The history of the Odoonabii-ziibi ( Ojibway) or Otonabee River started with the melting of the Wisconsin ice sheet which generated large quantities of water that drained along a number of spillways to Lake Iroquois, the present-day Lake Ontario. The source of the Otonabee River is Katchewanooka Lake at the north end of the community of Lakefield. There are a 10 smaller tributaries that also feed into the Otonabee River including Squirrel Creek, Baxter Creek and Caven Creek, names familiar to local geocachers for the paddle caches along the river and side creeks.
River Island
A River Island is an exposed landmass surrounded by river water, excluding shoals between seasonally varying flows and excludes semi coastal Islands in river deltas. These Islands result from changes in the course of a river and may appear as vegetation free shoals, or mudflats which can dissipate or shift depending on water levels as well as sediment build up which will grow in size with either artificial reinforcement or more likely natural factors including build up of plants, grass, shrubs and trees which root the soil in place and protect the shoreline from further erosion.
Some key processes in the formation of an river island formation include:
Erosion and deposition: A river erodes material (like sand and gravel) from one area and carries it downstream to deposit it in another. These depositional zones can grow into islands over time.
Changes in river course: As a river's path changes, a new, smaller channel may form, leaving a strip of land in the middle that can become an island. This can happen as a result of interactions with tributaries or other fluvial actions.
Natural obstacles: The accumulation of material can be triggered or accelerated by obstacles in the river, such as a log jam, a natural obstruction, or even a small rock formation. These obstacles slow down the water, causing it to drop sediment.
Vegetation: Once a small mound of sediment forms, plants can begin to grow on it. This vegetation helps to stabilize the land and trap even more sediment, leading to the island's growth and permanence.
Avulsion: This is a more sudden process where a flood or other event causes the river to change its course dramatically, separating a piece of land to form an island.
High-energy events: Extreme events like major floods can both create and destroy river islands by rearranging large amounts of sediment.
Fluvial Action
Fluvial action shapes rivers and streams through erosion, transportation and deposition.
Erosion can wear away the land through
- Hydraulic action where the force of water and pressure break away pieces of the bank
- Abrasion scouring action with sediment particles carried in the water grind the riverbank and riverbed
- Corrosion is a chemical wreathing process where slightly acidic water dissolves rocks on the riverbed such as limestone or chalk
- Attrition is the wearing down of rocks and pebbles as they collide when transported in the river
Transportation is the movement of eroded material downstream
- In Solution where dissolved material is carried in the water
- In suspension where finer particules like silt and clay are carried in the water flow
- By saltation where heavier particles like sand and gravel “hop” or bounce along the bottom of the riverbed
- And as bed load where large rocks and stones are rolled or pushed along the bottom
Deposition is the dropping of sediment where the river’s energy decreases, often found at the mouth of a river or when the river or floodplain.
Flooding
The Otonabee has witnessed a number of major flooding events over the years due to high water levels from snowmelt, heavy rainfall , storm events and infrastructure problems resulting from undersized culverts and bridges. A major flood occurred in 2014 which resulted in 95 million in insured losses in Peterborough which resulted in extensive damage to infrastructure and more recent flooding events in spring 2024 which resulted in road closures due to high water levels and flows, and July 2024 from a widespread rainfall event. More recently in April 2025, flooding occurred in low-lying areas with potential risk of building flooding, basement flooding and road closures.
This earthcache is located mid channel on the Odoonabii-ziibi or Otonabee River and will require a water craft to get to the posted coordinates.
Please send me your answers using the messenger 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.
Questions
- Based on your observations and the description in the write-up, what key processes do you believe played a roll in the formation of the island? Include all processes you believe played a role if more than one.
- Looking at the “ Island”, do you believe it is well established in the river or could sediment deposition fill the channel between the land and Island?
- Visit the posted coordinate and observe the flow of the current. You can use a leaf or twig to make your observation. Next visit the second waypoint and make the same observations. Do you notice a difference in the current between the main channel and secondary channel? Which one shows a faster current?
- Mandatory: Take a photo showing the Island in the background from the posted coordinates and upload it to your found log.
References
https://www.trentu.ca/natureareas/sites/trentu.ca.natureareas/files/documents/TNA%20Geological%20History_0.pdf
Draft-The Stewardship Plan for Trent University Nature Areas
AI Overview was referenced for Key formation processes and definitions.
