Presentation on theme: "Taylor Creek Park Rehabilitation Project. Taylor Creek Park Rehabilitation In July 2012 a significant storm event caused significant damage in Taylor."— Presentation transcript:
Taylor Creek Park Rehabilitation In July 2012 a significant storm event caused significant damage in Taylor Creek Park including severe damage to three of the main bridge crossings in the park, within approximately a 1 km distance. TRCA in partnership with the City of Toronto, installed a temporary bridge at the location of the Rexleigh Drive crossing in August 2012, to address the immediate requirement to provide safe crossing and connection between the north and south trail in the park, and between the communities. Locations of the three bridges destroyed in the July 2012 storm Temporary Bridge installed in August 2012
Taylor Creek Park Rehabilitation Since 2012 TRCA and the City of Toronto have been working on developing designs, and getting approvals to complete the permanent repairs to the damaged areas, including the replacement of the three bridges, and bank works where storm damage has resulted in risk to the trail. Construction on the first bridge is slated to commence later in 2013, with the remaining works being completed in 2014/15. Location of first bridge to be replacedExample of what the bridge will look like (Wilket Creek)
Erosion Processes and Ravine Property Management
EROSION AND SLOPE INSTABILITY It is important to understand that erosion and slope instability are two different processes, even though they are often associated. Erosion is the gradual loss of soil at the ground surface by water movement, wind, or seepage. While erosion is a natural process, human activities are often a factor in an urban environment. Slope instability consists of a large mass of soil sliding along a planar surface. It is very common for erosion to be a cause of instability, but they are different processes that are assessed as two separate factors. Bank Erosion Slope instability
EROSION PROCESSES The most common erosion processes include: Rainfall and snowmelt cause surface run-off which causes displacement of exposed soil. Sloped surfaces are particularly prone to increased erosion due to increased flow velocity and increased flow concentration. Seepage (springs) and piping affect the strength of non-cohesive soils and cause erosion. Flowing water in a watercourse can cause surface erosion of the bank or channel bed. If the erosion is at the toe of a larger slope, undercutting can trigger slope instability. Wave action along the shoreline of a lake can trigger cycles of erosion and slope instability, which causes recession of the slope crest.
SLOPE INSTABILITY Slope failure or instability involves the sudden movement or sliding of a large mass of soil over a failure (or slip) plane. Slope failures tend to occur more rapidly than erosion processes and often leave a “scarp” at the top of the slope and slumped mass of soil on the ground below. The principle driving force in slope instability is gravity, therefore the steepness of the slope has the greatest effect on stability. Common contributors: Increased slope inclination. Can be caused by toe erosion by water, excavation, construction of un- engineered retaining walls. Un–engineered placement of fill near slope crest and excavation into slope (or retaining walls). Additional loading onto the slope (i.e. impervious materials such as patio stones, structures, pools). Reduced soil strength due to increased groundwater levels, flooding, drying, frost, drainage alterations, or leaks in buried pipes/tanks/pools.
WHAT PROPERTY OWNERS CAN DO Keep yard waste off the slope Yard waste and other debris kills underlying vegetation on the slope and adds unnecessary weight to the upper portion of a slope. Vegetation cover is a primary defense against soil erosion and helps prevent slope slides by helping to reinforce the soil with a root system, remove water from the soil by transpiration, reduce run-off flow velocity, and reduce frost penetration. Encourage growth of vegetation along the top of the slope, and on the slope itself A native vegetative buffer along the top of the slope is encouraged as the root system from the vegetation will help hold the soil together as well as help intercept overland flow draining towards the slope. If a tree is to be removed, leave the tree stump in place If removal of a tree is necessary a permit can be obtain to remove the tree, but leave the stump intact. This allows the root system to remain and minimizes disturbance to the cohesion of the soil. Property owners often unknowingly exacerbate erosion. There are a few simple rules that can be followed to help maintain a ravine property.
WHAT PROPERTY OWNERS CAN DO Divert water runoff aware from the slope face Excessive groundwater and surface water run-off are leading causes of slope erosion. Though we cannot control what mother nature gives us, we can minimize the human contribution to runoff. - Do not over water your lawn and cause saturation of the soil. - Drain swimming pools via a hose that leads to the street. If a swimming pool is leaking, repairs should be made as soon as possible to prevent saturation of the surrounding soil. - Drainage from roofs should be diverted towards the street or all the way to the bottom of the slope if possible. This will help prevent gullies from forming. If draining to the bottom rock should be placed to dissipate outflow and prevent displacement of soil. Hire a professional to stabilize or terrace your slope It is recommended that a geotechnical engineer be hired to design any form of slope stabilization or terracing. Be aware that you will require permit from TRCA prior to commencing such works if: - There is a stream flowing through or adjacent to your property - Your property backs onto a river valley or ravine - Your property backs onto the Lake Ontario Shoreline or a waterfront marsh area (CONTINUED)