Recently I returned to the York Mills area having attended high school in this area. As I exited the TTC station, it dawned on me how much this area (Hoggs Hollow) is shaped by the distinct geomorphology of the region. ... so... why not create an Earth cache?
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NOT A NIGHT CACHE.
In order to successfully complete this EC, please read the whole lesson and take careful observations of your surroundings. This is a D3.5 EC, so allow sufficient time to read, observe, reflect and respond. To be clear, one word responses are insufficient to answer the questions, and answers need to reflect both what you've read in the lesson and what you observe at GZ.
Any finds that appear to reflect "arm chair" answers (or those that are incomplete/missing answers) will be removed. The point of an EC is to visit the site in person, and demostrate that you've learned something about the local geology/geography.
Please send your responses via the in-game IM system. I will read and reply to all responses.
If working as a team, each person must post their own photo when logging a find, and the caching names of participants must be included by the person who is submitting the answers.
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Questions:
1. Post a photo of you/your GPS/your caching name with the YORK MILLS STATION sign.
2. Based on the cache lesson and your observations of GZ, describe how geological processes influenced the formation of Hoggs Hollow at York Mills and Yonge Streets. Be particularly mindful of comparing and contrasting the origins of the Don River Valley and its present condition.
3. After reading the lesson, and based on your observations of the natural surroundings at GZ, describe (in your own words), the interrelationship between the soil type and Don River in this area.
4. Based on the cache lesson, and your observations of GZ, explain why this area would be susceptible to the effects of natural disasters like flooding due to storms or hurricanes like Hurricane Hazel.
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Hoggs Hollow is a residential neighbourhood in Toronto, Ontario, Canada. It is located in the Don River Valley and centred on the intersection of Yonge Street, York Mills Road, and Wilson Avenue. Historically, this area was the site for grist mills and whiskey distilleries (sorry - those are now gone).
Don River Valley
The Don River is a watercourse in southern Ontario that empties into Lake Ontario, at Toronto Harbour. The Don is one of the major watercourses draining Toronto (along with the Humber, and Rouge Rivers) that have headwaters in the Oak Ridges Moraine.
The Don is formed from two rivers, the East and West Branches, that meet about 7 kilometres (4 mi) north of Lake Ontario while flowing southward into the lake. The area below the confluence is known as the "lower Don", and the areas above as the "upper Don". The West Branch of the Don flows through this section of Hoggs Hollow.
Geology
The Don Valley is notable because of its deep wide valley in the lower reaches. At the Bloor Street Viaduct, the valley is about 400 m wide while the river is only about 15 m wide. This is due to its glacial origins. The Don River and its deep valley were formed about 12,000 years ago at the end of the Wisconsinan Glaciation. During that glaciation which lasted for 35,000 years, all of Ontario was covered in ice. As the climate warmed the glaciers began to melt. As the ice front retreated in southern Ontario, several rivers were formed that drained into Lake Iroquois, a glacier lake which was the precursor to Lake Ontario.The Don River is now small in comparison to the deep and wide valley that resulted from its glacial origin. The Don River is now classified as an underfit river.
A misfit stream is a river that is either too large or too small to have eroded the valley or cave passage in which it flows. This term is also used for a stream or river with meanders that obviously are not proportional in size to the meanders of the valley or meander scars cut into its valley walls. If the misfit stream is too large for either its valley or meanders, it is known as an overfit stream. If the misfit stream is too small for either its valley or meanders, it is known as an underfit stream (or river).
The term misfit stream is often incorrectly used as a synonym for an underfit stream. An underfit stream is a type of misfit stream whose discharge is too small to be correlated with either existing channel characteristics, i.e. meander radius, wavelength and channel width, or valley size
The landscape at that time was loose glacial till so the large amounts of glacier melt water eroded deep valleys over thousands of years. As time progressed, isostatic uplift caused the earth's plate to rise and tilt. This caused Lake Iroquois to drain towards the south.
The location of the old shoreline delineates a change in the soils in the Don watershed. Soils north of the old shoreline are mostly luvisolic Halton Till while south of the shoreline they are sandy glaciolacustrine deposits. Hoggs Hollow is located north of the old shoreline (roughly Eglinton Ave). Luvisolic soils are forest soils that form in medium- and fine-textured parent materials. Luvisols have a coarser-textured surface mineral horizon overlying a finer-textured mineral horizon that is higher in clay than the overlying horizon. Luvisols are widely used for agriculture.
