Wilmot and Foster Creek
The Oak Ridges Moraine is the prominent geological landform in the Wilmot Creek watershed, separating the streams flowing into Lake Ontario from those flowing into Georgian Bay, Lake Simcoe and the Trent River. Beginning on the moraine, the headwaters of Wilmot Creek flow south over the Halton Till and Newmarket Till Plains, and over glacial deposits left from the Lake Iroquois shoreline and Lake Iroquois Plain before emptying into Lake Ontario. The diverse physiography in the watershed allows for cold-water and cool-water habitats in Wilmot Creek and its tributaries and warm water habitat in Foster Creek and the lower reaches of Wilmot Creek.
Stream Order
Ordering streams is based on the method developed by Strahler (1964) and is commonly used for grouping watercourses based on similar characteristics, for example stream size and flow. Based on this method, single, unbranched tributaries are classified as first order streams. A second order stream starts at a confluence of two first order streams and ends at its confluence with another second order stream, forming a third order stream and so on. Smaller streams entering a higher-ordered stream do not change its order number.
With increasing stream order comes increasing stream size, flow, habitat complexity, instream productivity and fish species diversity. Typically, first to third order streams are headwaters with high gradient and erosion potential. Forth to sixth order streams are wider with riffle and pool areas, greater depositional substrate like sand, and the power to move large woody material. Within the Wilmot Creek watershed there are 90 streams of the first order, 22 streams of the second order, 6 streams of the third order, 2 streams of the fourth order and 1 stream of the fifth order.
Stream Slope
Stream slope is a major factor in controlling stream morphology including the rate of erosion and deposition of substrate in a watercourse. Watercourses with steep slopes are typically straighter with high velocities and erosion potential then those with low slopes. The resulting habitat characteristics in these streams are higher ratios of riffles and larger substrate like cobbles and boulders in reaches with high slopes and high ratios of pools and fine substrates like sands and silts in those with low slopes.
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Slope %
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Characteristics
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Substrate
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0.0 – 0.3
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Typically sinuous; greater pool to riffle ratio
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Sands and silts
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0.3-1.0
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Relatively sinuous; more or less even pool – riffle ratio
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Gravels and cobbles
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1.0-5.0
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Riffles out number pools; higher water velocities; less sinuous
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Large gravels, cobbles and boulders
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>5.0
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Riffles predominate; water velocities and erosional forces high; typically straight stream channel
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Boulders, cobble and hard clay
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Note: A riffle is a short, relatively shallow and coarse-bedded length of stream over which the stream flows at lower velocity and higher turbulence than it normally does in comparison to a pool. As a result of the lower velocity and heightened turbulence, small ripples are frequently found. Riffles are usually caused by an increase in a stream bed's slope or an obstruction in the water.
Logging requirements:
In order to log this earth cache you will visit two locations along the Wilmot Creek, and Foster Creek, both located within the Samuel Wilmot Nature Area.
Location 1: N43° 54.135 W78° 36.055 (Wilmot Creek)
1. From your observations on the characteristics and substrate at this location, what is the slope percentage at this location?
2. Determine the Volume of Flow (cubic metres per second). To do this measure a 10 meter stretch along the edge of the creek. Find a relatively small floating object like a stick and time how long it takes to travel the 10 meters. If you have a partner, one can stand on the bridge and keep track of the time it takes for the stick to reach the bridge.
3. Using the following equation to determine velocity:
4. Standing on the bridge, determine the average depth of the creek in metres (eg. 40cm = 0.40m.) You can use a length of rope with a weight attached and measure from the waterline to the bottom of the weight.
5. Next approximate the width of the river in metres. You can measure the distance as you cross the bridge.
Multiply the width by the depth to determine the cross-sectional area of the flow in square metres. Next multiply this measure by your velocity to get the Volume of Flow (cubic metres per second).
Location 2: N43° 53.923 W78° 35.825 (Foster Creek)
1. From your observations on the characteristics and substrate at this location, what is the slope percentage at this location?
2. You may use the same equation as above to determine the Volume of Flow (cubic metres per second) or based on your observations, determine which creek has a larger volume of flow?
3. Compare the substrate at both locations. Is it the same or different?
Comparing both streams. Which would you say is the higher ordered stream (where first order is low, and fifth order is highest)?
Submit your answers in an email. Do not post them in your log.
Optional: Pictures are always welcome and can be taken anywhere along either of the two creeks or in Samuel Wilmot Nature Area.