Field Excursion Flashcards
Ground Subsidence is associated with groundwater ______
piping
Strawberry Hill
recharge area for this region of S. Sask River
-mostly made up of clays overlain with sand
Geological Layers(3)
Till clay–>lake sand–>lake clay= trapped aquifer
Gully
a water-worn ravine.
terrace
In geology, a terrace is a step-like landform. A terrace consists of a flat or gently sloping geomorphic surface, called a tread, that is typically bounded one side by a steeper ascending slope, which is called a “riser” or “scarp.
Tilted trees show ________ is active
soil creep:
- is the slow downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress
- associated with frost creep/heave
Stratigraphy of Riverbanks
Glacier stopped about 12,000 years ago in its retreat and dammed the river creating:
- underlying late cretacious(shale) covered in glacier tills(clay) that doesnt translate water, then covered in lake clay
- upper sand layer percolates water but ponds on contact between sand and clay causing an increase in pore water pressure
Shale–>Till Clays–>Lake Clays–>Sand
Higher pore water pressure in sand layer and toeslope erosion by river itself which steepens slope eventually results in ________
rotational slump
Hospital was put on the CREST OF THE HILL WHICH IS BAD BECAUSE YOU SHOULD NEVER PUT ALOT OF WEIGHT ON THE CREST OF THE HILL because engineers mitigated the risk by…
placing footings all the way into the bedrock(shale) layer
What happened to Presedents lawn?
- trace of two large rotations slumps in 1990’s because of soil creep
- caused by water being put on lawns which moved through the sand layer
- solution was xeroscaping
- groundwater springs are being drained though pipes also
Why were retaining walls a failure?
-bare soil with no vegetation meant as surface flow(water) eroded soil away and have made the walls almost useless
2 things the government did to stabilize the slope?
- Regraded the slope(changed slope angle)
2. Planted large woody vegetation adding cohesion to the slope
Roads and houses are being damaged on the edge of the river because of ______ which are still growing
-what was the big solution?
tension cracks
enourmous headwall, big coffer dam with steel pipes and sheets to hold it in place
Why has the city’s mitigation tactic under the bridge of bring tons of boulders for armour somewhat failed?
- all it does is send eroding energy down the river
- it does prevent toeslope erosion in that one spot