Hydrology
Due to the urbanized nature of the watershed, the Don River experiences low base flows interspersed with high volume floods. The water level can rise very quickly following a moderate to heavy rainfall, up to 1–2 metres inside of three hours. The average base flow for the Don River is about 4 m3/s. Peak flows occur in late February and late September which corresponds to seasonal variation in the Toronto region. Maximum flows, based on a Hurricane Hazel level flood have been estimated at nearly 1700 m3/s. On August 19, 2005, an unusually strong summer storm caused short term flooding in the Don Valley. Peak flow rates for that event were measured at 55.3 m3/s. Since high flow rates occur during storm events, the resulting floods tend to scour the bottom of the river which reduces fish habitat. In addition, the flood waters carry a large amount of sediment washed into the river from surrounding tablelands. The sediment collects in the Keating Channel just past the mouth of the river (this is at the shore of Lake Ontario and (significantly) south of Hoggs Hollow). The TRCA which is responsible for the dredging estimates that the amount of sediment dredged is 35,000 m3/year weighing nearly 60,000 tonnes (59,000 long tons; 66,000 short tons)
Environmental Impacts and Human Reaction
In the 1880s, sewers were laid through ravines in the Don Valley to carry sewage, offal and industrial effluents. Pollution and foul odours continued until the late 1950s. Since then, small improvements have been made. The city installed waste water storage tanks, required homeowners to disconnect downspouts, and swept streets for contaminants that flowed into waterways. Since 1979, the Lower Don has shown improvements in dissolved oxygen, phosphates and suspended solids; however by 2021, the tributary Taylor-Massey Creek had shown little improvement. This tributary is about 10 km southeast of Hoggs Hollow.
Increasing development in the Don River Valley throughout the 1950s, including to the east of Hoggs Hollow, reduced the natural areas of the watershed. This impacted the Don with increased pollution, heavy flooding, and turbid sediment laden waters. The combined result meant that by the 1960s the river was a neglected, polluted mess. In 1969, Pollution Probe held a much celebrated "Funeral for the Don" to highlight the plight of the river. Throughout the 1960s and into the early 2000s, various groups worked together to "Bring Back the Don".
As of 2021, the Don River still suffers from sewage pollution during heavy rainfalls, when storm sewers carrying both rain water and sewage overflow into the Don River and its tributaries. To remedy this problem, the city is spending $3 billion to build three tunnels totaling 22 kilometres (14 mi) in length to divert sewage away from the river and redirect it to the Ashbridges Bay Treatment Plant. The project began in 2018 with an expected completion in 2038 of all three tunnels plus five storm water storage shafts. As of 2021, a tunnel boring machine has completed roughly half of the 10.4-kilometre (6.5 mi) Coxwell Bypass tunnel located 50 metres (160 ft) underground alongside the Lower Don south of the Leaside Bridge. These tunnels are located about 10 km southeast of Hoggs Hollow.
On October 15, 1954, the valley was inundated by Hurricane Hazel, and many attempts have since been made to manage water in the natural watershed of a valley, though many homes are still prone to moisture and flooding from the water table. A steel truss bridge carrying Yonge Street across the river was damaged and temporarily replaced by a Bailey bridge until a new bridge was built. In 2001 an environmental assessment was started to look into a natural mouth of the Don. The project was also coupled with a plan to handle a major flood modeled on the expected output from a Hurricane Hazel size storm.
Not so Fun Fact
On March 17, 1960, the incident popularly known as the "Hoggs Hollow Disaster" occurred. Five young Italian immigrant workers were killed while constructing a tunnel for a water main at Hoggs' Hollow. The details of the accident, where they were trapped 35 feet underground in a cramped, dimly lit tunnel, sparked a public outcry over the lack of safety standards in construction. Ultimately, the outcry led to an improvement in working conditions, such as the passing of the Industrial Safety Act.
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Questions:
1. Post a photo of you/your GPS/your caching name with the YORK MILLS STATION sign.
2. Based on the cache lesson and your observations of GZ, describe how geological processes influenced the formation of Hoggs Hollow at York Mills and Yonge Streets. Be particularly mindful of comparing and contrasting the origins of the Don River Valley and its present condition.
3. After reading the lesson, and based on your observations of the natural surroundings at GZ, describe (in your own words), the interrelationship between the soil type and Don River in this area.
4. Based on the cache lesson, and your observations of GZ, explain why this area would be susceptible to the effects of natural disasters like flooding due to storms or hurricanes like Hurricane Hazel?
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About SideTracked Caches
This cache belongs to the SideTracked series. It is not designed to take you to a magical place with a breath taking view. It's a distraction for the weary traveller, but anyone else can go and find it too.