Permeable vs Non-Permeable: Why it Matters
In the Toronto area over the past decade, the amount of flooding that has been occurring in urban areas between the Oak Ridges Moraine and Lake Ontario seems to have increased in both frequency and amount. Stretches of the Don Valley Parkway, and the GO train line that runs parallel to it, have been infiltrated by the Don River during high rainfall periods: other areas, such as parts of Downsview, have seen flood water impact from the Humber River. This is despite these rivers having decades-old flood prevention measures in place (in part due to the catastrophic flooding that Hurricane Hazel caused in the mid-1950s).
So, why the increased flooding now? Let's look at the Oak Ridges Moraine:
Credit: Oak Ridges Trail Organization
As this cross-section illustrates, the Oak Ridges Moraine acts as a natural filter, percolating rain water through layers of sand, gravel and clay, then feeding the rivers until they eventually empty into Lake Ontario. Increased development on the moraine has meant an increase in non-permeable surfaces on it--driveways, parking lots, roads, etc.--so that, even with storm ponds implemented, the rain water during heavier rain periods literally runs out of places to go. The result is flooding--at times significant--at the lower elevations within the city of Toronto.
What the Kortright Centre has done with this Living City educational feature is created a practical way to show how the use of differing surfaces on places like parking lots, and the implementation of simple features like rain gardens, can at least alleviate some of the run-off features like this parking lot can create.
What this EarthCache requires:
Around the parking area are a series of information signs as well as an on-site rain garden with signage to show what each element of it is designed to do.
1. Name the two main water sources that run-off from this area will end up in.
2. Describe how the one section of parking lot differs from the rest of the parking lot. If it is raining when you are at this EarthCache, is there a difference in the amount of rain water on the standard parking surface vs the alternative one?
3. What feature in the rain garden filters the water? What other feature breaks down the pollutants?
4. Describe the similarities between the functioning of this rain garden and the functioning of the Oak Ridges Moraine?
5. Measure and include your elevation at the signage for the rain garden.
6. (Optional) include a photo of you with the rain garden behind you.
Please submit these answers either via the Message button at the top or by email. You may log a found-it and then submit your answers, preferably with 48 hours (if you are travelling and it will take longer, please indicate that in your log).
This EarthCache is fully wheelchair accessible (terrain 1). Thank you for enjoying my first placed EarthCache!
This geocache was placed under direct supervision of park staff. Please use the provided trails and visit this geocache only during park hours.
CONGRATULATIONS to DougyB on his EarthCache FTF and4,000th find!