or installing seawalls that prevent absorption of wave energy.
Vegetation Removal: Plants that have deep roots create a natural barrier to shoreline erosion by holding soil and sand in place. Destroying this natural barrier to create a grassy lawn is only going to destroy the barrier and accelerate erosion of the shoreline. Aquatic plants also help protect shoreline by absorbing and reducing a wave’s energy so the full force of the wave does not hit the shore.
Seawalls: Many seawalls are constructed from concrete, rock or wood in the hope of controlling erosion of beaches however they often fail when the water level erodes the soil at the bottom or top’s over and erodes the soil on the shoreside of the seawall causing it to fail. Seawalls also create barriers for wildlife which can cause disruption to the entire ecosystem. Seawalls can also mess with your neighbours property with a phenomena called wave flanking, where a wave hits a seawall and is directed sideways instead of downward. The wave is directed to your neighbours property.
Watch Flanking video
Types of Erosion Control measures
To log this EarthCache:
Rules:
1. This earthcache is available during the hours of 7:00am - 11:00pm when Bluffers Park is open. Follow all park rules when visiting
2. All observations can be made from the paved path.
3. Please send me your answers using the messanger feature located on the cache page within 4 days of posting your found log. If there is more than one cacher in your party, include the names in group. Only one person needs to send me the group answers. No spoiler photo's please. Found logs posted without proof you visited the site will be deleted.
Earthcache questions:
1. At the posted coordinates you will find an entrance with stone steps leading down from the paved path to the beach. There is no need to visit the beach for this earthcache. Estimate the height difference from the beach to the paved path?
Do you feel that the steps have been placed far enough back from the water to prevent erosion of the paved trail in a storm or high water event? Give your reason.
2. As you walk from the posted coordinates to the second waypoint, make note of the different erosion control measures that have been put in place. From the cache page, name two different types of erosion control methods in use.
3. From the types of erosion listed on the cache page, which ones, either natural or man-made are the most likely types that affect this location? Now look towards the Scarborough Bluffs and answer the same question.
4. On what dates did a severe ice storm damage the Scarborough Bluffs South Headland in 2018? (Hint: It is on the cache page)
5. Mandatory: Take a photo at a point along the paved path showing you or a personal item with the Scarborough bluffs in the background. Please no spoilter photos showing the erosion control structures
