Erosion – climate change and city growth
The effect of storms
The total drainage area into Yellow Creek in the Vale of Avoca ravine is about ten square kilometres, the area draining into Mud Creek roughly one-third that large. Every time there is a significant rainstorm, all the water that falls on those two areas rushes down into the two creeks. A similar volume of water drains into the Park Drive Reservation ravine through a large pipe from Cedarvale Ravine.
We get several rainstorms each year in which more than 20mm of water per hour falls on the two drainage areas. Each time that happens, the stormwater flood quickly reaches a flow rate of more than 60 cubic metres every second. That’s the equivalent of 60 metric tons of water blasting into the walls and bed of the stream every second. When that persists over an hour, that deluge adds up to a total of over 200,000 metric tons of water scouring the Yellow Creek channel, even more in a major multi-hour storm. It should be no surprise that erosion is the most serious issue that must be dealt with in planning for the two ravines.
Climate change is a killer — of ravines as well as people. Toronto has experienced three ‘once in a century’ storms just in the past 17 years. So much for traditional metrics.
Invasives and stewardship
MRG works with Toronto Nature Stewards to promote citizen stewardship of the ravines.
We are keen to promote stewardship initiatives. Stewardships are an important element of the City’s ravine strategy — the City does not fund enough maintenance work to keep invasive species under control without help. We believe neighbourhood residents can and want to participate in the work. The need for stewardship is so much larger than what the City can accomplish within its financial resources. And the need is great. Many citizens would welcome being able to play a more important role.
The City’s parks operations are seriously underfunded. The ravines throughout the city are an important resource that is being allowed to deteriorate because of underfunding, both through erosion and through the proliferation of invasive species. Stewardship will not deal with the former — we need to fundraise to make progress on that — but it can be of inestimable value in dealing with the latter
We need community involvement in stewardship — you can help!